Black hole

A black hole, among the most mysterious elements in the universe, is all that remains of a massive star that has used up its nuclear fuel. Lacking energy to combat the force of its own gravity, the star compresses or shrinks in size to a single point, called a singularity. At this point, pressure and density are infinite. Any object or even light that gets too close to a black hole is pulled in, stretched to infinity, and trapped forever. Black holes, so named by American physicist John Wheeler in 1969, are impossible to see, but may account for 90 percent of the content of the universe.

English geologist John Michell and French astronomer Pierre-Simon Laplace first developed the idea of black holes in the eighteenth century. They theorized that if a celestial body were large enough and dense enough, it would exhibit so much gravity that nothing could escape its pull.

This idea can be explained by looking at the effects of gravity on known objects. To break free of Earth's gravity, a spaceship has to travel at a speed of at least 7 miles (11 kilometers) per second. To escape a larger planet like Jupiter, it would have to travel at 37 miles (60 kilometers) per second. And to escape the Sun, it would have to travel at 380 miles (611 kilometers) per second. A large and dense enough object could require the spaceship to go faster than the speed of light, 186,000 miles (299,000 kilometers) per second. However, since nothing can travel faster than the speed of light, nothing would be able to escape the gravity of such an object. Black holes, indeed, are such objects.

Black hole formation

Once a star's nuclear fuel is spent, it will collapse. Without the force of nuclear fusion pushing outward from its core to balance its immense gravity, a star will fall into itself. Average-sized stars, like the Sun, shrink to become white dwarfs (small, extremely dense stars having low brightness) about the size of Earth. Stars up to three times the mass of the Sun explode to produce a supernova. Any remaining matter of such stars ends up as densely packed neutron stars or pulsars (rapidly rotating stars that emit varying radio waves at precise intervals). Stars more than three times the mass of the Sun explode in a supernova and then, in theory, collapse to form a black hole.

When a giant star collapses, its remaining mass becomes so concentrated that it shrinks to an indefinitely small size and its gravity becomes completely overpowering. According to German-born American physicist Albert Einstein's (1879–1955) general theory of relativity, space becomes curved near objects or matter; the more concentrated or dense that matter is, the more space is curved around it. When a black hole forms, space curves so completely around it that only a small opening to the rest of normal space remains. The surface of this opening is called the event horizon, a theorized point of no-return. Any matter that crosses the event horizon is drawn in by the black hole's gravity and cannot escape, vanishing across the boundary like water down a drain.

Black hole evidence

Black holes cannot be seen because matter, light, and other forms of energy do not escape from them. They can possibly be detected, however, by their effect on visible objects around them. Scientists believe that as gaseous matter swirls in a whirlpool before plunging into a black hole, that heated matter emits fluctuating X rays. Discovery of such a condition in space, therefore, may indicate the existence of a black hole near the source of those X rays.

In 1971, an X-ray telescope aboard the satellite Uhuru detected the first serious black hole candidate in our galaxy, the Milky Way. A black hole is believed to be the companion star in a binary star called Cygnus X-1 (a binary star is a pair of stars in a single system that orbit each other, bound together by their mutual gravities). Cygnus X-1 is emitting intense amounts of X rays, possibly as a result of the unseen companion pulling in stellar material from the other star.

Words to Know

Binary star: Pair of stars in a single system that orbit each other, bound together by their mutual gravities.

General theory of relativity: A theory of gravity put forth by Albert Einstein in 1916 that describes gravity as a distortion or curvature of space-time caused by the presence of matter.

Light-year: Distance light travels in one solar year, roughly 5.9 trillion miles (9.5 trillion kilometers).

Pulsars: Rapidly rotating stars that emit varying radio waves at precise intervals; also known as neutron stars because much of the matter within has been compressed into neutrons.

White dwarf: Average-sized star that has collapsed to about the size of Earth and has extreme density and low brightness.

In the 1990s, the Hubble Space Telescope provided scientists with evidence that black holes probably exist in nearly all galaxies and in interstellar space between galaxies. The biggest black holes are those at the center of galaxies. In the giant galaxy M87, located in the constellation Virgo, swirling gases around a suspected massive black hole stretch a distance of 500 light-years, or 2,950 trillion miles (4,750 trillion kilometers).

In early 2001, scientists announced that data from the Chandra X-Ray Observatory and the Hubble Space Telescope provided the best direct evidence for the existence of the theorized event horizons. The two Earth-orbiting telescopes both surveyed matter surrounding suspected black holes that eventually disappeared from view. The Chandra telescope observed X-ray emissions that disappeared around six candidate black holes, while the Hubble telescope observed pulses of ultraviolet light from clumps of hot gas as they faded and then disappeared around Cygnus X-1.

