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photosphere
photosphere luminous, apparently opaque layer of gases that forms the visible surface of the sun or any other star. The photosphere lies between the dense interior gases and the more attenuated gases of the chromosphere . The incandescent gases of the photosphere, estimated to be at temperatures near 6,000°K, are so much brighter than the other layers of the sun that they seem to form a surface. These gases are in a constant state of agitation due to convection currents that reach down to 150,000 mi (241,000 km) below the photosphere. Differences in the density of the gases result in a grainy appearance of the photosphere; the small bright patches, or granules, are several hundred miles in diameter and are constantly shifting. Another feature of the photosphere, observed only near the sun's edge, is the appearance near sunspots of bright, veinlike regions known as faculae. |
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"photosphere." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "photosphere." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1E1-photosph.html "photosphere." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-photosph.html |
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photosphere
photosphere The visible surface of a star, from which most of its energy is emitted in the form of visible and infrared radiation. The name means ‘light sphere’. The Sun's photosphere is a thin layer about 500 km deep. Its temperature decreases steadily from about 6400 K at its base to 4400 K at the temperature minimum, where it merges with the chromosphere above. This drop in temperature with height causes limb darkening. The photosphere has a rice-grain texture called granulation, caused by rising convection cells of hot gas. Other photospheric features include sunspots, faculae, and filigree structures, all associated with strong magnetic fields. Almost all the features of the Sun's visible-light spectrum originate in the photosphere, including the dark Fraunhofer lines.
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"photosphere." A Dictionary of Astronomy. 1997. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "photosphere." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O80-photosphere.html "photosphere." A Dictionary of Astronomy. 1997. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-photosphere.html |
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photosphere
photosphere Visible surface of the Sun. It is a layer of highly luminous gas c.500km (300mi) thick and with a temperature of c.6000K, falling to 4000K at its upper level. The photosphere is the source of the Sun's visible spectrum. The lower, hotter gases produce the continuous emission spectrum, while the higher, cooler gases absorb certain wavelengths. Sunspots and other visible features of the Sun are situated in the photosphere.
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"photosphere." World Encyclopedia. 2005. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "photosphere." World Encyclopedia. 2005. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O142-photosphere.html "photosphere." World Encyclopedia. 2005. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-photosphere.html |
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photosphere
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AILSA ALLABY and MICHAEL ALLABY. "photosphere." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "photosphere." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O13-photosphere.html AILSA ALLABY and MICHAEL ALLABY. "photosphere." A Dictionary of Earth Sciences. 1999. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-photosphere.html |
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