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Sun

Sun

Of all of the astronomical objects, the Sun is the most important to human beings. Since the dawn of civilization, knowing the daily and annual behavior of the Sun has meant the difference between life and death for people learning when to plant crops and when to harvest. Ancient mythologies preserved this knowledge in story form. These were often picturesque descriptions of the Sun's behaviorfor example, the Chinese interpretation of a solar eclipse as a dragon chasing and eating the Sun. Sometimes the stories included precise enough details for predicting solar behaviorfor instance, in the version from India, the dragon is sliced into two invisible halves. When the position in the sky of one of these halves is lined up with the Sun and the Moon, an eclipse occurs.

Solar Eclipses

Over centuries of observations and study, a scientific understanding of the Sun has grown out of these myths. The invisible dragon halves were a way of describing the serendipitous arrangement of the relative locations and sizes of Earth, the Moon, and the Sun. In order for a solar eclipse to happen, the Moon not only has to be in new phase (between the Sun and Earth) but also has to line up exactly with the disk of the Sun. Since the Moon's orbit around Earth is tilted with respect to Earth's orbit around the Sun, this happens about twice a year instead of once a month. Solar eclipses are not visible all over Earth, but only under the moving shadow of the Moon. In areas not completely covered by the Moon's shadow, observers see a "partial eclipse," which looks like a bite has been taken out of the Sun. Or, if the Moon is in the far reaches of its orbit it might not be quite big enough to cover the Sun's disk. Then observers would see the Sun shining in a thin, bright ring around the Moon in what is known as an "annular eclipse," even if they are perfectly lined up. Total eclipses of the Sun are rarely seen, because the timing and geometry have to be just right to position a large enough Moon-shadow right over a particular location. When this happens, observers in that location have an opportunity to observe parts of the Sun that are usually impossible to see.

Solar Corona

It is when the Sun is totally eclipsed that the solar corona is visible. "Corona" means "crown," and indeed the outer atmosphere of the Sun appears to encircle its blacked-out disk in an extended pearly crown. Ordinarily, the corona is so much dimmer than the bright disk of the Sun that it cannot be seeneven during a partial or annular eclipse. There is another way to see the corona, however, even without an eclipse. Although the part of the Sun seen with the naked eye normally outshines it, the corona is actually the brightest part of the Sun when observed with an X-ray telescope. The Sun emits light at a wide range of frequencies , or colors. Most of the light it emits is in the range visible to human eyesthe colors that make up a rainbow. Human eyes have actually adapted to be sensitive to the frequencies at which the majority of the sunlight shines. X rays are light emitted at much higher frequencies than humans can see, in the same way as a dog whistle blows at a frequency that is beyond the sensitivity of the human ear. An X-ray telescope filters out all the light from the Sun except X rays, and what is left is mostly the solar corona.

Because the corona shines in X rays we know it is very hot. This is strange. It means that although the temperature of the Sun decreases from its center out to its surface (from several million degrees Celsius down to several thousand), it increases again in the corona (up again to several million degrees). How and why the corona gets heated is one of the big mysteries of solar physics. It probably has to do with the energy that comes from magnetic fields generated inside the Sun, which is dumped into the corona, heating it up.

Sunspots and Magnetic Fields

Besides the more obvious daily and annual variations of the Sun, an approximately eleven-year cycle was discovered once people started observing with telescopes. This was first seen by counting the number of sunspots on the Sun. Sunspots are dark regions on the solar surface that are fairly infrequent during the minimum phase of the eleven-year solar cycle, but that become more and more common during the maximum phase. They are dark because they are cooler than their surroundings, and they are cool because they are regions of very strong magnetic field where less heat escapes the solar surface.

Sunspots are not the only solar features that are most abundant at solar cycle maximum. Explosive flashes known as "solar flares," and massive eruptions of material out from the Sun known as coronal mass ejections also become more and more frequent. The material that is hurled outward in a coronal mass ejection can affect us here on Earth, damaging satellites and even power stations, and potentially causing blackouts or disrupting satellite TV or cell phone transmissions. Like sunspots, flares and coronal mass ejections are related to solar magnetic fields. In general, magnetic activity increases at solar cycle maximum.

Magnetic fields are an important part of almost everything that is observed about the Sun. So where do they come from? The motions of sunspots provide a clue. Like Earth, the Sun is spinning so it has its own north pole, south pole, and equator. As they move around as the Sun spins, sunspots near the solar equator return to their starting point in about twenty-five days. Sunspots near the north and south pole of the Sun, however, take about thirty-five days to spin all the way around. The reason for this difference is that the Sun is not solid like a baseball, but fluidmore like a water balloon. Just below the surface this fluid is vigorously boiling and churning around, and this motion causes different parts of the Sun to spin around at different speeds. Furthermore, all this churning and spinning creates a magnetic field that is pointing one way near the north pole of the Sun and the opposite way near the south pole, like a giant bar magnet. Every eleven years, this magnet flips upside down so that in twenty-two years it has flipped over twice and is back where it started. Solar minimum happens when the magnet is pointing either due north or due south, and solar maximum occurs while it is in the process of flipping over.

Inside the Sun

When we look at the Sun, we see only the outside; how do we know what is happening below the surface? It turns out we can use techniques that are similar to those used in studying earthquakes. The surface of the Sun is continuously vibrating like a never-ending earthquake or a bell that is constantly being rung. By looking at the pattern of these vibrations and their frequency (like the tone of the bell), we can figure out what the inside of the Sun must be like. Thanks in part to these vibrations, we can confidently say that the churning motions below the surface not only create magnetic fields and make the Sun spin at different speeds, but they also move heat from the center of the Sun to the surface, where it is radiated away as light.

Near the center of the Sun the churning motions stop and the fluid becomes very dense and hot. Hydrogen atoms fly around at incredible speeds and when they collide they can stick together, creating helium atoms. This process, which is called fusion, provides the energy that causes stars to shine. In some stars, fusion can convert hydrogen and helium into heavier elements, such as carbon, oxygen, and nitrogen, which can in turn be combined to make still heavier elements, such as iron, lead, and even gold! In fact, everything on Earthair, water, dirt, rocks, buildings, cars, trees, dogs, and even peopleis made of elements that were created in stars by fusion.

The Evolution of the Sun

As exciting as it is, the Sun is often referred to as an "ordinary" star. This means that the information gained from the vast array of solar observations can be applied to understanding many of the stars in the sky. Furthermore by studying similar stars at various stages of their lifetimes, astronomers can tell how the Sun formed and how it will eventually die.

The Sun and the solar system began as a huge clump of gas in space, mostly made of hydrogen with some helium and only a relatively small amount of everything else (carbon, oxygen, iron, etc.). This clump slowly condensed and heated up due to gravity, and eventually it became dense and hot enough that fusion began and it started to shine. Not all of the gas fell into the young Sun; some of it stayed behind and was flattened into a pancake-like disk because it was spinning (just as a skilled pizza cook can flatten a clump of dough by tossing and spinning it). This disk then broke up into smaller clumps, which eventually became Earth and the other planets. Meanwhile, the Sun settled down to a quieter life, slowly converting hydrogen into helium by fusion and shining the energy away into space. That was about 5 billion years ago and the Sun is still going strong.

The Sun's Future

But that is not the end of the story. Eventually, there will not be any hydrogen left in the center of the Sun to make helium. Gravity will then cause the center part of the Sun to collapse in on itself, and the energy given off by this implosion will cause the outer part to inflate. So, while the inner part of the Sun shrinks, the outer part will expand, and it will become so big that it will envelop Mercury, Venus, and even Earth.

The Sun will then continue its life as a red giant star, but not for long. As its last hydrogen is used up, the center of the Sun will heat up and start to convert helium into other elements in a last-ditch effort to keep fusion going and to keep shining. The available helium will be used up relatively quickly, however, and before long all fusion in the center will stop. The outer part of the Sun will then slowly expand and dissipate into space while the inner part will become a white dwarf, a relatively small, inactive lump of matter, which will slowly cool down as it radiates all its remaining energy into space. Life on Earth would not survive these eventsbut as this terrible fate is not due to happen for another 5 billion years, we have plenty more time to study the Sun in all its splendor!

see also Cosmic Rays (volume 2); Solar Particle Radiation (volume 2); Solar Wind (volume 2); Space Environment, Nature of (volume 2); Stars (volume 2); Weather, Space (volume 2).

Sarah Gibson and Mark Miesch

Bibliography

Golub, Leon, and Jay M. Pasachoff. The Solar Corona. Cambridge, UK: Cambridge University Press, 1997.

Krupp, Edwin. C. Echoes of Ancient Skies: Astronomy of Lost Civilizations. New York:Harper and Row, 1983.

Phillips, Kenneth J. H. Guide to the Sun. Cambridge, UK: Cambridge University Press, 1992.

Strong, Keith. T., et al., eds. The Many Faces of the Sun: A Summary of the Results from NASA's Solar Maximum Mission. New York: Springer-Verlag, 1999.

Taylor, Peter O. and Nancy L. Hendrickson. Beginner's Guide to the Sun. Waukesha, WI: Kalmbach Publishing Company, 1995.

Taylor, Roger. J. The Sun as a Star. Cambridge, UK: Cambridge University Press,1997.

Internet Resources

Mr. Eclipse. <http://www.MrEclipse.com/Special/SEprimer.html>.

Solar and Heliospheric Observatory. <http://sohowww.nascom.nasa.gov/>.

The Stanford Solar Center. <http://solar-center.stanford.edu>.

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Sun

Sun

The Sun, the star at the center of our solar system, is an average-sized, middle-aged star. It is a gas ball made mostly of hydrogen and helium, with a small amount of carbon, nitrogen, oxygen, and trace amounts of heavy metals. The Sun is roughly 865,000 miles (1,392,000 kilometers) in diameter, about 109 times the diameter of Earth. The Sun, so large that more than 1.3 million Earths could fit inside of it, accounts for about 99.8 percent of the mass of the solar system.

Because the Sun is a gas ball, the rate of its rotation about its axis variesit spins faster around its equator than around its poles. At its equator, it completes one rotation in about 25 Earth days. At its poles, one rotation takes place about every 35 Earth days. The Sun's surface gravity is almost 28 times that of Earth. Its gravitational attraction holds all the planets, comets, and other solar system bodies in their orbits.

The solar core

The Sun's core is located about 312,000 miles (502,000 kilometers) below the surface. With a diameter of 240,000 miles (386,160 kilometers), the core accounts for only about 3 percent of the Sun's volume. Yet it is so dense that it contains about 60 percent of the Sun's mass.

The temperature in this dense area is an incredible 27,000,000°F (15,000,000°C). It is here that nuclear fusion, the Sun's heat-producing process, takes place. Under tremendous pressure and heat, two hydrogen nuclei are combined to form one helium nucleus, releasing a tremendous amount of energy in the process. The amount of helium found in the Sun indicates that the fusion of hydrogen to helium must have been going on for about 4.5 billion years. Scientists estimate that the Sun has enough hydrogen to continue producing energy for about 5 billion more years.

Words to Know

Chromosphere: Glowing layer of gas that makes up the middle atmospheric layer of the Sun.

Convection zone: Outermost one-third of the solar interior where heat is transferred from the core toward the surface via slow-moving gas currents.

Core: Central region of the Sun where thermonuclear fusion reactions take place.

Corona: Outermost and hottest layer of the solar atmosphere.

Flare: Temporary bright spot that explodes on the Sun's surface.

Granules: Earth-sized cells covering the Sun's surface that transfer hot gas from the Sun's interior to its outer atmospheric layers.

Nuclear fusion: Nuclear reactions that fuse two or more smaller atoms into a larger one, releasing huge amounts of energy in the process.

Photosphere: Innermost layer of solar atmosphere that constitutes the Sun's surface and where most of the visible light is emitted.

Plages: Bright hydrogen clouds on the surface of the Sun that are hotter than their surrounding area.

Prominence: High-density cloud of gas projecting outward from the Sun's surface.

Radiative zone: Central two-thirds of the solar interior.

Solar wind: Electrically charged subatomic particles that flow out from the Sun.

Sunspot: Cool area of magnetic disturbance that forms a dark blemish on the surface of the Sun.

Enveloping the core is a region called the radiative zone, in which heat is dispersed into the surrounding hot plasma (a substance made of ions [electrically charged particles] and electrons). Above the radiative zone is the convection zone, where heat is carried toward the surface by slow-moving gas currents. The temperature at the surface of the Sun is about 6,000°F (3,315°C).

The Sun's atmosphere

The atmosphere of the Sun consists of three general layers: the photosphere, the chromosphere, and the corona. Since these layers are composed of gases, no sharp boundaries mark the beginning of one layer and the end of another.

Photosphere. The photosphere, the innermost layer of the Sun's atmosphere, is a few hundred miles thick and has a temperature of about 10,800°F (6,000°C). When gas currents in the convection zone reach the photosphere, they release the heat they carry, then cycle back toward the center of the Sun to be reheated. The photosphere is covered with cells in which this heat transfer occurs. These cells, called granules, are Earth-sized chunks that constantly change size and shape.

Another feature of the photosphere is the presence of sunspots, dark areas that may exceed Earth in size. A sunspot has two components: a small, dark featureless core (the umbra) and a larger, lighter surrounding region (the penumbra). Sunspots vary in size and tend to be clustered in groups. They are magnetic storms caused by the transfer of heat stirring up the weak magnetic field lying beneath them. They are dark because they are 2,700°F (1,500°C) cooler than the surrounding area.

Chromosphere. Beyond the photosphere lies the chromosphere, another region through which heat and light pass from the inner layers to space. It is around 1,200 to 1,900 miles (1,930 to 3,060 kilometers) thick. At its greatest distance from the Sun's surface, the chromosphere has a temperature of about 180,000°F (100,000°C). This atmospheric layer is punctuated with plages and flares. Plages are bright patches that are hotter than their surroundings. Solar flares are sudden, temporary outbursts of light that extend from the outer edge of the chromosphere into the corona, the next layer. They produce an incredible amount of energy in only five to ten minutes. A flare can accelerate solar particles to nearly the speed of light. The largest flares generate enough energy to supply the United States's needs for 100,000 years.

Corona. The chromosphere merges into the outermost part of the Sun's atmosphere, the corona. The weak light emitted by the corona (about one-half the light of a full moon) is usually overpowered by the light of the photosphere and therefore is not detectable. During a solar eclipse, however, the Moon blocks the light of the photosphere and the corona can be seen shining around it.

The corona is the thinnest part of the atmosphere. It consists of low-density gas and is peppered with prominences. Prominences are high-density clouds of gas projecting outward from the Sun's surface into the inner corona. They can be more than 100,000 miles (161,000 kilometers) long and maintain their shape for several months before breaking down. The corona extends out into space for millions of miles. As its distance from the Sun increases, so does its temperature, to an incredible 3,600,000°F (2,000,000°C). Astronomers believe that the corona's energy may emanate from spectacular pillars of fiery gas near the Sun's surface, at the bottoms of looping arches of magnetic fields (like those produced by a bar magnet) that stretch for hundreds of thousands of miles above the surface. Hot gases seem to explode upward along the magnetic fields and heat the rest of the corona.

At its farthest reaches, the corona becomes the solar wind, a stream of charged particles (mainly free protons and electrons) that flows throughout the solar system and beyond. When the solar wind reaches Earth, the protons and electrons are flowing along at speeds up to 620 miles (1,000 kilometers) per second. Little of the solar wind reaches Earth's atmosphere because the charged particles are deflected by the planet's magnetic field. The particles that do get through spiral down toward the north and south magnetic poles where they collide with oxygen and nitrogen molecules present in the upper atmosphere. As a result of this collision, the molecules become ionized (electrically charged) and emit the shimmering, green or red curtains of light known as auroras (aurora borealis in the Northern Hemisphere and aurora australis in the Southern Hemisphere).

Solar activity cycle

The solar activity cycle is the periodic variation in active features such as sunspots, prominences, and flares in the Sun's atmosphere and

on its visible surface. Sunspot activity generally follows an 11-year cycle from the time when the number of sunspots is at a maximum to the next. During Solar Max or solar maximum, the Sun's magnetic north and south poles flip or reverse. Also accompanying the variations in sunspot number are corresponding changes in prominences and flares. An increase in all of these solar activities increases the solar wind and other matter ejected by the Sun. This, in turn, increases the appearances of auroras in Earth's atmosphere and also causes radio communication interference.

In April 2001, at the peak of the Sun's solar activity cycle, a solar flare erupted from the surface of the Sun near a giant sunspot that was 14 times as large as Earth. According to scientists, the flare was more powerful than any detected in the previous 25 years. Most of the blast was directed away from Earth. Still, two days after the flare erupted, luminous arcs, streamers, veils, rays, and curtains of light were seen in the night sky above Earth. Fortunately, sensitive electrical and communications systems were spared.

The Sun's end

About 5 billion years from now, the Sun will have used up all of its hydrogen fuel and will swell into a red giant, taking on a reddish color as its temperature begins to drop. Because the Sun will shed a great deal of its mass, Earth may be lucky enough to escape being swallowed up in its outer atmosphere, a 3,000°F (1,650°C) plasma. Even though Earth's orbit will be pushed slowly out into the solar system, the oceans will boil off, the atmosphere will evaporate, and the crust may melt. Earth will be a burnt ember. Eventually, the Sun's atmosphere will float away, leaving only a glowing core called a white dwarf that will cool for eternity.

[See also Nuclear fusion; Solar system; Star; Stellar magnetic fields ]

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Sun

Sun


The Sun is located in the "suburbs" of the Milky Way galaxy, around 30,000 light-years from the center and within one of its spiral arms. It revolves around the galaxy's center at an average speed of 155 miles per second, taking 225 million years to complete each circuit.

Although the Sun is just one star among an estimated 400 billion stars in the Milky Way galaxy, it is the closest star to Earth. More importantly, it is the only star that provides Earth with enough light, heat, and energy to sustain life. Also, the strong gravitational pull of the Sun holds the Earth in orbit within its solar system.

Many people forget that the Sun is a star because it looks so big and different when compared to other stars and because the Sun appears in the sky during the day, whereas other stars only appear at night. Because the Sun is so close to the Earth, its luminosity (brightness) overwhelms the brightness of other stars, drowning out their daytime light.*

*Because of its relative nearness, the Sun appears about 10 billion times brighter than the next brightest star.

Size and Distance

Archimedes (287 b.c.e.212 b.c.e.) placed the Sun at the center of the solar system. Observations of Galileo (15641642) supported this heliocentric theory, nullifying the ancient belief that the Earth was the center of the solar system.

Before the Sun's distance was known, Aristarchus (310 b.c.e.230 b.c.e.) knew that the Moon shines by reflected sunlight. Aristarchus decided that if he measured the angle between the Moon and the Sun when the Moon is half-illuminated, he could then compute the ratio of their distances from the Earth. Aristarchus estimated that this angle was 87, resulting in the ratio of their distances at sin 3°.

Before the invention of trigonometry, Aristarchus used a similar method to calculate the inequality , reasoning that the Sun was 18 to 20 times farther away from the Earth than the Moon. As calculations were refined, the angle between Moon and Sun was shown to be 89°50. Astronomers learned that the Sun is actually 400 times farther away from the Earth than the Moon.

Scientists now know that the Earth-Sun distance is 93 million miles. This distance was discovered when radar signals were bounced off Venus's surface to determine the Earth-to-Venus distance. At a speed of 500 mph, a journey from the Earth to the Sun would take 21 years.

Ancient civilizations thought that the Sun and Moon were the same size. Yet the Sun's diameter is really 864,338 miles across, which is more than 400 times the Moon's diameter and about 109 times the Earth's diameter. The Sun has a volume 1.3 million times the Earth's volume. Thus, a million Earths could be packed within the Sun. Although enormous compared to Earth, the Sun is an average-sized star.

German mathematician Johannes Kepler (15311630) devised his laws of planetary motion while studying the motion of Mars around the Sun. The Sun's mass can be calculated from his third law with the equation T 2 where T is the period of Earth's revolution (3.15 ×107 seconds), r is the radius of Earth's revolution (1.5×1011m), and G is the planetary constant (6.67 ×1011 Newton's m2/kg). To find M s (Sun's mass) insert these values into the equation and solve

Ms = (π)(1.5 × 1011m)3/(6.67 × 1011N m2/kg)(3.15 × 107s )2
       = 2.0 × 1030 kilograms.

Therefore, the Sun's mass is about 300,000 times the Earth's mass. Yet with respect to other stars, the Sun's mass is just average.

Time and Temperature

The Sun's rotation is similar to the Earth's rotation (one rotation every day), but because the Sun is gaseous not all parts rotate at the same speed. Galileo first noticed that the Sun rotates when he observed sunspots moving across the disk. He found that a particular spot took 27 days to make a complete circuit. Later observations found that the Sun at its equator rotates in slightly over 24.5 days. At locations two-thirds of the distance above and below the equator, the rotation take nearly 31 days.

In order to support its large mass, the Sun's interior must possess extremely large pressures and temperatures. The force of gravity at the core's surface is about 250 million times as great as Earth's surface gravity. No solids or liquids exist under these conditions, so the Sun's body primarily consists of the gases hydrogen (73 percent) and helium (25 percent).

Within the Sun's core, nuclear fusion reactions release huge amounts of energy. About 5 billion kilograms of hydrogen convert to helium, releasing energy each second. The core temperature is about 15 million kelvin, with a density of 160 grams per cubic centimeter. Based on mathematical calculations, the solar core is approximately the size of Jupiter, or approximately 75,000 to 100,000 miles in diameter. The amount of hydrogen within the Sun's core should sustain fusion for another 7 billion years.

For now, the Sun is bathing the Earth with just the right amount of heat. High-energy gamma rays (the particles created by fusion reactions) travel outward from the core and ultimately through the outer layers of the photosphere , chromosphere , and corona , losing most of their energy in the process. Along the way to the Sun's surface, the temperature of the gamma rays has dropped from 15 million to 6,000 kelvin. Yet even at these temperatures, the Sun is in the middle range of stellar surface temperatures.

Measuring the Sun

Information available about the Sun has increased with revolutionary scientific discoveries. Early telescopic observations allowed scientific study to begin, showing that the Sun is a dynamic, changing body. Later developments within spectroscopy, and the discovery of elementary particles and nuclear fusion, allowed scientists to further understand its composition and the processes that fuel it.*

*Astronomers now believe that the Sun is about 4.6 billion years old and will shine for another 7 billion years.

Recent developments of artificial satellites and other spacecraft now allow scientists to continuously study the Sun. Among the advances that have significantly influenced solar physics are the spectroheliograph, which measures the spectrum of individual solar features; the coronagraph, which permits study of the solar corona without an eclipse; and the magnetograph, which measures magnetic-field strength over the solar surface. Space instruments have revolutionized solar study and continue to add to increased, but still incomplete, knowledge about the Sun.

see also Archimedes; Galileo Galilei; Solar System Geometry, History of; Solar System Geometry, Modern Understandings of.

William Arthur Atkins with

Philip Edward Koth

Bibliography

Nicolson, Iain. The Sun. New York: Rand McNally and Company, 1982.

Noyes, Robert W. The Sun: Our Star. Cambridge, MA: Harvard University Press, 1982.

Washburn, Mark. In the Light of the Sun. New York: Harcourt Brace Jovanovich, 1981.

Internet Resources

"The Sun." NASA's Goddard Space Flight Center. <http://www-istp.gsfc.nasa.gov/Education/Isun.html>.

"Today from Space: Sun and Solar System." Science at NASA. <http://www.science.nasa.gov/newhome/pad/sun_today.htm#anchor1452757>.

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sun

sun the star round which the earth orbits and from which it receives light and warmth; it is the central body of the solar system and provides the light and energy that sustains life on earth, and its changing position relative to the earth's axis determines the terrestrial seasons.

In the ancient and medieval world, it was believed (in accordance with the Ptolemaic system) that the earth is the stationary centre of the universe. The heliocentric theory was proposed by the Polish astronomer Copernicus (1473–1543) in De Revolutionibus Orbium Coelestium (1543), and later supported by Galileo (1564–1642); although he was forced to recant by the Inquisition, the theory continued to gain ground.

The sun has been an object of worship in a number of religions, and has thus been personified as a male being, sometimes identified with a particular god, especially Apollo, who in classical mythology was believed to drive his chariot across the sky.

Proverbially the sun is a type of brightness and clearness, and in literary and poetic usage often stands for a person or thing regarded as a source of glory, inspiration, or understanding; the word may also be used with reference to someone's success or prosperity.

Recorded from Old English (in form sunne), the word is of Germanic origin, and comes ultimately from an Indo-European root shared by Greek hēlios and Latin sol.
never let the sun go down on your anger proverbial saying, mid 17th century, recommending a swift reconciliation after a quarrel; originally with biblical allusion to Ephesians 4:26, ‘Let not the sun go down on your wrath’.
sun in splendour in heraldry, the sun as heraldically blazoned, depicted with rays and often a human face; it was an emblem of the House of York.
Sun King a designation of Louis XIV of France, a translation of French roi soleil.
the sun loses nothing by shining into a puddle proverbial saying, early 14th century, of classical origin, meaning that something which is naturally clear and radiant cannot be tainted or diminished by association. The comment ‘the sun shines into dung but is not tainted’ is attributed to the Greek philosopher Diogenes, and Tertullian has, ‘the sun spreads his rays even into the sewer, and is not stained’.
Sun of Righteousness an epithet of Jesus Christ, after Malachi 4:2.
when the sun is over the yardarm originally in nautical usage, the time of day (noon) when it is permissible to begin drinking; the earlier variant when the sun is over the foreyard dates from the mid, and this from the late, 19th century.

See also happy is the bride that the sun shines on, make hay while the sun shines, nothing new under the sun, place in the sun.

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Sun

387. Sun

See also 25. ASTRONOMY ; 85. CLIMATE ; 100. COSMOLOGY ; 143. EQUATOR ; 245. LIGHT ; 318. PLANETS ; 417. WEATHER .

celidography
Archaic. a description of the surface markings on a planet or the spots on the sun.
coronagraphy
the observation of the corona of the sun by use of a telescope modifled to simulate an eclipse. coronagraphic, adj.
heliodon
an instrument used in astronomy to show the apparent movement of the sun.
heliography
1. the measurement of the duration and intensity of sunlight.
2. the system or process of signaling by reflecting the suns rays in a mirror.
3. an early photographic process involving coated metal plates exposed to sunlight. heliographer, n. heliographic, heliographical, adj.
heliolatry
the worship of the sun. heliolator, n.
heliology
Archaic. the science of the sun. heliologist, n.
heliomania
an abnormal love of the sun.
heliophobia
1. an abnormal fear of sunlight.
2. an avoidance of sunlight.
helioseismology
the study of motions of the solar surf ace.
heliotherapy
a method of treating illness by exposure to the rays of the sun.
pyrheliometer
an instrument for measuring the intensity of the suns radiation. pyrheliometric, adj.
radiometer
an instrument for measuring the intensity of radiant energy, composed of vanes which rotate at speeds proportionate to the intensity of the energy source. radiometric, adj.
radiometry
the measurement of radiant energy by means of a radiometer. radiometric, adj.
radiophony
the transformation of radiant energy into sound.
siriasis
1. sunstroke.
2. Obsolete, a sun bath or exposure to the sun for curative purposes.
solarism
1. the explanation of myths by reference to the sun or the personifi-cation of the sun, as the hero as sunfigure.
2. an overreliance on this method of interpretation. solarist, n.
solarium
a room designed and situated so as to receive the maximum amount of sunlight.

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sun

sun / sən/ • n. 1. (also Sun) the star around which the earth orbits. ∎  any similar star in the universe, with or without planets. 2. (usu. the sun) the light or warmth received from the earth's sun: we sat outside in the sun. ∎ poetic/lit. a person or thing regarded as a source of glory or inspiration or understanding: the rhetoric faded before the sun of reality. ∎ poetic/lit. used with reference to someone's success or prosperity: the sun of the Plantagenets went down in clouds. 3. poetic/lit. a day or a year: after going so many suns without food, I was sleeping. • v. (sunned , sun·ning ) (sun oneself) sit or lie in the sun: Buzz could see Clare sunning herself on the terrace below. ∎  [tr.] expose (something) to the sun, esp. to warm or dry it: the birds are sunning their wings. PHRASES: against the sun Naut. against the direction of the sun's apparent movement in the northern hemisphere; from right to left or counterclockwise. catch the sunsee catch. make hay while the sun shinessee hay1 . on which the sun never sets (of an empire) worldwide. place in the sunsee place. shoot the sun Naut. ascertain the altitude of the sun with a sextant in order to determine one's latitude. under the sun on earth; in existence (used in expressions emphasizing the large number of something): they exchanged views on every subject under the sun. with the sun Naut. in the direction of the sun's apparent movement in the northern hemisphere; from left to right or clockwise.DERIVATIVES: sun·less adj. sun·less·ness n. sun·like / -ˌlīk/ adj. sun·ward / -wərd/ adj. & adv. sun·wards / -wərdz/ adv.

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Sun

621. Sun (See also Light.)

  1. Apollo sun god; his chariot ride spanned morning to night. [Gk. Myth.: Benét, 42]
  2. Aton (Aten) solar deity worshiped as the one god by Amenophis IV. [Egypt. Myth.: Parrinder, 33]
  3. Bast cat-headed goddess representing sun and moon. [Egypt. Myth.: Parrinder, 41]
  4. Belenus sun god. [Celtic Myth.: Parrinder, 42]
  5. Buto goddess and mother of the sun and moon. [Egypt. Myth. Kravitz, 48]
  6. cock Helioss sacred bird; sacrificed to the sun in Mexico. [Rom. and Mex. Myth.: Leach, 239]
  7. Cuchulain sun-figure and powerful fighter. [Irish Myth.: Parrinder, 68]
  8. double ax symbol of the sun. [Hindu and Western Folklore: Cirlot, 22]
  9. eagle symbol represents the sun. [Gk. Myth.: Brewer Dictionary, 358]
  10. fire representation of the sun. [Western Symbolism: Cirlot, 105106]
  11. gold color of the suns rays. [Color Symbolism: Jobes, 357]
  12. Helios sun in its astronomic aspects; aspect of Apollo. [Gk. Myth: Espy, 28]
  13. Horns solar deity, portrayed as a hawk-headed man. [Egypt. Myth.: Benét, 478]
  14. Hyperion Titan and father of the sun. [Gk. Myth.: Zimmer-man, 132]
  15. lion symbol of the sun gods; corresponds to the sun. [Western Symbolism: Cirlot, 189190]
  16. Mithra (Mithras) god of sunlight. [Persian Myth.: EB, VI: 944945]
  17. Phaëthon Apollos son; foolishly attempted to drive sun chariot. [Gk. Myth.: Zimmerman, 202]
  18. Phoebus epithet of Apollo as the sun god. [Gk. Myth.: Benét, 42]
  19. Ra personification of the sun. [Egypt. Myth.: Parrinder, 235]
  20. Sol the sun god. [Rom. Myth.: Zimmerman, 245]

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sun

sun OE. sunne (fem.) = OS., OHG., ON. (poet.) sunna (Du. zon, G. sonne), Goth. sunnō, beside OE. sunna (m.), OHG., OS. sunno :- Gmc. *sunnōn, -an-; f. IE. *su- with n-formative, beside *sāu- with l-formative in Homeric Gr. ēélios :- sāwelijos (Attic hḗlios), L. sōl, ON. sól, Goth. sauil, W. haul.
Hence vb. XVI; sunny (-Y1) XIII. Comps. sunbeam OE. sunn(e)bēam. sunburn sb. XVII; f. the vb. (XVI), back-formation from sunburning (XVI), sunburnt (sunne ybrent XIV). sundew plant of the genus Drosera. XVI. tr. Du. son-, sundauw = G sonnentau, tr. L. rōs sōlis. sundial XVI. sundown setting of the sun XVII. perh. shortening of †sunne gate downe (XV), †sun go downe (XVI). sunflower †heliotrope; plant of the genus Helianthus, with showy golden-rayed flowers. XVI. tr. modL flōs sōlis XVI. sunrise XV. perh. evolved, through syntactical ambiguity, from a clause such as before the sun rise (pres. subjunctive of the vb.); cf. ME. sonne rist (XIII). sunset OE. (late Nhb.) sunset; perh. partly from a clause like ere the sun set. sunshade parasol. XIX. sunstroke XIX. For earlier stroke of the sun, tr. F. coup de soleil. sun-up (U.S.) sunrise XIX. After sun-down.

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Sun

Sun Star at the centre of our Solar System, around which all other Solar System bodies revolve in their orbits. The Sun is a typical, average star. It consists of c.70% hydrogen (by weight) and 28% helium, with the remainder mostly oxygen and carbon. Its temperature, pressure, and density increase towards the centre. Like all stars, the Sun's energy generates by nuclear fusion reactions taking place under the extreme conditions in the core. This core is c.400,000km (250,000mi) across. Energy released from the core passes up through the radiative zone, which is c.300,000km (200,000mi) thick, then passes through the 200,000km (125,000mi) thick convective zone to the surface, the photosphere, from where it radiates into space. Most of the Sun's visible activity takes place in this 500km (300mi) -thick photosphere. Above the photosphere lies the chromosphere, which consists of hot gases and extends for thousands of kilometres. Extending outwards from the chromosphere for millions of kilometres is the corona, which emits the solar wind. The solar wind and the Sun's magnetic field dominate a region of space called the heliosphere, which extends to the boundaries of the Solar System.

http://lpl.arizona.edu/nineplanets/nineplanets/sol.html

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Sun

Sun

The largest object in the sky, the sun is the source of light, heat, and life. It can also be a symbol of destructive power. Since earliest times, people in all parts of the world have observed the position of the sun and its rising and setting throughout the year. Many cultures have created solar calendars to govern such things as the planting of crops and the timing of religious festivals. They have also given the sun a major place in their mythologies, often as a deity.


Solar Deities. The pantheons of many cultures have included a sun deity, usually a god but occasionally a goddess. Some myths reflect the sun's vital role in supporting life: Solar deities are often creators who bring people into existence. Native Americans from the Pacific Coast, for example, tell how the sun god Kodoyanpe and the trickster Coyote together created the world and set about making people to live in it.

Solar deities have also been associated with fertility of people and the earth. The Hittites of ancient Turkey worshiped Arinna, an important goddess of both the sun and fertility. In traditional myths from Uganda in Central Africa, the creator god Ruhanga, the sun god Kazooba, and the giver of life Rugaba are all the same deity.

solar relating to the sun

deity god or goddess

pantheon all the gods of a particular culture

trickster mischievous figure appearing in various forms in the folktales and mythology of many different peoples

In some mythologies, sun gods have healing powers. Shamash, the solar god of the Babylonian* people of the ancient Near East, was known as "the sun with healing in his wings." Ancient Celtic* peoples had Belenus, the god of sunlight. Besides driving away the predawn mists and fogs each day, Belenus could melt away disease from the sick. When the Romans conquered the Celts, they identified Belenus with their own sun god, Apollo, who was also a god of healing.

As the most important and splendid deities of their pantheons, some solar deities have been associated with earthly rulers, the most powerful people in society. The Incas of Peru in South America regarded the sun god Inti, their chief deity, as the ancestor of the Inca royal family. According to Japanese tradition, the country's imperial family is descended from Amaterasu, the sun goddess.


Myths About the Sun. Some solar myths explain the sun's daily movement across the sky from east to west and its disappearance at night. Such stories often take the form of a journey, with the sun deity traveling across the heavens in a chariot or boat. Helios, a Greek solar deity later identified with Apollo, was a charioteer who drove his fiery vehicle through heaven by day. At night he floated back across the ocean in a golden bowl, only to mount his chariot again the next morning. The Navajo people of the American Southwest portray their sun god as a worker named Jóhonaa'éí, or sun bearer. Every day Jóhonaa'éí laboriously hauls the sun across the sky on his back. At night, he hangs the sun from a peg in the wall and rests.

The Egyptian sun god Ra made a similar circuit. Each day he traveled across the sky in his sun boat, and at night he passed through the underworld, greeting the dead and facing many dangers. Ra's daily cycle was more than a journey, thoughit was a daily rebirth. Dawn saw the newborn sun god rise in the sky. During the morning he was a child, at noon he was mature, and by sunset he was an old man ready for death. Each sunrise was a celebration of the god's return, a victory of life over the forces of death and darkness.

The Celts also viewed the sun's journey as a cycle of death and rebirth but on a yearly rather than a daily cycle, with midwinter as death and spring as rebirth. The Celtic celebration called Beltane, held in spring, honored their sun god Belenus.

underworld land of the dead

In some solar myths the sun is paired with the moon. The two may be husband and wife, brother and sister, or two brothers. In the mythology of many Native Americans, the sun god and moon god are sister and brother who also become forbidden lovers. The moon god's face is smeared with ash from the sun's fires, which accounts for the dark patches on the moon's surface. In some accounts, the moon flees in shame when he learns that his lover is also his sister. This is why the moon leaves the sky when the sun comes near.

Many cultures have myths of monsters or evil spirits that steal or devour the sun or stories of the sun falling from the heavens or withdrawing its light for a time. Some of these myths may explain eclipses, times when the earth's shadow temporarily blots out the sun or moon. A solar eclipse creates a period of eerie near-darkness in the middle of the dayan event that surely cried out for a reassuring explanation.

A well-known myth about the Japanese sun goddess Amaterasu tells how she became so angry with her brother, who was misbehaving, that she retreated into a cave. The goddess's withdrawal deprived the world of light and warmth. Finally, the other gods tricked her into emerging.

Too Many Suns

If one sun is good, are ten suns ten times better? Not according to the Chinese myth of Yi and the ten suns. Yi, a famous soldier, was an archer of great skill. At that time, ten suns lived in the Fu Sang tree beyond the eastern edge of the world. Normally the suns took turns lighting the earth, one sun at a time. The suns grew rebellious, and one day all ten of them rose into the sky at the same time. The extra light and heat pleased the people belowuntil their crops shriveled and their rivers began to dry up. The Lord of Heaven sent Yi, the divine archer, to handle the problem. Yi shot nine of the suns out of the sky.

According to a traditional myth from the Hindu Kush mountains of Afghanistan, the giant Espereg-era once stole the sun and the moon. The hero god Mandi disguised himself as a child and tricked the giants into adopting him. After a time with the giants, Mandi rescued the sun and moon and rode off with them on a magical horse. The supreme god then hurled them into the sky to shine on the world.

See also Amaterasu; Apollo; Aten; Inti; Lug; Mithras; Moon; Ra (Re); Shamash; Stars.

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Sun

Sun The central star (G spectral type) in the solar system, 696 000 km in diameter, 333 000 × Earth mass, 1 300 000 × Earth volume, and with a mean density of 1410 kg/m3. The equator is inclined at 7.25° to the plane of the ecliptic. It is principally composed of hydrogen and helium. The visible surface is the ‘photosphere’ (temperature 6000K). The Si-normalized solar abundances for the terrestrially non-gaseous elements match those of the C1 carbonaceous chondrites.

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Sun (river, United States)

Sun, river, c.130 mi (210 km) long, rising in the Rocky Mts., NW Mont., and flowing generally E to the Missouri River at Great Falls. The Sun River project of the U.S. Bureau of Reclamation utilizes the Sun and its tributaries to irrigate c.92,000 acres (37,230 hectares) of land. Of the system of dams and reservoirs, Gibson Dam is one of the project's largest.

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sun (in astronomy)

sun, intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the solar system in their orbits.

General Characteristics of the Sun

The sun is a star of about medium size; it appears so much larger and brighter than the other stars because of its relative nearness to the earth. The earth's distance from the sun varies from 91,377,000 mi (147,053,000 km) at perihelion to 94,537,000 mi (152,138,000 km) at aphelion (see apsis). The mean distance is c.92,960,000 mi (149,591,000 km); this is taken as the astronomical unit (AU) of distance used for measuring distances within the solar system. The sun is approximately 865,400 mi (1,392,000 km) in diameter, and its volume is about 1,300,000 times that of the earth. Its mass is almost 700 times the total mass of all the bodies in the solar system and 332,000 times that of the earth. The sun's surface gravity is almost 28 times that of the earth; i.e., a body on the surface of the sun would weigh about 28 times its weight on earth. The density of the material composing the sun is about one fourth that of the earth; compared with water, the sun's average density is 1.41. At its center, the sun has a density of over 100 times that of water, a temperature of 10 to 20 million degrees Celsius, and a pressure of over 1 billion atmospheres.

Observations of sunspots and studies of the solar spectrum indicate that the sun rotates on its axis from east to west; because of its gaseous nature its rate of rotation varies somewhat with latitude, the speed being greatest (a period of almost 25 days) in the equatorial region and least at the poles (a period of about 35 days). The axis of the sun is inclined at an angle of about 7° to the plane of the ecliptic.

The bright surface of the sun is called the photosphere. Its temperature is about 6,000°C. The photosphere appears darker near the edge (limb) of the sun's disk because of greater absorption of light by the sun's atmosphere in this area; this phenomenon is called limb darkening. During an eclipse of the sun the chromosphere and the corona (the outer layers of the sun's atmosphere) are observed. Also of interest is the high-speed, tenuous extension of the corona known as the solar wind.

Production of Solar Energy

The vast and continual production of solar energy cannot be attributed merely to combustion, to the gradual cooling of a hot body, to the fall of meteorites into the sun, or to gradual shrinkage with transformation of potential energy into heat (a theory proposed by Helmholtz). The theory of relativity with its implication of the equivalence of mass and energy led to the assumption that energy stored in the atoms constituting the sun's gases is constantly being released by conversion of some of the masses of the atom's nuclei during nuclear transmutations (see nuclear energy). H. A. Bethe proposed a cycle of nuclear reactions known as the carbon cycle, or CNO bi-cycle, to account for the nuclear changes. In this cycle carbon acts much as a catalyst, while hydrogen is transformed by a series of reactions into helium and large amounts of high-energy gamma radiation are released. It is now thought that the so-called proton-proton process is a more important energy source; this process begins with the collision of two protons and ends with the production of helium, while gamma radiation is released throughout.

See nucleosynthesis; stellar evolution.

The Study of the Sun

By means of the spectroscope much has been learned about the composition of the sun. There are numerous dark lines of varying widths in the solar spectrum. These were first intensively studied by Joseph Fraunhofer and are commonly known by his name. From a study of the lines the chemical composition of the sun is determined on the basis of the discovery by Kirchhoff that the dark lines correspond in position to the bright lines characteristic of the spectra produced by elements in the laboratory. The darkness of the lines in the sun's spectrum is attributed to the presence of a slightly cooler layer of gases above the photosphere, known as the reversing layer, which absorbs selectively the light of the photosphere and thus causes dark lines instead of bright ones to be observed through the spectroscope. By comparison of the sun's spectrum with laboratory spectra of incandescent elements, most of the elements known on earth have been identified in the sun's atmosphere.

Beyond the red portion of the visible solar spectrum is the infrared spectrum; for the study of these heat rays S. P. Langley invented the bolometer, a highly sensitive electrical device for measuring temperature. Solar heat and energy are measured by an instrument called the pyrheliometer. Other instruments devised especially for the study of the sun are the coronagraph and the spectroheliograph. These instruments and others have revealed a number of interesting phenomena occurring during the periods of solar activity associated with sunspots, e.g., faculae, plages (flocculi), prominences, flares, and coronal mass ejections (eruptions of charged particles into space).

Importance to Terrestrial Life

Without the heat and light of the sun, life as we know it could not exist on the earth. Since solar energy is used by green plants in the process of photosynthesis, the sun is the ultimate source of the energy stored both in food and fossil fuels. Solar heating sets up convection currents, and thus is the source of the energy of moving air. Falling rain also owes its energy to the sun because of the relation of solar radiation to the water cycle.

Bibliography

See K. Hufbauer, Exploring the Sun: Solar Science since Galileo (1993); R. Krippenhahn, Discovering the Secrets of the Sun (1994); K. J. H. Phillips, Guide to the Sun (1995); P. O. Taylor, Beginners Guide to the Sun (1996); S. T. Suess and B. T. Tsurutani, ed., From the Sun: Auroras, Magnetic Storms, Solar Flares, Cosmic Rays (1998).

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sun

sunbegun, bun, done, Donne, dun, fine-spun, forerun, fun, gun, Gunn, hon, Hun, none, nun, one, one-to-one, outdone, outgun, outrun, pun, run, shun, son, spun, stun, sun, ton, tonne, tun, underdone, Verdun, won •honeybun • handgun • flashgun •air gun • sixgun • popgun • shotgun •blowgun, shogun •speargun • scattergun • homespun •endrun • sheep run • grandson •stepson • godson • kiloton • megaton •anyone • everyone • someone

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Sun

SUN

SUN . There can hardly be anyone on earth who has not been profoundly aware of the apparent progress of the sun across the heavens and who has not related to it, either personally or as a numinous force. The rising and setting of the sun provides one of the primal dichotomies, parallel to those between day and night, light and darkness, warmth and cold, life and death, yang and yin. Night is mysterious, dangerous, akin to the darkness of the womb. Daylight symbolizes renewed life, truth, logic. In modern thinking, the sun often stands for individual consciousness, and the moon (or night) for the unconscious, the ocean, or the feminine principle. In children's drawings, a happy scene includes a huge round sun with rays like hair. Unhappy and frustrated children produce an entirely black sky. Mentally disturbed patients often draw their own bodies as the sun's disk, complete with arms and legs like rays.

In classical poetry birth is described as "reaching the shores of light." In the Eumenides of Aeschylus, the conflict is between the fearsome Furies, avengers of the mother's blood, who constantly invoke the "dark mother," and the shining Apollo, revealer of truth and righteousness (and symbolic of paternal predominance). The west, where the sun sets, in most rituals represents death; the east, where the sun rises, life and birth. Even Neanderthal burials were oriented according to east and west. When a Greek priest faced north in sacrifices, the right hand, stretched toward the east, represented the fortunate side, the left, the "sinister."

In many primitive mythologies, the sun is an object tossed up or hung in the sky by mortals or trickster figures. The Hopi Indians claim that they made their sun themselves, by throwing into the sky a shield made of buckskin together with a fox skin and a parrot's tail to make the colors of sunrise and sunset. The San of Africa believe that the sun was once a mortal who gave out light from his armpit. In order to make the light brighter, some children threw him into the sky, whereupon he became round and shines now for all humankind. Among the Tatars, the culture hero Porcupine took some fire on his sword and threw it up into the sky to make the sun. For the moon, he thrust his sword into the water; thus the sun is hot and the moon cool. The famous American Indian trickster Coyote is said to have sent the wolf to bring him fire to make the sun. In one of the Oceanic myths that describe life beginning inside a shell, the creator, Spider Woman, opened the shell and then threw up two snails to make the sun and moon. In Norse mythology the sun and moon are sparks from Muspelheim, the realm of fire. The gods, however, anthropomorphized them and set them to drive chariots across the sky.

In more sophisticated societies, the luminaries were set in the heavens by the high god. Sometimes, they represented his eyes. In ancient Egypt the sun was sometimes called the eye of Re; in northern Europe, the eye of Óðinn (Odin); in Oceania, the eye of Atea.

The creation myth of Mesopotamia, Enuma elish, relates how the conquering god Marduk, who had solar characteristics himself, "set up stations for the gods in the sky, determining the year by setting up the zones." According to the Book of Genesis "God made the two great lights, the greater light to rule the day, and the lesser light to rule the night. And God set them in the firmament of the heavens to give light upon the earth, to rule over the day and over the night, and to separate the light from the darkness" (1:1618). In Plato's great myth the Timaeus, "the Demiurge [the creator] lit a light which we now call the sun to shine through the whole heaven and to enable the living creatures to gain a knowledge of numbers from the uniform movements. In this way there came into being night and day, the period of the single most intelligent revolution" (39c). Thus the Demiurge, having set out all the heavenly bodies, put them in motion and brought time into being.

More often, the sun is anthropomorphized, sometimes as a female but more frequently as a male. He crosses the sky by the appropriate means of locomotion. In ancient Sumeria, he walked. In ancient Egypt, he sailed in a boat like the ones on the Nile, in company with some of the other gods and the pharaoh. When the horse was domesticated, about the beginning of the second millennium bce, the sun drove a chariot pulled by white or flaming horses. The horse, the sacred animal of the Indo-Europeans, was one of the animals most closely connected with the sun and was often sacrificed to it. Another creature associated with the sun was the birda falcon, raven, or eagle, or, of course, the fabulous phoenix, which dies and is born again from the fire every five thousand years. The wings of birds are attached to the sun's round form to produce the winged disk so common in solar iconography. In Africa and India the tiger and especially the lion are sun animals; in the Americas, the eagle and the jaguar. Leo is the zodiacal sign for the fiercest summer month; the lion is the royal animal on all the kingly architecture of the ancient Near East. The many representations of a lion attacking a bull may, some have surmised, reflect the heat of summer routing spring, represented in the zodiac by Taurus, the bull, or the paternal cult, attacking the female horned moon.

Eclipses of both sun and moon were experienced with great dread. The Tatars believed that an eclipse meant that the sun was attacked by a vampire who lived in a star. In Norse myth the sun was pursued by a supernatural wolf who will devour it when the world ends. The ancient Egyptians believed that a demonthe Chinese, a dragonwas attacking the sun. Some North American Indian tribes, on the other hand, believed that the sun and moon were eclipsed when they held their infants in their arms. In Tahiti it was believed that eclipses occurred when the sun and moon were mating.

Many devices were employed to "cure" eclipses, such as the beating of drums or the making of other loud noises or the shooting of arrows at the sun. "Snaring the sun" is one of the most widespread sun myths in Oceania and North America. This is one of the exploits of Maui, the Polynesian culture hero, for instance, who caught the sun and beat it so that it would not go so fast. It has been conjectured that stories of this kind are explanations for the solstices, when the sun is perceived to stand still for several days. The high cultures of the Inca and of Mesoamerican peoples were familiar with the stations of the sun, and the Pueblo measured sunrise points on the eastern horizon to divide the year. The Zuni used as a gnomon an erect slab with a solar effigy on top, and the sun temple at Cuzco, like Greek temples, was so oriented that the sun at the solstice would penetrate the shrine.

There seems to be no doubt that the impressive monument at Stonehenge in England was set up to mark the solstices and equinoxes as well as the stations of the moon. New carbon 14 readings indicate that Stonehenge is at least as old as the first pyramids, ruling out influence from the East on its construction. In view of the tremendous labor involved in moving and setting the megaliths, which occurred in three stages several centuries apart, there can hardly be any question that religious motivation was involved. Diodorus Siculus, writing in the first century bce, described a "spherical temple to Apollo among the Hyperboreans," which may be a reference to Stonehenge as a great temple to the sun. Recent research has turned up other observatories in Scotland, the Orkneys, and even in Carnac in Brittany. Gold and bronze disks engraved with crosses and spirals, daggers and horse trappings with the same designs, and amber disks with gold rims, all contemporary with the last phase of Stonehenge, have been found in the British Isles and in Scandinavia. It is tempting to imagine a crowd of people, each carrying a sun amulet, waiting for the summer sunrise at Stonehenge.

A spectacular object confirming northern sun worship is the famous disk found in Trundholm in northern Zealand, plated with gold and decorated with circles and spirals; it is set on wheels and drawn by a bronze horse, probably one of a pair. In all the Scandinavian countries have been discovered objects and rock carvings decorated with disks, boats, and scenes of humans raising their arms to a disk. Sometimes there are men in the shape of disks, carrying weapons. These have been interpreted as solar deities or mortals wearing the sun's emblem. The wheel, the boat, the cross in a circle, and the swastika (a moving wheel) can all be seen as sun symbols.

The summer solstice in northern Europe today is marked by bonfires and the rolling downhill of flaming wheels, as it was no doubt millennia ago. The winter solstice is a time to encourage the sun to grow again, represented by the burning of the Yule log, the anukkah light, and the lighted candles of Saint Lucy in Sweden. The boar's head at the Christmas feast represents the old year, or the old sun, and the suckling pig with the apple of immortality in its mouth is the new sun.

It was the tendency of nineteenth-century scholars to search for a single key to the understanding of all mythology. One of the most popular of these keys was the concept of the sun hero, a ubiquitous figure who was either the sun itself or an offspring of the sun. It has become clear over the years that all myths cannot be traced to one source. Yet there are some elements of myth that do seem to have solar references in common, perhaps formulated by the ancients at the time when astral religion invaded the Mediterranean world. It has been pointed out (by Joseph Campbell, for instance, in The Hero with a Thousand Faces ) that in most myths heroes have one divine parent and that they wander about on the earth and make at least one trip to the underworld. Also, most myths describe a wandering sun, which goes under or behind the earth at night, and in most myths the divine parent is perceived as a sun figure. One instance is the Greek Perseus, whose mother, an underground divinity, was impregnated by a shower of gold, the sun's metal. Another is the Irish Cú Chulainn, who is explicitly a son of Lugh Lamfhada, "Lugh of the long hands," an epithet that is reminiscent of the long rays that end in human hands pictured at Amarna in Egypt. Lugh was a god of brightness and the sky and, like Apollo, master of all crafts. He fought at the mythical battle of Moytura, where he vanquished his grandfather, the giant Balor, who had one eye in the middle of his forehead, like the cyclopes, who were also sun figures. The Welsh counterpart of Lugh is Lleu Llaw Gyffes, or Lludd. Lludd had a temple at Lydney in England near the Severn where he is portrayed, perhaps through Roman influence, as a young man with a solar halo driving a chariot. The Samson of Genesis, a mighty and short-tempered Herakles figure, has a name derived from the Hebrew word for "sun." Samson's fight with a lion, and his birth, which is connected with a supernatural figure who vanishes in flames, seem to point to other solar con-nections.

Homer's Odysseus has been interpreted as a sun figure, since he wanders for nine years, which is the period the Greeks used to correlate solar and lunar calendars. He finally reaches his Penelope, who weaves by day and unravels by night. Most replete with sun details, however, is the story of Herakles, son of the sky god Zeus, who wanders the earth to perform his deeds, returns unhurt from the underworld, dies in a fire, and is taken up to heaven. He not only lives on in heaven but also has a shade who lives on in the underworld. Herakles' labors were perhaps limited to twelve (although others have been recorded) in order to fit them into the zodiac.

As an all-seeing eye who travels the world, the sun acquired the character of a spy for the gods and therefore a stern judge of humankind. When the heavenly bodies began to be seen as parts of a well-ordered and consistent system, more pure and dependable than that of the old gods, the sun, an obvious leader in the sky, took his place as a symbol of the newly emerging royal power. Thus, organized cults of the sun are strongest in the great civilizations, which were often kingships. A new sense of power and organization, as well as a new sense of justice, found its central source in kingship, just as the harmony of the heavens was centered in the sun. "It is a remarkable coincidence," writes Jacquetta Hawkes, "that a discovery and an invention attendant on the creation of Bronze Age civilization came just in time to provide symbols of the sun gods and their temples. These were gold and the wheel" (Hawkes, 1962, p. 73). Since its discovery, gold has been the royal metal, as well as the sun's. The sun royal was adopted by all kings but never so completely as by the Sun King, Louis XIV (r. 16431715). Elizabeth II of England at her coronation in 1952 wore a golden gown under her robe, and her archbishop prayed that her throne "may stand fast in righteousness forevermore, like the sun before her and as the faithful witness in heaven." One must thus look to the high civilizations and imperial kingships to find the most highly developed cults of the sun.

Ancient Egypt

Very early in its history, somewhere in the fourth millennium bce, Egyptians broke away from a moon calendar and organized time around the heliacal rising of the star Sirius, which occurs about July 19. This date coincided with the yearly inundation of the Nile, the most important period in the agricultural life of a country that has no rainfall and no seasons. From that time on the year was divided into twelve months of thirty days each, with a five-day intraca-lendrical period. Whether or not this arrangement affected the religious life of the Egyptians, as some have argued, the sun in various aspects became the dominant figure in Egyptian religious life, combining with, and in some cases supplanting, other deities.

One of the earliest manifestations of the sun was the falcon god Horus, who appears on the famous palette of Narmer, the unifier of the two lands that became Egypt. Horus was probably an ancient sky god, seen as a soaring bird who was manifest in the sun itself; he was known as Re-Harakhty, the god of the horizon, or sunrise. He was at first the son of the sky goddess Hathor (in Egypt the sky is female and the earth male). Later, as the tendency to group the important gods into families developed, he was known as the son of Osiris, the god of fertility and the underworld. Osiris' sister-wife, Isis, mourns for her dead husband and secretly raises their son Horus to do battle with Osiris' murderer, his brother Seth. In this family, the sun god, Re, was combined with an older creator god, Atum. In Heliopolis, a temple compound just north of modern Cairo near the old capitol of Memphis, a powerful priesthood built up the cult of Re-Atum, beginning at least in the fourth dynasty (2600 bce). This is the period in which were built the first great pyramids, which pointed toward the sun. In the mythology developed at Heliopolis, the creator Re-Atum produced land from the surrounding waters. A mound in the temple was known as the Ben-Ben and was supposed to represent the semen of Re. Out of his own substances the creator god made sky and earth, air and water, and finally the four divinities: Osiris, Seth, and Isis and Nephthys, their wives.

The powerful priesthood at Heliopolis proclaimed the pharaoh the son of the Sun. It seems likely that the earlier pharaohs had themselves represented the Sun, and that they lost power under the growing influence of the priesthood. It was also possible for the priests to control the selection of the pharaoh's divine successor from among his offspring.

The history of ancient Egypt is neatly divided into the Old, Middle, and New Kingdoms, with two intervening periods of anarchy. After the first intermediate period, a new royal house arose in the south, at Thebes. There, Re was combined with a local god, Atum, the "Hidden One," probably representing the air. This god flourished throughout the New Kingdom, when Egyptian power spread into Asia. The great temples at Karnak and Luxor testify to the power and enormous wealth of the sun cult.

The sun was usually pictured as sailing across the sky in a boat, with various attendants and sometimes with the pharaoh himself. At other times the sun is seen sailing up the leg and belly of the sky goddess, who bends over the earth or straddles it in the form of a cow. Or the sun was swallowed at night by the sky mother and is born each morning from between her thighs. The sun was symbolized by a falcon but more notably by the mythical phoenix, which alighted on the Ben-Ben every five hundred years, was consumed in fire, and rose again. Another important symbol of the sun was the scarab, the dung beetle Khepri, which supposedly created itself by rolling its eggs in balls of dung. The obelisks, as well as the gold-topped pyramids, point toward the sun. On the early squat obelisk of the fifth dynasty, the sun is pictured as creator of life and lord of the seasons.

In the reign of Amunhotep III (14171439 bce), the actual disk of the sun, called the Aton, began to appear as a numinous symbol. It was the pharoah's son Amunhotep IV (13791362 bce), however, who attempted, in one of the great religious revolutions of history, to convert the entire nation to monotheistic worship of the Aton as sole god. Whether he was religiously motivated or whether he wished to break the power of the enormously wealthy priesthood, he sought to abolish all other worship in favor of the Aton, the sun's disk. He changed his name to Akhenaton ("Aton is satisfied") and built a new capital at Amarna. In this city he supported a new school of art, which pictured him in naturalistic style with his beautiful wife Nefertiti and his five daughters, all under the brilliance of the sun, which reached down to earth with long rays ending in human hands. Akhenaton has left a well-known hymn to the Aton as creator of all the beauties of the world: "How manifold are your works. They are mysterious in men's sight, O sole incomparable god, all powerful. You created the earth in solitude as your heart desires. Men you created, and cattle, whatever is on earth." Akhenaton's revolution failed, and after his mysterious death the priesthood reclaimed their power, and a young man (probably his son-in-law) resumed the worship of Amun, adopting the name of Tut-Ankh-Amun (or Tutankhamen).

Mesopotamia

In the land between the Tigris and Euphrates rivers, where are found the earliest traces of urban living, writing, kingship, and an organized priesthood, the sun was at first subordinate to the moon. To the first recorded inhabitants, known as the Sumerians, the chief god was An, a sky god who had retired from active control and left the rule of the universe to his son, Enlil, the Air. A son of Enlil was the important moon god, Nanna, whose children were the SunUtuand the Evening StarInanna. In Sumerian times, the regions were divided into a series of independent cities, each devoted to the worship of a patron god. Only two minor cities, Larsa and Sippar, worshiped Utu, the Sun.

The Semitic-speaking states that followed the Sumerians took over the religious organization they found, calling the moon Sin and the sun Shamash. In that dangerously torrid land, the sun was considered a baleful god. But since he traveled continually across the sky, he was considered a spy for the high gods and a stern judge of humankind. Travelers prayed to him before setting out on a journey, and armies before an expedition. He was thus a warrior god and leader of armies. In the quest of the hero Gilgamesh for the secret of immortality, it was the Sun who guided him on his journey. Originally the Sun walked across the heavens; in later times he rode a cart drawn by onagers, wild asses from the desert. Still later, the horse drew the Sun's chariot. The Sun in his chariot appeared in the morning at the eastern gate on the Mountain of Sunrise, in the evening arrived at the Mountain of Sunset, and then passed through to the underworld. Because of his appearance in the underworld, the Sun was sometimes pictured in company with Tammuz, the Mesopotamian dying god, who dies and is reborn. There was very little concern for judgment of the dead in Mesopotamia, and Shamash's character as judge was thus reserved for the upper world. At Ur, it was the Sun who punished a corrupt judge for taking bribes and oppressing the people.

Shamash was the god of oracles and was supposed to inscribe the signs that the diviners read in the intestines of sheep. Soothsayers claimed they were descended from a king of Sippar, who lived before the flood; the diviners were the most prestigious of the priests in that city of the Sun. From Assyrian times are preserved a number of questions asked of the Sun concerning the state and the royal family. The diviner read the answers in the entrails of dissected sheep. Probably a result of this activity was the Sun's power to control witches and demons.

Shamash was also invoked to heal the sick, free captives from bondage, and help women in labor. One prayer reads, "O Shamash, lofty judge may the knot that impedes her delivery be loosed may she bear. May she remain in life and walk in health before the godhead." The Sun, in other words, brings the unborn to light. He was also asked to deliver victims of spells, curses, and ghosts: "O Shamash, may I be strong and face the authors of my enchantment!"

The sun god is pictured as an old man with a long beard; sunbeams radiate from between his shoulder blades. He is seen sitting on a throne or sometimes on a horse. His special symbols are a four-pointed star in a disk with flames shooting out from between the points of the star and, of course, the winged disk, which was set above representations of royalty.

The study of heavenly bodies, conducted in Mesopotamia from at least 2000 bce, led to a belief in an ordered universe and in the important position of the sun among the planets. Thus, with the rise of centralized imperial power in Assyria and Babylonia, the sun came into prominence as a symbol of royal power. The lawgiver Hammurabi (c. 1750 bce) calls Shamash "great judge of heaven and earth" and proclaims that it was from Shamash that he received his laws. The sun god is seen seated on a throne, handing Hammurabi a ring and a staff. The sun temple at Babylon was known as "the house of the judge of the world."

Warlike Assyrians claimed Shamash as a great god of battles, almost the same as their own Ashur. Assyrian kings called themselves "suns of the world." Marduk, hero of the New Year festival at Babylon and a grandson of the high gods, is shown as a heavily bearded god with sun rays emanating from his shoulders. Thus the Sun in Mesopotamia, first perceived of as judge, lawgiver, and governor of magic, illness, and prophecy, grew into an image of the Sun Royal.

The Indo-Europeans

About the beginning of the second millennium bce, people speaking related languages spread across western Asia into Europe, bringing similar pantheons into India, Iran, Asia Minor, and most of Europe. Their high god was a sky godDyaus, Pitar, Zeus, or Jupiter. But in many cases this high god tended to fade out of the pantheon, leaving the universe to his offspring, sometimes the sun god. This process, known as solarization, brought the sun to the fore as creator and ruler of the gods.

The most cherished animal of the Indo-Europeans was the horse, and they perhaps introduced the chariot to the western world. From this time on the sun is pictured as driving a chariot across the sky, and the horse became one of the sun's animals, often sacrificed to him.

In ancient Indian and Iranian texts appear the names Varua and Mitra, which seem to mean respectively "the sky" and "the light of day." Mitra faded out in India, but in Iran, as Mithra, he was the subject of many hymns in the sacred writings, the Avesta. Mithra is said to represent celestial light, which appears before sunrise on the mountains, whence it crosses the sky in a chariot. He is said to be neither sun, moon, nor star, but with his hundred eyes he constantly keeps watch on the world. None can deceive him, so he is viewed as a god of truth and righteousness. He is the enforcer of oaths and contracts and is also called "lord of the wide pastures who giveth abundance and cattle." He combats the forces of evil, spies out his enemies, swoops down and conquers them, and is the ally of the faithful in their wars. Thus Mithra, though not identified with the sun, shares all the attributes of the Mesopotamian Shamash. When the Persians conquered Babylon the name Mithra was translated as Shamash. A large number of the names of Persian aristocrats are compounds of Mithra.

The Greek historian Herodotus relates that the Persians sacrificed to the sun as well as to earth, fire, and water and that leprosy was thought of as punishment for a sin against the sun (Histories 1.138). When Xerxes was leading his huge army through Asia Minor to attack Greece, he waited on the Asiatic shore until sunrise and then poured a libation from a golden cup, which he threw together with a golden scimitar into the sea (7.54). Xerxes' army was accompanied by a riderless chariot drawn by eight white horses, which Herodotus says was sacred to Zeus, the sky god. It was followed by a chariot of the sun, also drawn by white horses. Herodotus also tells us that along the route were led horses that were intended to be sacrificed to the sun. Horse sacrifices have been recorded from India to Ireland and have commonly accompanied the coronation of kings.

A true sun hymn occurs in the Avesta: "Unto the undying, swift-horse sun be propitiation and glorification. When the sun rises up, the earth, made by Ahura, becomes clean. Should the sun not rise up, the demons would destroy all things." Every layman in ancient Persia was required to recite a prayer to the sun at sunrise, at noon, and at three in the afternoon. Persian deities were established in Lydia, Cappadocia, and Armenia by Iranian officials, and it is probably through Persian influence that the sun god became prominent in places like Emesa, Baalbek, and Palmyra in Syria.

In India, the same divinities, Varuna and Mitra, are called in the gveda "kings of gods and men." They drive chariots across the sky and live in heavenly palaces with a thousand gold columns and a thousand doors. Ten hymns of the gveda are devoted to the sun under the name of Sūrya, who seems to represent the actual disk of the sun. Sūrya had the power to drive away darkness, witches, and evil dreams; he is also a healing god, particularly effective against jaundice. He is the husband of Dawn and drives a chariot, sometimes with one and sometimes with seven horses. Another name for the sun is Savit. Sometimes it is said that the sun is Savit before his rising and Sūrya afterward. Savit "brings all men and animals to rest; men lay down their work and birds seek their nests." Among other names given to the sun in the ancient poems is that of Viu, because "he strode across the sky in three giant steps" to ward off demons from humankind. Viu, of course, came to be one of the three great gods of Hinduism, the one especially benevolent to humankind.

Ancient Greece

In Hesiod's Birth of the Gods (c. 750 bce) Helios is the son of Hyperion, also a sun figure, and is the brother of the Moon (Selene) and of the Dawn (Eos). He is not included in the family of Olympians who came into prominence after Homer and Hesiod (from about 800 bce), but belongs to an older, less-well defined group that was closely connected with natural phenomena. In Homer (c. 800 bce), Helios reveals to Hephaistos the adultery of his wife, Aphrodite. In the Demeter myth he reports that Hades has carried off to the underworld Demeter's daughter, Persephone. The chariot of the sun is mentioned not in Homer but in the so-called Homeric Hymns (c. 700 bce). Demeter stands before the chariot as she begs for help. According to the Homeric Hymn to Helios, "as he rides in his chariot, he shines upon all men and deathless gods, and piercingly he gazes with his eyes from his golden helmet. He rests upon the highest point of heaven until he marvelously drives down again from heaven to the Ocean." The poet Mimnernus (c. 630 bce) describes the sun as floating back through the subterranean ocean in a golden bowl made for him by the divine smith Hephaistos. These descriptions laid the foundations for the hundreds of depictions of the sun in his chariot in Greek art, continuing into Roman times.

As in Mesopotamia, the Sun in Greece is involved in oaths and is a god of vengeance. In Aeschylus, Prometheus, bound upon his crag, calls upon "the all-seeing circle of the sun" to witness his woes. In Oedipus of Colonus, by Sophocles, Creon drives his brother-in-law out of the house so that "the sun may not look upon such a wretch." Cassandra in Aeschylus's Agamemnon calls upon the Sun for vengeance on her murderers. Medea in Euripides' play makes Aegeus swear by earth and sun that he will protect her. In the Argonautica of Apollonius Rhodius (third century bce) she swears by the Sun and Hekate. In the Iliad, 19.196, a boar is sacrificed to Zeus and the Sun in confirmation of an oath.

There was little direct worship of the sun in ancient Greece, though there are traces of earlier rites. Plato says the earlier Greeks made obeisance to the rising and setting sun. Pausanias in his guidebook to Greece (second century bce) mentions several shrines to the sun in remote places. For instance, the people of a little town north of Corinth, when suffering from a plague were told by the Delphic oracle to sacrifice a goat to the Sun. When they did, and the plague stopped, in gratitude they sent a bronze goat to the oracle, which many people, says Pausanias, thought was the Sun itself. Corinth itself was originally sacred to the Sun and, according to Pausanias, was called Heliopolis ("city of the sun"). Later the Sun gave the city to Aphrodite.

The island of Rhodes, however, had a true cult of the sun, influenced perhaps by the sun worship of the East. In legend, the island was brought up out of the sea to compensate Helios for his exclusion from the heavenly lottery. It was on Rhodes that Helios loved the nymph Rhoda and begot the seven wise men of the ancient world. An impressive festival of the sun, held on Rhodes every four years, included athletic games and a chariot race. Every year the Rhodians threw into the sea a chariot drawn by four horses. The famous colossus of Rhodes, one of the seven wonders of the world, erected in 284 bce, was a figure of the sun god. Pliny recounts that it was 105 feet high and that one of its fingers was larger than most statues. It was thrown down by an earthquake sixty-six years after it was erected.

In addition to being an all-seeing eye and god of vengeance, the sun in Greece has a connection with magic. Among his children were Aeetes, king of Colchis, Circe, the witch of the Odyssey, and Pasiphae ("all-shining"; perhaps a reference to the moon), who bewitched her husband, Minos of Crete. Most famous of the sun's lineage is Medea, daughter of Aeetes, whose enchantments form the plot of Euripides' play.

The Odyssey tells the story of the cattle of the Sun, which were taboo to mortals. They roamed on the island of Trinacria, seven herds of fifty each, tended by two daughters. Odysseus had been warned not to touch the cattle, but his marooned sailors were starving and killed and ate some. The flesh on the spits writhed and lowed. The Sun appealed to Zeus for vengeance and threatened to go down and shine in the underworld if he were not appeased. Zeus therefore hurled a thunderbolt, which destroyed the ship and left only Odysseus alive in the water. These cattle have been interpreted in various ways: Some say that they are the clouds that gather at sunrise and sunset, and Aristotle thought they stood for the days of the lunar year.

In ancient Greece, Apollo was a god of prophecy, sickness, healing, and death. He is connected by the historian Herodotus with the Hyperboreans, people of the north or east, who sent mysterious offerings to Apollo at Delphi. From the fifth century bce on, there are suggestions that link Apollo to the sun. The best known myth of the sun from ancient Greece is the story of Phaethon, who begged to drive the chariot of the sun, lost control of it, and would have scorched the earth if he had not been killed by a thunderbolt. In a fragment of Euripides, the mother of Phaethon says that the true name of the sun is Apollo, meaning "the destroyer," since he had destroyed her son. The Orphic poets, as well as the Cynic philosopher Crates (c. 300 bce), called the sun Apollo. Cornutus, writing about Greek mythology in the first century bce, says that the sun is Apollo and the moon is his sister Artemis. In Roman times, after the names of the Greek gods reached Italy, this identification was taken for granted. The first Roman emperor, Augustus, favored the worship of Apollo, built a temple to him on the Palatine, and had the poet Horace, in his secular hymns, speak of the sun as Apollo and the moon as Diana (identified often with Greek Artemis).

As the intellectual life of philosophy developed, the Olympians lost their appeal. Philosophers substituted for them the "visible gods," the fixed heavenly bodies. In Plato's Laws (10.3) Socrates prays to the rising sun. Star lore from Mesopotamia combined with Greek mathematics to produce astrology, which gave impetus to the tendency to believe that the heavens had a meaningful relationship with humans. Many philosophers opposed astrology, but the Stoics embraced it as an example of the pantheism they advocated. The sun was obviously the most important of the planets, and in the growing mysticism of the Roman era became the final destination of souls freed from the wheel of fate.

Ancient Rome

As in Greece, sun festivals are rare in ancient Rome, but there are indications of the early worship of Sol Indiges, that is, an original and native god. There was a public sacrifice to this god on the Quirinal on the ninth of August. Varro's book on agriculture (first century bce) says he will mention not the city gods but those who are the best guides of the farmer, the sun and moon, "whose seasons are observed at seedtime and harvest." Varro believed that the Sabine king Tatius, a contemporary of the founder Romulus, brought to Rome the worship of the sun and moon. He also stated that the ancient family of the Aurelii (whose descendants founded the cult of Sol Invictus) came from the Sabine country and that their name was originally Ausel, the Sabine word for "sun."

The sun and moon were deities of the chariot races. It is possible that the famous "October horse" ritual, held on the ides of October, was originally a sacrifice to the sun. This ritual involved a sacrifice of the outside winning horse; a similar ritual occurred in March, and thus these rituals marked the planting and the harvest seasons. The Sun had a temple on the Aventine near the Circus, from which spectators could watch the races. The Sun's image in gold was on the roof, since it was not proper to display the Sun indoors. It was to that temple that offerings were made when a conspiracy against Nero was revealed, since the Sun had discovered the plot (Tacitus, Annals 15.74). Augustus, returning from the conquest of Egypt, brought with him two obelisks with inscriptions declaring that he dedicated them to the sun, one of which he set up in the Campus Martius and the other in the Circus. They are now in the Piazza di Monte Citorio and the Piazza del Popolo.

Under the empire, various forms of sun worship spread into Rome from the East, imported both by slaves and by the Roman legions. The cult and mysteries of Mithra were the most widespread of these, apparently first taken up by soldiers of Pompey from Cilician pirates. The cult was obviously derived from the older Iranian cult, but from the two intervening centuries that separate these cults little is known about Mithra; the cult spread, however, to all areas of the empire. It involved initiation in a simulated cave; immortality was promised to initiates as a reward for the soldierly qualities of courage and discipline. Some astral features were collected along the way, and the degrees of initiation were known by the names of the planets. Mithra, who was said to be a special comrade or son of the sun, was born from a rock and sacrificed a bull, from which all creation sprang. After his deeds on earth were accomplished, he partook of a special love feast with the sun god before being carried up to heaven in a fiery chariot. The initiates imitated the love feasts in mithraea, underground shrines, which can still be found wherever the legions went. In death they were to be carried to the sun in Mithra's chariot. It became traditional for steles of the emperor to depict this journey upward in the sun's chariot.

One of the more lurid incidents in the late Roman empire involved the short reign of a young man who called himself Elagabalus, or Heliogabalus, after his god. A relative of Septimius Severus (r. 193211 ce) on his Syrian wife's side, the youth was the hereditary priest of a sun god who was worshiped at Emesa in Syria in the shape of a black meteorite. After the death of Severus and his son Caracalla, the ladies of the court contrived to have the youth named emperor, though he was then only fourteen years old. He brought his black stone to Rome and built for it a magnificent temple on the Palatine. In front of his temple every day the youth burned incense, poured wine, offered bloody sacrifices, andmost difficult for the Romans to acceptdanced Oriental dances. According to the time-honored fate of unsuitable emperors, the young man was assassinated after four years of rule.

The final victory at Rome of the sun god came about through the emperor Aurelian, who in 270 ce assumed the task of reconquering those parts of the empire that had defected. Aurelian's mother is said to have been a priestess of the Sun in the village in which he was born, from the old Sabine family of the Aurelii. The time was ripe for a new supreme deity who would symbolize imperial power, the person of the emperor, and the new astral religion. Aurelian found such a god in Palmyra, the oasis city in the Syrian desert. Aurelian dedicated a fortune in gold, silver, and jewels from his plunder to restore the temple of the Sun in Palmyra. In 274 ce he established Sol Invictus ("the invincible sun") as the official religion of the Roman empire, and was the first emperor to wear Oriental robes and the diadem, a sun symbol. Sol Invictus continued as supreme god and patron of emperors until Constantine, who started his reign as a sun worshiper and later turned the empire over to Christianity. The coins of Aurelian and of succeeding emperors show the Sun offering the ruler, as Preserver of the World, a globe. The Sun portrayed in these coins is not Oriental; he has the features of the Greek Apollo, wearing a crown with solar rays. Sometimes he drives a chariot drawn by four horses. Such coins read: "To the Invincible Sun, companion of Augustus."

Julian, called the Apostate, in his brief reign (359362) tried to bring back the worship of the sun. "From my childhood," he writes in his prose hymn to the sun, "an extraordinary longing for the rays of the sun penetrated my soul" (Hymn to King Helios 130c). The Neoplatonists, with whom Julian identified the leading philosophical school of the late empire, believed in one supreme ineffable god but were able to accept the sun as a symbol, "offspring of the first god." According to Julian, "His [Helios's] light has the same relation to the visible world as truth to the intelligible world" (ibid., 133a). Julian recognized three aspects of the sun god: the sun of the intelligible world, of the intellectual world, and of the sensible world, which last he identified with Mithra.

The birthday of Sol Invictus and of Mithra were celebated on December 25, close to the time of the winter solstice. In 353 or 354 ce Pope Liberius set this date as the Feast of the Nativity, and a few years later he founded the Church of Santa Maria della Neva, now known as Santa Maria Maggiore, which became the center of the Roman celebration of Christmas. The Nativity gradually absorbed or supplanted all the other solstice rites. Solar imagery came increasingly to be used to portray the risen Christ (who was also called Sol Invictus), and the old solar disk that had once appeared behind the head of Asian rulers became the halo of Christian saints. Excavations under Saint Peter's Basilica, undertaken in hope of finding the tomb of Peter, found a very early Christian mosaic that showed Christ driving a chariot, with rays above his head.

Japan

The national religion of Japan, Shintō, is an extraordinary combination of myth, national feeling, ancestor worship, and highly sophisticated mysticism. Japanese writers on the subject assert that theoretical analysis in the Western style is quite unsuitable for Shintō; it is rather a system of rites, feelings, and intense poetic appreciation. There is no doubt that the performance of the rites has over the centuries given the Japanese people a confidence in themselves and their place in society and the universe. The sun appears on the Japanese flag today, but the epithet "Land of the Rising Sun" was perhaps invented by the Chinese.

Japanese cosmogony, first recorded in the seventh century ce, relates how the islands came to be formed out of the primeval waters by a celestial couple, who gave birth to many other natural features. When the wife was burned and died in giving birth to fire, her husband, fleeing from the sight of her decomposing body, stopped to purify himself, and in the process produced from his right eye the Sun (female) and from his left eye the Moon (male). The Moon plays very little part in the mythology, but from the nose of the original husband was produced Susano-o no Mikoto, who represents violence, earthly qualities, and death, while the sun goddess, Amaterasu, stands for light and purity. Susano-o no Mikoto, realizing that the earth could only be created and peopled if the two powers cooperated, tried to force his way into the abode of Amaterasu, whereupon she hid in a cave and left the world in darkness. There are a number of caves in modern-day Japan that are identified as the cave where the goddess hid herself. Eventually the other gods persuaded Amaterasu to emerge. Among the sacred regalia they employed to ensure her emergence was a mirrorthe mirror that is said to be part of the ritual at the famous Ise Shrine.

Shintō teaching maintains that Amaterasu and Susano-o no Mikoto represent not good and evil but complementary qualities that are necessary to produce life on earth. Eventually the world as it stands was completed, and Amaterasu became the ancestor of the first emperor of Japan. The sun goddess is the center of Shintō worship, which is intended to bind the people together in reverence for her earthly representative. The goal of Shintō is the maintenance of harmony among humankind, nature, and the gods. The greatest reality visible in the heavens becomes the symbol of the greatest reality known and revered on earth.

The earliest records of Shintō derive from the seventh century bce, when writing was introduced, but the roots of the system may stretch much further back. In the Middle Ages, it was much influenced by Buddhism, but the two became distinct in the eighteenth century. In 1946, the American occupation forces demanded that the emperor renounce his divine status as part of their abolition of the state religion. It appears that the formal renunciation has had little effect on the symbolic relationship that has endured for centuries between the sun goddess and the imperial family. On the other hand, the retreat of state Shintō, which had highly politicized overtones and which was the basis for a fanatical militarism, in a sense returned the religion to the people. The priests, without government support, turned to the population. When it became time for the reconstruction of the Grand Shrine at Ise, which is prescribed every twenty years, there was an unprecedented outpouring of donations from the entire populace. More than fifty million people contributed to the rebuilding of the shrine in 1953, even more in 1973.

The rituals have continued and the emperor has participated in the divine nature of his ancestors by praying for the well-being of his people. In the great ceremonies at the end of June and December (the solstices), the imperial families and ministers of state pray for purification from sin for the entire country.

The Americas

Many native North Americans regarded the Sun as their supreme deity. In the Plains, the Crow thought of themselves as descendants of the Sun and swore by it. In lower Mississippi, the Natchez maintained a total theocracy; their priest-chieftain was a substitute on earth for their supreme being, the Sun. For the Pueblo, the Sun is a powerful deity but subordinate to others, such as the Corn Goddess. They perform ceremonies at the summer solstice to slow down the sun and at the winter solstice to hasten his progress toward spring. It is presumed that these rites are a projection of the same religion that is a basis for the sun cults of the high cultures of Mexico and Peru.

Mesoamerica

The Maya of Mesoamerica developed a complex civilization that to date has not been entirely revealed to modern researchers. There are still discoveries to be made in the huge structures now in ruins; they are probably not cities in a real sense but religious establishments where a priestly caste expended tremendous energies on mathematical study and on astronomical observations. They invented a sign for zero and produced two complicated calendars, which come together every fifty-two years. The site of one of their complexes was itself a huge calendar by which they could determine solstices and equinoxes. Since the Maya hieroglyphics have not been entirely deciphered, and since many of their sacred books were destroyed by the Spaniards, there is no clear picture of their complex religious pantheon, which involved four aspects for each deity (for the four points of the compass), or of the characteristics of their gods, which changed from one area to another. The supreme deity seems to have been a sky god, pictured as an old man with a Roman nose; he often performed as a sun god and was married to the Moon. Rain gods and fertility gods were also part of the pantheon. It is still unknown why the Maya civilization collapsed, although many theories, such as climactic change, conquest, or peasant revolt, have been suggested.

In the tenth century ce, conquering Toltec from Tula in central Mexico moved into Maya territory, took over the city of Chichén Itzá, together with many of the Maya achievements. The Toltec brought with them their culture hero, the Feathered Serpent, but also their belief that the sun god died every night and had to be resuscitated every morning with human blood. They established two priestly warrior groups, the Eagles, representing the sun in the daytime, and the Jaguars, representing the sun in the underworld. A frieze at Chichén Itzá from Toltec times shows members of the groups presenting a human heart to the sun. The sacrifice was often succeeded by a cannibalistic feast in which pieces of the victim, if he had been a great warrior, were passed out to the elite. A priest donned the skin of the victim and danced before the people.

The Toltec had perhaps been driven out of the valley of Mexico by the Aztec, who settled on islands in Lake Texcoco and built their elaborate city Tenochtitlán on the site that is today known as Mexico City. They took over from their predecessors the temple architecture, their fifty-two-year calendar, and the sacrifice to the sun, which they carried to even more grisly lengths. On some occasions as many as twenty thousand victims were sacrificed on the sun pyramid. The Aztec believed that on their journey north, their sun god, Huitzilopochtli, who took the form of a hummingbird, led them in the day, and the fearsome Tezcatlipoca, the sun of the underworld, led them at night. A third form of the sun represented the physical disk of the sun, under the name of Tonatiuh. He appears on the huge calendar stone, thirteen feet across, that is now in the Museo Nacional de Antropología. This stone pictures the four suns that the Aztecs believed had existed before them and the fifth, under which they lived. The former suns had been destroyed by storms, floods, and darkness, and the present sun, represented by Tonatiuh, was to end in an earthquake. The whole calendar is circled by fire serpents, which the Sun uses to fight his enemies at night. The entire religion of the Aztec was suffused with the battle between light and darkness and life and death. The universe, they believed, would fall into ruins if they did not feed the "skeleton" sun every morning as he rose.

It seems to have been the priesthood, possibly under the influence of psychedelic drugs, who drove the armies to seek increasing numbers of conquests in order to provide prisoners for the sacrifices. Huitzilopochtli is said to have proclaimed, "My principal purpose in coming and my vocation is war." All young Aztec were educated for war and taught to endure pain. There is a story told of the gladiatorial battle that followed the morning sacrifice in which a captive was tied to a stone and given four staves to defend himself against two Eagle and two Jaguar knights. Once, a captive miraculously won his battle and was released, but he returned to die on the stone so that he would not lose the privilege of accompanying the sun across the sky every morning. In the afternoon, the sun was followed by women who had died in childbirth, for they had also died "taking a man prisoner."

Peru

In Mexico the Sun became one of the most bloodthirsty of all divinities, but the sun god of the Inca of Peru was an autocratic but paternalistic deity, who planned for the welfare of his people while controlling their every action. In the high civilization of Peru, the sun again symbolized royal power; images of the sun were emblazoned with the most lavish display of the sun's metal ever seen. In Peruvian society there was no trade in (as there was among the Aztec) nor use for metal, except for extravagant adornment of the gods and royal personages.

A number of Spanish chronicles have recorded Inca rule as one of the most orderly and regulated in the world. All land was owned by the state and was divided into church, state, and peasant holdings. Inca territory was divided into four quarters ruled by governors, who were subordinate to the emperor, the son of the Sun. The emperor controlled the priesthood, usually making his brother high priest.

The leading tribes that formed the Inca empire seem to have arrived in Cuzco from somewhere around Lake Titicaca. Their legend told that the founder and his sister, children of the Sun, were set down by their father on an island in the lake. The first emperor is said to have been sent by his father, the Sun, to establish a city at the place where the golden wand the Sun carried struck the ground. This site was Cuzco, at eleven thousand feet above sea level. It was apparently the custom for each new emperor to build his own palace, so that the site became a maze of buildings, temples, and palaces, lavishly decorated with gold. In the main square, the Inca emperor himself was enthroned during festivals. From that square it was possible to see the sun columns on the hills east and west, markers of the solstices. The mummified figures of past emperors were seated, robed in gold, around the temple of the Sun, with their wives between them. The temple was called the Place of Gold and was so arranged that sunrise fell on a gold-sheathed solar disk and filled the whole temple with reflected light. On festival days the mummies were paraded around the city, preceded by the emperor on a palanquin, honored as if he were a god. Tradition held that the emperor married his sister, who represented the moon, but a large number of "virgins of the Sun" were available to him, so that he had many descendants. These were the "children of the Sun," the rulers of the bureaucracy, who paid no taxes. Others of the virgins were used for sacrifice or kept in seclusion, weaving or making brew.

The temple also housed the gods of conquered peoples, who were allowed to visit their gods and pay homage to them, although there was a strong missionary pressure on them to honor the sun god. By practicing efficiency and good military discipline, the Inca established an empire that stretched from Ecuador to northern Chile and that had just reached its height at the time of the Spanish conquest.

In the last century of the empire one of the Inca, by the name of Pachacuti, introduced a new high god, Viracocha, as creator. The legend relates that Pachacuti had a vision that prompted this religious revolution. He came to believe that the sun worked too hard on his daily journey to have created the universe. Viracocha may have been a local god from another tribe. Another possibility is that the new god was more acceptable to some of the conquered people, such as the Chimú of the coast, who worshiped the moon and the sea. It is recorded that they complained, "The sun is dangerous to us." A gold statue of the new deity was placed in the Sun's temple as an addition to its other resplendent embellishments.

Great Inca festivals consisted of dances, processions, prayers, and sacrifices, usually of llamas and guinea pigs but sometimes of human beings. The four chief festivals were those of the solstices and the equinoxes, the most important of which was the winter solstice. On this day, considered New Year's Day, all fires were relit by a piece of cotton kindled by the sun's rays. The relit fire was used for the sacrifices and then handed over to the Virgins of the Sun to be guarded until the next year. If the day was cloudy, the fire had to be kindled by friction and there was great anxiety among the people. At the summer solstice, the population gathered in the central square clothed in feathers and golden robes to watch the Inca emperor pour a libation to the Sun from a golden vase.

The priesthood, like all the other members of Inca society, were organized in a strict hierarchy. Many were engaged in divination and in curing the sick. They divined by reading the intestines of llamas and the flight of birds. To cure the sick, they engaged in rites of exorcism. Public confessions were an important part of religious life. Anyone who was malformed or had lost children was considered to have sinned against the Sun and to have disobeyed the Inca emperor. It was necessary for the sinner to confess; he would then be given a penance by the priest and be purified in running water. Anyone who did not confess was believed to be destined for a place deep in the earth where there were only stones for food. Those who confessed, as well as those who had led blameless lives, were promised a happy afterlife in the Sun's heaven. The Children of the Sun and the Inca emperor himself were, as a matter of course, believed to live with the Sun forever.

See Also

Amaterasu Ōmikami; Avesta; Light and Darkness; Mithraism; Saura Hinduism; Sol Invictus; Winter Solstice Songs.

Bibliography

Since there are few books devoted entirely to the religious and mythological aspects of the sun, most of the material must be extracted from religious writings, encyclopedias, and histories of the religion of the different regions. A highly respected source for ancient Rome is Franz Altheim's History of Roman Religion (New York, 1938). Of the many works on Egyptian religion, a good summary is Ann Rosalie David's The Ancient Egyptians (London, 1982). The Dictionnaire des antiquités grecques et romaines, vol. 4, edited by Charles Daremberg and Edmond Saglio (Paris, 1911) contains an article "Sol" by Franz Cumont, which treats both Greek and Roman sun worship with a wealth of detail. A comprehensive picture of the religion of Britain and Ireland can be found in Jan de Vries's Keltische Religion (Stuttgart, 1961). An essay called "The Sun and Sun Worship," in Patterns in Comparative Religion by Mircea Eliade (New York, 1958), provides many insights into various aspects of the subject. The article "Christmas," in the Encyclopaedia of Religion and Ethics, edited by James Hastings, vol. 3 (Edinburgh, 1910), details the many theories on the origin of the solstice festivals. A very lengthy chapter on the sun in James G. Frazer's The Worship of Nature (London, 1926) is packed with data from primitive sources and makes a point of criticizing the pansolism of the nineteenth century. In The Chariot of the Sun (New York, 1969) Peter Gelling and Hilda R. Ellis Davidson have produced a useful account of sun worship in the Bronze Age in northern Europe. Man and the Sun (New York, 1962) by the archaeologist and historian Jacquetta Hawkes is an accurate and sensitive treatment of sun worship in the ancient world and the Americas. Unfortunately, it does not contain a bibliography or notes. Jean Herbert, in Shintō (London, 1967), presents a worthy effort to make the Japanese cult available to the Western world. It contains many translations of ancient literature and more recent Japanese commentaries. In The Religions of the American Indians (Berkeley, 1979), Åke Hultkrantz gives a concise but thorough summary of the beliefs of the American Indians, both north and south. A work on astroarchaeology, In Search of Ancient Astronomies, edited by Edwin C. Krupp (Garden City, N.Y., 1978), treats, among others, the work of Atkinson, Hawkins, and Thom on the megaliths of the British Isles. The most recent and fullest account of the religions of the ancient Near East is to be found in Thorkild Jacobsen's The Treasures of Darkness: A History of Mesopotamian Religion (New Haven, Conn., 1976). An extremely useful collection of material from all over the world, both ancient and primitive, is the Mythology of All Races, 13 vols., edited by Louis H. Gray (Boston, 19161932), published under the auspices of the Archaeological Institute of America. Martin P. Nilsson brings to his Geschichte der griechischen Religion, 3d ed., 2 vols. (Munich, 19671974), a wealth of information from archaeology and comparative religion. Still the most complete collection of mythological material is to be found in Ausführliches Lexikon der griechischen und römischen Mythologie, edited by W. H. Roscher (18661890; Hildesheim, 1965), in articles entitled "Helios," "Sol," and "Sonnenkulten." The "Sacred Books of the East" series, containing the religious writings of India and Persia collected by F. Max Müller in 1884, has been reissued (Delhi, 1965). Maarten J. Vermaseren, in Mithras, the Secret God (New York, 1963), presents a detailed account of the cult of Mithra in the Roman world.

New Sources

Aldhouse-Green, Miranda. The Sun-Gods of Ancient Europe. London, 1991.

Bailey, Adrian. The Caves of the Sun: The Origin of Mythology. London, 1997.

Fideler, David. Jesus Christ, Sun of God; Ancient Cosmology and Early Christian Symbolism. Wheaton, Ill., 1993.

Goodison, Lucy. Death, Women, and the Sun: Symbolism of Regeneration in Early Aegean Religion. London, 1989.

Heilbron, J. L. The Sun in the Church: Cathedrals as Solar Observatories. Cambridge, Mass., 2001.

Hornung, Erik. David Lorton, trans. Akhenaten and the Religion of Light. Ithaca, N.Y., 1999.

Orcutt, William Tyler. Sun Lore of All Ages: A Collection of Myths and Legends Concerning the Sun and Its Ages. San Diego, Calif., 1999.

Saran, Anirudha. Sun Worship in India: A Study of the Deo Sun-Shrine. New Delhi, 1992.

Taylor, J. Glen, ed. Yahweh and the Sun: Biblical and Archeological Evidence for Sun Worship in Ancient Israel. Sheffield, U.K., 1994.

Titcomb, Sarah. Aryan Sun Myths: The Origin of Religions. San Diego, Calif., 1999.

Jean Rhys Bram (1987)

Revised Bibliography

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Sun

SUN

SUN (Heb., שֶׁמֶשׁ; poetical form חַמָּה; Isa. 24:23; 30:26; Song 6:10, et al.). A deity for Israel's neighbors, the sun is for Israel "the greater light to rule the day", created on the fourth day of creation (Gen. 1:16). In Joseph's dream, the sun and the moon personify his parents (Gen. 37:9–10). In Joshua 10:12–14, the sun is said to have stood still to give the Israelites time to defeat the Amorites.

Cult

In the Bible, the sun is either feminine or masculine in gender. As a deity it is masculine in Mesopotamia, and feminine in Ugarit, South Arabia, and other places. The Hittites worshiped a god and a goddess of the sun. Under the Sumerian name Uta or the Semitic Shamash, the sun, as the god of justice, was worshiped especially at the temple of Ebabbar in Sippar, in northern Babylonia. In the stele of Hammurapi's code from Susa, Hammurapi is depicted standing before Shamash who is seated on a throne (see Pritchard, Pictures, 175, no. 515).

The rare word for sun חֶרֶס (Job 9:7; cf. har ḥeres in Judg. 1:35, identical with ir shemesh in Josh. 19:41) has no known cognate in the Semitic languages.

The cult of the sun, very popular in Palestine – as is attested by place-names such as Beth-Shemesh, En-Shemesh, Ir-Shemesh – was forbidden in Deuteronomy 4:19 and 17:3. It was, nevertheless, introduced into Judah by Manasseh (ii Kings 21:3, 5). King Josiah abolished the cult (ii Kings 23:5) and destroyed the horses and chariots of the sun placed "by the kings of Judah at the entrance of the Temple" (23:11).

See Host of *Heaven; *Moon; *Sundial.

In the Aggadah

The usual word for "sun" in rabbinic literature is ḥammah, although shemesh also occurs. The sun and the moon were created on the 28th of Elul (pd-re 8). Although they were originally equal in size, jealousy induced dissensions between them, each claiming to be greater than the other. This necessitated the reduction in size of one of them, and the moon was chosen to be degraded because it had unlawfully intruded into the sun's domain. This is based on the phenomenon that the moon is sometimes visible while the sun is still above the horizon (pd-re 6; Gen. R. 6:3). Originally, the sun was designated as Jacob's tutelary luminary but later God assigned it to Esau, the moon being designated for Jacob. For this reason the Jewish people reckon by the lunar calendar (Gen. R. 6:3). It was God's original intention that the sun alone should furnish light to the earth. However, when He foresaw the future idolatrous worship of the heavenly objects, He decided that it would be better to have two large celestial bodies so that the danger of one becoming a central deity would be minimized (Gen. R. 6:1). For this reason, the sun and moon stand in judgment daily before God, ashamed to go forth, pleading "People worship us and anger the Holy One, blessed be He!" (Mid. Ps. to 19:11). When Joshua bade the sun stand still it first refused, but complied when Joshua said, "Faithless servant! Did not my ancestor [Joseph] see you in his dream, bowing down to him?" (Gen. R. 84:11).

God placed the sun in the second firmament because placing it in the one nearest the earth would have consumed all beings by its heat (Mid. Ps. to 19:13). Indeed, the sun is kept in a sheath. In the future, God will draw forth the sun from its sheath and the wicked will be consumed by its intense heat. Hence during that period there will be no Gehinnom (Ned. 8b). Simultaneously, the sun will heal the righteous of all ills, and will be a glorious ornament for them (Ned. 8b). The sun ascends by means of 366 steps, and descends by 183 in the east and 183 in the west. There are 366 windows in the firmament through which the sun successively emerges and retires. These windows are arranged so as to regulate the sun's movements in accordance with the tekufot ("seasons") of the year. The sun bows down before God and declares its obedience to His commands. Three letters of God's name are written on the sun's heart, and it rides in a chariot. One set of angels leads it by day and another set leads it by night (pd-re 6).

The rotation of the sun causes the emission of beams and rays just as dust is produced by sawing wood. The sound which the sun makes during its rotations would be heard were it not for the din of the city of Rome (Yoma 20b). The rabbis differ as to the color of the sun. One holds that its natural color is truly red as it appears at sunrise and sunset, yet it appears white during the day because its powerful rays dim the sight of man. Another says the sun is actually white, but it appears red in the morning when it passes through and reflects the red roses of the Garden of Eden, and also toward evening when it passes through and reflects the fires of Gehinnom (bb 84a). The Talmud deduces the healing efficacy of sunlight from the verse "But unto you… shall the sun of righteousness arise with healing in its wings" (Mal. 3:20; Ned. 8b). Abraham possessed a precious stone which healed the sick. When he died God set it in the sphere of the sun (bb 16b). Sunshine on the Sabbath is considered a blessing for the poor because they have the leisure time to enjoy its rays (Ta'an. 8b).

An eclipse of the sun is an evil sign for the gentiles while an eclipse of the moon augurs evil for the Jews. When the solar eclipse occurs in the eastern horizon it forecasts bad tidings for the inhabitants of the East; if in the western horizon it betokens ill to those of the West; while if it occurs in the zenith it threatens the entire world. When the color of the eclipse is red it symbolizes war; when gray, famine; when changing from red to gray, both war and famine. When the eclipse occurs in the beginning of the day or of the night it signifies that evil will come soon; if late in the day or night, then it will arrive tardily. Jews who are true to their faith need not worry about these premonitions since the prophet already said: "….be not dismayed at the signs of heaven, for the nations are dismayed at them" (Jer. 10:2; Suk. 29a).

See also *Sun, Blessing of.

bibliography:

Ginzberg, Legends, index.

[Alfred Rubens]

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Sun

Sun

A brief history of solar observations

A journey through the sun

The solar wind

A small blue planet

Resources

The Sun (or, sun) is the star at the center of the Earths solar system. As such, the Earth and seven other planets, several minor planets, and an assortment of meteorites, asteroids and other objects orbit around the Sun. It has a diameter of about 420,000 mi (700,000 km) and a surface temperature of about 9,981°F (5,527°C). Its visible surface is actually a thin gas, as is the rest of its atmosphere and interior. Astronomers estimate that the Sun is about 4.6 billion years old, and will continue to shine for another 7 billion years.

The Sun shines as a result of thermonuclear fusion reactions in its core, and the energy produced by these reactions heats the gas in the Suns interior sufficiently to prevent the weight of its own matter from crushing it. This energy is, also, the source of heat and life on the Earth, and small variations in the Suns energy output, or even in the features present in its atmosphere, may be sufficient to profoundly affect terrestrial climate. Although the Sun is by far the nearest star, the processes causing solar variability are still poorly understood and continue to challenge astronomers.

A brief history of solar observations

The Sun is about 90 million mi (150 million km) away from the Earth. It is modest by stellar standards, although it is over 100 times larger than the Earth and over 300,000 times more massive. Although it consumes more than half a billion tons of its nuclear fuel each second, it has been shining continuously for over 4.6 billion years, and it will continue to shine for another seven billion.

To the ancient Egyptians, the Sun was a god, for anyone who felt its warmth and watched the renewal of crops it brought in the spring realized it was a bringer of life. Greek mythology recounts the tale of Icarus, who died in a brazen attempt to fly too close to the Sun.

Ancient dogma held that the Sun orbited the Earth. It was not until 1543 that Polish astronomer Nicolaus Copernicus (14731543) published the heliocentric theory of the universe, in which the Sun lay at the center

and the Earth was relegated to a circular orbit around it. Copernicus refused to have this magnificent work published until near his death. This was a wise decision, since earlier publication would have no doubtedly resulted in his equally earlier death at the hands of Church authorities who regarded his work as heresy.

Around 1610, the newly invented telescope was trained on the Sun. The early solar observers, including Italian astronomer and physicist Galileo Galilei (15641642), noticed that the surface of the Sun had dark spots on it. Not only that, the spots moved across the solar surface, leading Galileo to conclude that the Sun rotated. This sent further shock waves through the religious world. The poor cardinals had hardly recovered from Copernicuss heresy, and now along came Galileo telling them that the backup embodiment of celestial perfection, the Sun, had ugly blemishes on its surface. Galileo got into serious trouble with the Church for this and other statements he made, and it would be 380 years before Pope John Paul II exonerated him.

In the nineteenth century, amateur German astronomer Heinrich Schwabe (17891875) did some of the first scientific analysis of solar data. Observers had kept records over the years of the number of sunspots visible, and Schwabe noticed that the sunspot number rose and fell in a cyclic fashion, with a period of about 11 years. Later workers confirmed this activity cycle, and the sunspot number remains today an important piece of information about the Sun.

The nature of sunspots was first investigated by American astronomer George Ellery Hale (1868 1938), who devoted his life to studying the Sun from the observatory he founded on Mt. Wilson near Los Angeles, California. Hale discovered that sunspots were cooler than the surrounding solar surface which is why they appear darkand that sunspots are associated with strong magnetic fields. Hale also discovered that the Suns magnetic field reverses itself with each 11-year cycle, so that there is a more fundamental 22-year magnetic activity cycle behind the sunspot cycle.

Since Hales time, solar research has developed along two great lines of investigation. First, a huge observational database has been created. The national solar observing facilities of the United States are located at Sacramento Peak just east of Alamogordo, New Mexico, and at Kitt Peak, 30 mi (48 km) west of Tucson, Arizona. In addition to sunspots, these observatories have monitored prominences and flareswhich are spectacular, eruptive events in the solar atmosphere, the solar magnetic field itself, the solar granulation, which is a result of the turbulent movement of the gas beneath the solar surface, and the total energy output of the Sun. Space-based satellites have studied the Sun in wavelength regimessuch as the ultraviolet and the x raynot accessible from the ground. The result of these investigations is a detailed set of observations about the phenomena that occur on the Sun.

The other line of investigation is the theoretical analysis of processes within the Sun and in its atmosphere. Scientists have developed models to explain what is observed; if a model fails to fit the observations, it must be discarded. The goal of this work is to explain why the various features seen on the Sun appear. Why is there an 11-year-long solar activity cycle? What do the forces producing granulation have to do with the nature of the solar magnetic field? Where does the magnetic field originate? These questions, and many others, are only partially answered.

A fruitful line of research toward answering these questions involves observing not just the Sun, but many other stars like the Sun. Scientists, for instance, would have a difficult time understanding what the human race was like by observing only one person. Similarly, it is hopeless to try to understand the complex nature of the stars by observing only one of them. Long-term observations of solar-like stars have been carried out at the Mount Wilson Observatory near Los Angeles and at Lowell Observatory in Flagstaff, Arizona. Understanding the so-called solar-stellar connection, derived from observations of other stars, may yield important clues about the processes at work in the Sun.

Two million years after humans earliest ancestors looked up and shielded their eyes from the brilliant, life-giving object in the sky, scientists still have only a rudimentary understanding of it.

A journey through the sun

The solar furnace

At the Suns core the temperature is 26,999,541°F (14,999,727°C). The matter here has a density of roughly 2.2 lb (1 kg) per cubic centimeterabout 150 times the density of water. It is compressed to this degree by the crushing weight of all the matter between it and the surfaceit is about 210,000 mi (350,000 km) from the core to the surface.

There are no atoms in the core. No atom (a nucleus of protons and neutrons, orbited by electrons) could exist in this inferno. There is nothing but a swirling sea of elementary particles. Scientists know from physics that the hotter a medium is, the faster its particles move. In the Suns core, the protons race around at blinding speeds, and because they are so tightly packed, they are constantly crashing into one another.

What is a proton? It is a hydrogen iona hydrogen atom that has had its sole electron stripped away. The Sun is made mostly of hydrogen. In the cool regions of its atmosphere the hydrogen exists as

atoms, with a single electron bound to the proton; in the core there are only the ions.

Four hydrogen nuclei smash together in a quick series of collisions, with catastrophic force. So violent are these collisions that the protons natural tendency to repel one anotherthey all have the same positive chargeis overcome. When the various interactions are over, a new particle has emerged: a helium nucleus containing two protons and two neutrons. The helium nucleus gets its share of battering by the other particles, but it is larger and tightly bound together, and even the maelstrom cannot disrupt it.

There is one more product of this fusion reaction. In the series of collisions leading to the formation of the helium nucleus, two particles called photons are produced. A photon is a bundle of electromagnetic radiation, also known as a ray of light. The photons race away from the Suns core at the incredible speed of 180,000 mi (300,000 km) per second, the speed of light.

Toward the surface

A proton does not travel to the surface in a straight line. It constantly hits other particles, bouncing off them in a random direction. Sometimes an atom absorbs its energy, only to re-emit it a fraction of a second later in a different direction. This is the so-called random walk, and it describes how a photon works from the Suns core.

Then, toward the surface, the temperature, pressure, and density of the gas drops. There is not as much weight compressing the gas, so it does not need to be at as high a pressure to support the material above it. Lower pressure means lower temperature and density.

Halfway from the Suns core to its surface is the zone of radiative energy transport, where uncountable trillions of photons flow away from the Suns core where they were produced. As they flow past, new photons, freshly created in the core, flow into it from below.

Into the convection zone

A little more than two-thirds of the way to the surface, the gas cools to less than 179,492°F (99,700°C). Instead of individual particles, atoms exist that are capable of absorbing the photons rather than simply scattering them in a different direction. Photons have difficulty flowing through this cool gas. As they are absorbed, new photons flow into the gas from below, heating it even more. The gas begins to overheat. As a result, energy transport is now more efficient if a huge bubble of hot gas forms and begins to rise toward the surface. This is called convection, which involves the Suns zone of convective energy transport.

A hot gas bubble rises into progressively cooler gas, releasing heat into smaller bubbles and reaching the very cool region just below the Suns surface. The bubbles release their pent-up heat. With their heat gone, they are now cooler than their surroundings, so they sink back into the Suns interior, to pick up more heat and begin the convective cycle anew.

In the atmosphere

It takes about 30,000 years for a photon to reach the Suns surface. Had the photon gone in a straight line, it would have reached the surface in just over one second, but 10 billion trillion interactions with matter in the Suns interior slowed it considerably.

At the surface is a thin (300 mi/500 km) layer of matter called the photosphere. The temperature here is 9,981°F (5,527°C), and for the first time, a photon of visual lightthat is, with a wavelength that places it in the visual portion of the spectrumhas a chance of escaping directly to outer space. The density of the gas is now so low that it is nearly a vacuum, thousands of times less dense than air, and so little matter is left that photons escape with no further interactions.

The photosphere is a seething region of hot, rising granules and cooler, sinking ones. In places there are great, dark spots, perhaps 6,200 mi (10,000 km) across, where the temperature is only 6,692°F (3,700°C) and where matter is constrained to flow along the intense and tangled lines of the strong magnetic fields that permeate the spots. (One phenomenon thought to contribute to the tangling of the solar magnetic field is the Suns rotation. The Suns equator rotates once every 26 days, its poles once every 36 days. This differential rotation contributes to twisting the magnetic fields and producing active features like sunspots.) The magnetic fields are invisible, but observations have revealed that they can arch high into the Suns atmosphere, forming loops. Hot gas becomes confined in these loops, forming spectacular prominences. Violent rearrangements or eruptions in twisted magnetic fields result in flares, which spew matter and intense radiation into space. Some of this radiation may interrupt radio communications on the Earth, while the particles will soon stream into the Earths atmosphere, causing aurorae.

Just above the photosphere, the temperature starts to climb, reaching 17,492°F (9,700°C) a few thousand miles above the photosphere. This is the chromosphere. Most of it is 10 million times less dense than air. The causes for the temperature rise are still not fully understood. One possibility is that mechanical energy from the convection zonethe energy associated with the motion of the gasis deposited into the Suns upper atmosphere, heating it. Because it is so thin and tenuous, the chromosphere is very faint, and under normal circumstances is invisible with the brilliant photosphere behind it. Scientists can see the chromosphere by photographing the Sun with special filters sensitive to light that originates in the chromosphere, or during an eclipse, when the Moon blocks the photosphere and the chromosphere appears as a glowing ring girdling the solar limb.

At 1,800 mi (3,000 km) above the photosphere, the temperature rises sharply35,541°F (19,727°C); then 179,541°F (99,727°C); then 899,541°F (499,727°C). A narrow transition region opens to the corona, an incredibly tenuous and hot3,599,541°F (1,999,727°C) region extending 3,000,000 mi (5,000,000 km) above the photosphere. The corona is also very faint, and can only be observed in visible light with the photosphere blocked, as it is during an eclipse. Because the corona is so hot, it is also spectacular in x-ray photographs, which can be obtained only from space-based observatories.

The solar wind

The end of the corona marks the last of the Suns strong magnetic field regions. The photon races into empty space.

There are also swarms of particles. There are only a few per cubic centimeteran almost perfect vacuum. They are all part of the solar wind, a continuous stream of matter flowing away from the Sun. Slowly, the Sun is losing material to space. The rate of this loss is very small, so it will not seriously affect the Suns evolution. (Some stars, however, have powerful winds that can carry off a substantial fraction of their mass.) The solar wind permeates the entire solar system, and beyond.

A small blue planet

About eight minutes after a photon leaves the Suns photosphere, it reaches the Earth. Along with countless billions of other photons, it streams through the Earths atmosphere. The photon, a product of a hydrogen fusion reaction 30,000 years ago, has finished its trip. Obviously the Sun has a profound impact on Earth, but recent research suggests the connections may run deeper than initially thought.

The link may lie in the solar activity cycle, which is the periodic variation in active features such as sunspots, prominences, and flares, in the Suns atmosphere and on its visible surface. The cause of the activity cycle is not well understood, but astronomers generally agree that the Suns ifferential rotation, combined with the turbulent motions in its convection

KEY TERMS

Chromosphere The narrow middle layer of the Suns atmosphere. It is about 17,492°F (9,700°C) and is very faint relative to the photosphere.

Convection zone The outermost third of the solar interior. Here heat is transported to the surface in giant convective bubbles of gas, which rise to the surface, release their heat, and then sink back into the interior to pick up more heat.

Core The central region of the Sun, where thermonuclear fusion reactions take place.

Corona The highest and hottest layer of the solar atmosphere. Matter in the corona may have a temperature of 3,599,541°F (1,999,727°C) and may be several million miles above the photosphere.

Photosphere The lowest layer of the solar atmosphere, where most of the visible light is emitted. Because this is the layer humans see in white light photographs, it is often called the solar surface, even though it is a very thin gas.

Prominence A large region of glowing gas suspended in magnetic fields, often arching far above the photosphere. Some prominences are quiescent, remaining for days, while others are eruptive, and dissipate violently.

Radiative zone The central two-thirds of the solar interior. Here energy is transported by the flow of photons, or light waves, through the matter.

zone, create a magnetic dynamo that results in a perpetual tangling and rearrangement of the Suns magnetic field. When magnetic field lines, which normally lie below the photosphere, become tangled and burst into the Suns atmosphere, active features such as sunspots and prominences invariably form. When the magnetic field becomes tangled to a critical level, it rearranges and simplifies its configuration, and the amount of solar activity decreases correspondingly. The sunspot cycle typically has a length of about 11 years, but there is compelling circumstantial evidence that variations in the length of the solar activity cycle are closely related to changes in the global temperature, with shorter solar cycles corresponding to warmer temperatures on the Earth.

And, in the end, the Sun will have its final and greatest impact on the Earth. What of the core, which the photon left a million years ago? If scientists are correct in their predictions, around seven billion years from now, the seemingly countless hydrogen nuclei will all have been converted into helium ashthe Suns fuel will be gone. To stave off destruction by the inexorable force of gravity, the Suns core will contract and heat to the point that the helium will ignite. In the process, the Sun will expand into a red giant star, swallowing the innermost planet, Mercury, and turning the Earth into a charred wasteland. However, the helium is the last fuel reserve the Sun will be able to use, and it will eject its outer layers, leaving behind only its collapsed core, a small, dying white dwarf.

As of May 2006, the Solar and Heliospheric Observatory (SOHO) had been studying the Sun for ten years. As a joint venture of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), SOHO studies the outer layer of the Sun (the chromosphere transition region and the corona), making measurements of the solar wind, and investigating the interior structure of the Sun. The SOHO mission has dramatically increased scientific knowledge of the Sun, the deep within its interior to the edge of the solar wind.

See also Seasons; Solar flare; Star formation; Stellar evolution.

Resources

BOOKS

Arny, Thomas. Explorations: An Introduction to Astronomy. Boston, MA: McGraw-Hill, 2006.

Bhatnagar, Aravind. Fundamentals of Solar Astronomy. Hackensack, NJ: World Scientific, 2005.

Chaisson, Eric. Astronomy: A Beginners Guide to the Universe. Upper Saddle River, NJ: Pearson/Prentice Hall, 2004.

Hill, Steele, and Michael Carlowicz. The Sun. New York: Abrams, 2006.

Mendillo, Michael, Andrew Nagy, and J.H. Waite, eds. Atmospheres in the Solar System: Comparative Aeronomy. Washington, DC: American Geophysical Union, 2002.

Jeffrey C. Hall

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Sun

Sun

Theme Overview

The largest object in the sky, the sun is the source of light, heat, and life. It can also be a symbol of destructive power. Since earliest times, people in all parts of the world have observed the position of the sun and its rising and setting throughout the year. Many cultures have created solar calendars to use for planting crops and timing religious festivals. They have also given the sun a major place in their mythologies, often as a deity, or god.

Major Myths

Some solar myths explain the sun's daily movement across the sky from east to west and its disappearance at night. Such stories often take the form of a journey, with the sun deity traveling across the heavens in a chariot or boat. Helios (pronounced HEE-lee-ohs), a Greek solar deity later identified with Apollo , was a charioteer who drove his fiery vehicle through heaven by day. At night he floated back across the ocean in a golden bowl, only to mount his chariot again the next morning. The Navajo people of the American Southwest portray their sun god as a worker named Johonaa'ei, or sun bearer. Every day Johonaa'ei laboriously hauls the sun across the sky on his back. At night, he hangs the sun from a peg in the wall and rests.

The Egyptian sun god Ra made a similar circuit. Each day he traveled across the sky in his sun boat, and at night he passed through the underworld , or land of the dead, greeting the dead and facing many dangers. Ra's daily cycle was more than a journey, though—it was a daily rebirth. Dawn saw the newborn sun god rise in the sky. During the morning he was a child, at noon he was mature, and by sunset he was an old man ready for death. Each sunrise was a celebration of the god's return, a victory of life over the forces of death and darkness.

In some solar myths the sun is paired with the moon. The two may be husband and wife, brother and sister, or two brothers. In the mythology of many Native Americans, the sun god and moon god are sister and brother who also become forbidden lovers. The moon god's face is smeared with ash from the sun's fires, which accounts for the dark patches on the moon's surface. In some accounts, the moon flees in shame when he learns that his lover is also his sister. This is why the moon leaves the sky when the sun comes near.

Too Many Suns

If one sun is good, are ten suns ten times better? Not according to the Chinese myth of Yi and the ten suns. Yi, a famous soldier, was an archer of great skill. At that time, ten suns lived in the Fu Sang tree beyond the eastern edge of the world. Normally the suns took turns lighting the earth, one sun at a time. The suns grew rebellious, and one day all ten of them rose into the sky at the same time. The extra light and heat pleased the people below—until their crops shriveled and their rivers began to dry up. The Lord of Heaven sent Yi, the divine archer, to handle the problem. Yi shot nine of the suns out of the sky.

Many cultures have myths of monsters or evil spirits that steal or devour the sun, or stories of the sun falling from the heavens or withdrawing its light for a time. Some of these myths may explain eclipses, times when the earth's shadow temporarily blots out the sun or moon. A solar eclipse creates a period of eerie near-darkness in the middle of the day—an event that would surely cry out for a reassuring explanation. A well-known myth about the Japanese sun goddess Amaterasu (pronounced ah-mah-te-RAH-soo), tells how she became so angry with her brother, who was misbehaving, that she retreated into a cave. The goddess's withdrawal deprived the world of light and warmth. Finally, the other gods tricked her into emerging.

According to a traditional myth from the Hindu Kush mountains of Afghanistan, the giant Espereg-era once stole the sun and the moon. The hero god Mandi disguised himself as a child and tricked the giant's mother into adopting him. After a time with the giants , Mandi rescued the sun and moon and rode off with them on a magical horse. The supreme god then hurled them into the sky to shine on the world.

The Sun in Context

The mythologies of many cultures have included a sun deity, usually a god but occasionally a goddess. Some myths reflect the sun's vital role in supporting life: solar deities are often creators who bring people into existence. Native Americans from the Pacific Coast, for example, tell how the sun god Kodoyanpe and the trickster Coyote together created the world and set about making people to live in it.

Solar deities have also been associated with fertility of people and the earth. The Hittites of ancient Turkey worshiped Arinna, an important goddess of both the sun and fertility. In traditional myths from Uganda in Central Africa, the creator god Ruhanga, the sun god Kazooba, and the giver of life Rugaba are all the same deity.

In some mythologies, sun gods have healing powers. Shamash (pronounced shah-MAHSH), the solar god of the Babylonian people of the ancient Near East, was known as “the sun with healing in his wings.” Ancient Celtic peoples had Belenus (pronounced BEHL-eh-nuhs), the god of sunlight: besides driving away the predawn mists and fogs each day, Belenus could melt away disease from the sick. When the Romans conquered the Celts, they identified Belenus with their own sun god, Apollo (pronounced uh-POL-oh), who was also a god of healing.

As the most important and splendid deities of their pantheons, some solar deities have been associated with earthly rulers, the most powerful people in society. The Incas of Peru in South America regarded the sun god Inti (pronounced IN-tee), their chief deity, as the ancestor of the Inca royal family. According to Japanese tradition, the country's imperial family is descended from Amaterasu, the sun goddess.

The Sun in Art, Literature, and Everyday Life

The sun is perhaps the most universally depicted object in all of mythological art. It appears in ancient Egyptian and Persian art as well as in some of the first examples of Nordic art. Some of the most enduring depictions of the sun in mythological art include the ancient Egyptian god Ra, usually pictured with the head of a falcon crowned with a sun disk; the Greek gods Helios and Apollo, often shown pulling the sun through the sky with a chariot; and the Japanese goddess Amaterasu, shown exiting the cave where she hides to bring sunlight back into the world. In modern times, the image of the sun is still used in advertising and art to symbolize life, purity, health, and happiness.

Read, Write, Think, Discuss

Sun deities are often thought of as male figures. However, many sun deities in cultures around the world are female, such as Amaterasu. Using your library, the Internet, or other available resources, research various cultures with either male or female sun deities. Why do you think some cultures view the sun as a male figure, while others view it as a female figure? What do you think this might indicate about those cultures?

SEE ALSO Amaterasu; Apollo; Aten; Lug; Ra; Shamash

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Sun

Sun

The Sun is the star at the center of our solar system . It has a diameter of about 420,000 mi (700,000 km) and a surface temperature of 9,981°F (5,527°C). Its visible "surface" is actually a thin gas, as is the rest of its atmosphere and interior.

The Sun shines as a result of thermonuclear fusion reactions in its core, and the energy produced by these reactions heats the gas in the Sun's interior sufficiently to prevent the weight of its own matter from crushing it. This energy also is the source of heat and life on Earth , and small variations in the Sun's energy output, or even in the features present in its atmosphere, may be sufficient to profoundly affect terrestrial climate. Although the Sun is by far the nearest star, the processes causing solar variability are still poorly understood and continue to challenge astronomers.


A brief history of solar observations

The Sun is about 90 million mi (150 million km) away from Earth. It is modest by stellar standards, although it is over 100 times larger than the earth and over 300,000 times more massive. Although it consumes more than half a billion tons of its nuclear fuel each second, it has been shining continuously for five billion years, and it will continue to shine for another five billion.

To the ancient Egyptians the Sun was a god, for anyone who felt its warmth and watched the renewal of crops it brought in the spring realized it was a bringer of life. Greek mythology recounts the tale of Icarus, who died in a brazen attempt to fly too close to the Sun.

Ancient dogma held that the Sun orbited Earth. It was not until 1543 that Nikolaus Copernicus (1473-1543) published the heliocentric theory of the Universe, in which the Sun lay at the center and Earth was relegated to a circular orbit around it. Copernicus refused to have this magnificent work published until near his death. This was a wise decision, since earlier publication would have resulted in his equally earlier death at the hand of Church authorities who regarded his work as heresy.

Around 1610, the newly invented telescope was trained on the Sun. The early solar observers, including Galileo (1564-1642), noticed that the surface of the Sun had dark spots on it. Not only that, the spots moved across the solar surface, leading Galileo to conclude that the Sun rotated. This sent further shock waves through the religious world. The poor cardinals had hardly recovered from Copernicus's heresy, and now along came Galileo telling them that the backup embodiment of celestial perfection, the Sun, had ugly blemishes on its surface. Galileo got into serious trouble with the Church for this and other statements he made, and it would be 380 years before Pope John Paul II exonerated him.

In the nineteenth century an amateur German astronomer named Heinrich Schwabe (1789-1875) did some of the first scientific analysis of solar data. Observers had kept records over the years of the number of sunspots visible, and Schwabe noticed that the sunspot number rose and fell in a cyclic fashion, with a period of about 11 years. Later workers confirmed this activity cycle, and the sunspot number remains today an important piece of information about our star.

The nature of sunspots was first investigated by George Ellery Hale (1868-1938), who devoted his life to studying the Sun from the observatory he founded on Mt. Wilson near Los Angeles. Hale discovered that sunspots were cooler than the surrounding solar surface—which is why they appear dark—and that sunspots are associated with strong magnetic fields. Hale also discovered that the sun's magnetic field reverses itself with each 11-year cycle, so that there is a more fundamental 22-year magnetic activity cycle behind the sunspot cycle.

Since Hale's time, solar research has developed along two great lines of investigation. First, a huge observational database has been created. The national solar observing facilities of the United States are located at Sacramento Peak just east of Alamogordo, New Mexico, and at Kitt Peak, 30 mi (48 km) west of Tucson, Arizona. In addition to sunspots, these observatories have monitored prominences and flares, which are spectacular, eruptive events in the solar atmosphere, the solar magnetic field itself, the solar granulation, which is a result of the turbulent movement of the gas beneath the solar surface, and the total energy output of the Sun. Space-based satellites have studied the Sun in wavelength regimes, such as the ultraviolet and the x ray, not accessible from the ground. The result of these investigations is a detailed set of observations about the phenomena that occur on our star.

The other line of investigation is the theoretical analysis of processes within the Sun and in its atmosphere. Scientists have developed models to explain what is observed; if a model fails to fit the observations, it must be discarded. The goal of this work is to explain why the various features seen on the Sun appear. Why is there an 11-year-long solar activity cycle ? What do the forces producing granulation have to do with the nature of the solar magnetic field? Where does the magnetic field originate? These questions, and many others, are only partially answered.

A fruitful line of research toward answering these questions involves observing not just the sun, but many other stars like the Sun. You would have a difficult time understanding what the human race was like by observing only one person; similarly, it is hopeless to try to understand the complex nature of the stars by observing only one of them. Long-term observations of solar-like stars have been carried out at the Mount Wilson Observatory near Los Angeles and at Lowell Observatory in Flagstaff, Arizona. Understanding the so-called "solar-stellar connection," derived from observations of other stars, may yield important clues about the processes at work in our own star.

Two million years after our earliest ancestors looked up and shielded their eyes from the brilliant, life-giving object in the sky, we still have only a rudimentary understanding of it.


A journey through the Sun

The solar furnace

At the sun's core, the temperature is 26,999,541°F (14,999,727°C). The matter here has a density of roughly 2.2 lb (1 kg) per cubic centimeter—about 150 times the density of water . It is compressed to this degree by the crushing weight of all the matter between it and the surface—it is about 210,000 mi (350,000 km)—to the surface.

There are no atoms in the core. No atom (a nucleus of protons and neutrons, orbited by electrons) could exist in this inferno. There is nothing but a swirling sea of particles. We know from physics that the hotter a medium is, the faster its particles move. In the Sun's core the protons race around at blinding speeds, and because they are so tightly packed, they are constantly crashing into one another.

What is a proton ? It is a hydrogen ion-a hydrogen atom that has had its sole electron stripped away. The sun is made mostly of hydrogen. In the cool regions of its atmosphere the hydrogen exists as atoms, with a single electron bound to the proton; in the core there are only the ions.

Four hydrogen nuclei smash together in a quick series of collisions, with catastrophic force . So violent are these collisions that the protons' natural tendency to repel one another—they all have the same positive charge—is overcome. When the various interactions are over, a new particle has emerged: a helium nucleus containing two protons and two neutrons. The helium nucleus gets its share of battering by the other particles, but it is larger and tightly bound together, and even the maelstrom cannot disrupt it.

There is one more product of this fusion reaction. In the series of collisions leading to the formation of the helium nucleus, two particles called photons are produced. A photon is a bundle of electromagnetic radiation , also known as a ray of light . The photons race away from the Sun's core at the incredible speed of 180,000 mi (300,000 km) per second, the speed of light.


Toward the surface

Photons do not travel to the surface in a straght line. They constantly hit other particles, bouncing off them in a random direction. Sometimes an atom absorbs its energy, only to re-emit it a fraction of a second later in a different direction. This is the so-called random walk, and it describes how photons work out from the Sun's core.

Then toward the surface, the temperature, pressure, and density of the gas drop. There is not as much weight compressing the gas, so it does not need to be at as high a pressure to support the material above it. Lower pressure means lower temperature and density.

Halfway from the Sun's core to its surface, we are in the zone of radiative energy transport, where uncountable trillions of photons flow away from the Sun's core where they were produced. As they flow past, new photons, freshly created in the core, flow into it from below.


Into the convection zone

A little more than two-thirds of the way to the surface, gas cools to 179,492°F; (99,700°C). Instead of individual particles, atoms exist, which are capable of absorbing the photons rather than simply scattering them in a different direction. Photons have difficulty flowing through this cool gas. As they get absorbed, new photons flow into the gas from below, heating it even more. The gas begins to overheat. As a result, energy transport is now more efficient if a huge bubble of hot gas forms and begins to rise toward the surface. This is called convection, and we are now in the Sun's zone of convective energy transport.

A hot gas bubble rises into progressively cooler gas, releasing heat into smaller bubbles reaching the very cool region just below the Sun's surface. The bubbles release their pent-up heat. With their heat gone, they are now cooler than their surroundings, so they sink back into the Sun's interior, to pick up more heat and begin the convective cycle anew.


In the atmosphere

It takes about 30,000 years for a photon to reach the Sun's surface. Had the photon gone in a straight line, it would have reached the surface in just over one second, but 10 billion trillion interactions with matter in the Sun's interior slowed it considerably.

At the surface is a thin (300 mi/500 km) layer of matter called the photosphere. The temperature here is 9,981°F; (5,527°C), and for the first time, a photon of visual light—that is, with a wavelength that places it in the visual portion of the spectrum—has a chance of escaping directly to outer space. The density of the gas is now so low that it is nearly a vacuum , thousands of times less dense than air, and so little matter is left that photons escape with no further interactions.

The photosphere is a seething region of hot, rising granules and cooler, sinking ones. In places there are great, dark spots, perhaps 6,200 mi (10,000 km) across, where the temperature is only 6,692°F; (3,700°C) and where matter is constrained to flow along the intense and tangled lines of the strong magnetic fields that permeate the spots. (One phenomenon thought to contribute to the tangling of the solar magnetic field is the Sun's rotation . The Sun's equator rotates once every 26 days, its poles once every 36 days. This differential rotation contributes to twisting the magnetic fields and producing active features like sunspots.) The magnetic fields are invisible, but observations have revealed that they can arch high into the Sun's atmosphere, forming loops. Hot gas becomes confined in these loops, forming spectacular prominences. Violent rearrangements or eruptions in twisted magnetic fields result in flares, which spew matter and intense radiation into space. Some of this radiation may interrupt radio communications on Earth, while the particles will soon stream into Earth's atmosphere, causing aurorae.

Just above the photosphere, the temperature starts to climb, reaching 17,492°F; (9,700°C) a few thousand miles above the photosphere. This is the chromosphere. Most of it is ten million times less dense than air. The causes for the temperature rise are still not fully understood. One possibility is that mechanical energy from the convection zone—the energy associated with the motion of the gas—is deposited into the Sun's upper atmosphere, heating it. Because it is so thin and tenuous, the chromosphere is very faint, and under normal circumstances is invisible with the brilliant photosphere behind it. We can see the chromosphere by photographing the Sun with special filters sensitive to light that originates in the chromosphere, or during an eclipse, when the Moon blocks the photosphere and the chromosphere appears as a glowing ring girdling the solar limb.

Now 1,800 mi (3,000 km) above the photosphere, the temperature rises sharply—1,935,541°F; (19,727°C), then 179,541°F; (99,727°C), then 899,541°F; (499,727°C). A narrow transition region opens to the corona, an incredibly tenuous and hot—3,599,541°F; (1,999,727°C)—region extending 3,000,000 mi (5,000,000 km) above the photosphere. The corona is also very faint, and can only be observed in visible light with the photosphere blocked, as it is during an eclipse. Because the corona is so hot, it is also spectacular in x ray photographs, which can be obtained only from space-based observatories.

The solar wind

The end of the corona marks the last of the Sun's strong magnetic field regions. photons race into empty space.

There are also swarms of particles. There are only a few per cubic centimeter—an almost perfect vacuum. They are all part of the solar wind , a continuous stream of matter flowing away from the sun. Slowly, the Sun is losing material to space. The rate of this loss is very small, so it will not seriously affect the Sun's evolution . (Some stars, however, have powerful winds that can carry off a substantial fraction of their mass.) The solar wind permeates the entire solar system, and beyond.


A small blue planet

Eight minutes after a photon leaves the Sun's photosphere, it reaches Earth. Along with countless billions of other photons, it streams through Earth's atmosphere. The photon, a product of a hydrogen fusion reaction 30,000 years ago, has finished its trip. Obviously the Sun has a profound impact on doings here on Earth, but recent research suggests the connections may run deeper than initially thought.

The link may lie in the solar activity cycle, which is the periodic variation in active features such as sunspots, prominences, and flares, in the Sun's atmosphere and on its visible surface. The cause of the activity cycle is not well understood, but astronomers generally agree that the Sun's differential rotation, combined with the turbulent motions in its convection zone, create a magnetic dynamo that results in a perpetual tangling and rearrangement of the Sun's magnetic field. When magnetic field lines, which normally lie below the photosphere, become tangled and burst into the Sun's atmosphere, active features such as sunspots and prominences invariably form. When the magnetic field becomes tangled to a critical level, it rearranges and simplifies its configuration, and the amount of solar activity decreases correspondingly. The sunspot cycle typically has a length of about 11 years, but there is compelling circumstantial evidence that variations in the length of the solar activity cycle are closely related to changes in the global temperature, with shorter solar cycles corresponding to warmer temperatures on Earth.

And in the end, the sun will have its final and greatest impact on Earth. What of the core, which our photon left a million years ago? Five billion years from now, the seemingly countless hydrogen nuclei will all have been converted into helium "ash"—the Sun's fuel will be gone. To stave off destruction by the inexorable force of gravity, the sun's core will contract and heat to the point that the helium will ignite. In the process, the sun will expand into a red giant star , swallowing the innermost planet, Mercury, and turning Earth into a charred wasteland. But the helium is the last fuel reserve the sun will be able to use, and it will eject its outer layers, leaving behind only its collapsed core, a small, dying white dwarf.

See also Seasons; Solar flare; Star formation; Stellar evolution.

Resources

books

Seeds, M.A. Horizons, Discovering the Universe. New York. Wiley, 1991.


periodicals

Giampapa, Mark S. "The Solar-Stellar Connection." Sky &Telescope (August 1987): 142.

Pasachoff, J. "The Sun: A Star Close Up," Mercury (May/June 1991): 66.

Jeffrey C. Hall

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chromosphere

—The narrow middle layer of the Sun's atmosphere. It is about 17,492°F; (9,700°C) and is very faint relative to the photosphere.

Convection zone

—The outermost third of the solar interior. Here heat is transported to the surface in giant convective bubbles of gas, which rise to the surface, release their heat, and then sink back into the interior to pick up more heat.

Core

—The central region of the Sun, where thermonuclear fusion reactions take place.

Corona

—The highest and hottest layer of the solar atmosphere. Matter in the corona may have a temperature of 3,599,541°F (1,999,727°C) and may be several million miles above the photosphere.

Photosphere

—The lowest layer of the solar atmosphere, where most of the visible light is emitted. Because this is the layer we see in white light photographs, it is often called the solar "surface," even though it is a very thin gas.

Prominence

—A large region of glowing gas suspended in magnetic fields, often arching far above the photosphere. Some prominences are quiescent, remaining for days, while others are eruptive, and dissipate violently.

Radiative zone

—The central two-thirds of the solar interior. Here energy is transported by the flow of photons, or light waves, through the matter.

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Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.