Types of black holes

Until very recently, scientists believed there were only two types of black holes. The first kind, stellar black holes, form from the remains

of collapsed stars that have, at most, 10 times the mass of the Sun. The second type, supermassive black holes, are believed to have been formed when the universe was very young. It is also believed they are the most common, existing at the core of every galaxy in the universe. These gigantic black holes have masses up to that of a billion Suns. In 2000, astrophysicists from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, announced they had convincing evidence for a new class of black hole: midsize black holes. Using observations from the Chandra X-Ray Observatory of a galaxy about 12 million light-years from Earth, the scientists theorized the existence of a black hole in that galaxy with a mass of at least 500 Suns. How a midsize black hole like this forms, however, remains a puzzle for scientists.

[See also Relativity, theory of; Star; Supernova ]

black hole in astronomy, celestial object of such extremely intense gravity that it attracts everything near it and in some instances prevents everything, including light, from escaping. The term was first used in reference to a star in the last phases of gravitational collapse (the final stage in the life history of certain stars; see stellar evolution ) by the American physicist John A. Wheeler .

Gravitational collapse begins when a star has depleted its steady sources of nuclear energy and can no longer produce the expansive force, a result of normal gas pressure , that supports the star against the compressive force of its own gravitation . As the star shrinks in size (and increases in density), it may assume one of several forms depending upon its mass. A less massive star may become a white dwarf , while a more massive one would become a supernova . If the mass is less than three times that of the sun, it will then form a neutron star . However, if the final mass of the remaining stellar core is more than three solar masses, as shown by the American physicists J. Robert Oppenheimer and Hartland S. Snyder in 1939, nothing remains to prevent the star from collapsing without limit to an indefinitely small size and infinitely large density, a point called the "singularity."

At the point of singularity the effects of Einstein's general theory of relativity become paramount. According to this theory, space becomes curved in the vicinity of matter; the greater the concentration of matter, the greater the curvature. When the star (or supernova remnant) shrinks below a certain size determined by its mass, the extreme curvature of space seals off contact with the outside world. The place beyond which no radiation can escape is called the event horizon, and its radius is called the Schwarzschild radius after the German astronomer Karl Schwarzschild, who in 1916 postulated the existence of collapsed celestial objects that emit no radiation. For a star with a mass equal to that of the sun, this limit is a radius of only 1.86 mi (3.0 km). Even light cannot escape a black hole, but is turned back by the enormous pull of gravitation.

It is now believed that the origin of some black holes is nonstellar. Some astrophysicists suggest that immense volumes of interstellar matter can collect and collapse into supermassive black holes, such as are found at the center of some galaxies. The British physicist Stephen Hawking has postulated still another kind of nonstellar black hole. Called a primordial, or mini, black hole, it would have been created during the "big bang," in which the universe was created (see cosmology ). Unlike stellar black holes, primordial black holes create and emit elementary particles , called Hawking radiation, until they exhaust their energy and expire. It has also been suggested that the formation of black holes may be associated with intense gamma ray bursts. Beginning with a giant star collapsing on itself or the collision of two neutron stars, waves of radiation and subatomic particles are propelled outward from the nascent black hole and collide with one another, releasing the gamma radiation . Also released is longer-lasting electromagnetic radiation in the form of X rays , radio waves, and visible wavelengths that can be used to pinpoint the location of the disturbance.

Because light and other forms of energy and matter are permanently trapped inside a black hole, it can never be observed directly. However, a black hole can be detected by the effect of its gravitational field on nearby objects (e.g., if it is orbited by a visible star), during the collapse while it was forming, or by the X rays and radio frequency signals emitted by rapidly swirling matter being pulled into the black hole. The first discovery (1971) of a possible black hole was Cygnus X-1, an X-ray source in the constellation Cygnus. In 1994 astronomers employing the Hubble Space Telescope announced that they had found conclusive evidence of a supermassive black hole in the M87 galaxy in the constellation Virgo. Since then others have been found, and in 2011 astronomers announnced the discovery of one, in NGC 4889 in the constellation Coma, whose mass may be as great as 21 billion times that of the sun. The first evidence (2002) of a binary black hole, two supermassive black holes circling one another, was detected in images from the orbiting Chandra X-ray Observatory. Located in the galaxy NGC6240, the pair are 3,000 light years apart, travel around each other at a speed of about 22,000 mph (35,415 km/hr), and have the mass of 100 million suns each. As the distance between them shrinks over 100 million years, the circling speed will increase until it approaches the speed of light, about 671 million mph (1080 million km/hr). The black holes will then collide spectacularly, spewing radiation and gravitational waves across the universe. The Chandra observatory has also discovered that massive black holes were associated with galaxies that existed 13 billion years ago.

Bibliography: See S. W. Hawking, Black Holes and Baby Universes and Other Essays (1994); P. Strathern, The Big Idea: Hawking and Black Holes (1998); J. A. Wheeler, Geons, Black Holes, and Quantum Foam: A Life in Physics (1998); H. Falcke and F. W. Hehl, The Galactic Black Hole: Studies in High Energy Physics, Cosmology and Gravitation (2002).

BLACK HOLE

Frances Tustin introduced the idea of black holes in her Autistic Barriers in Neurotic Patients (1986). The term was chosen by analogy with ideas in modern astrophysics, which has discovered zones of extraordinary density in the universe that are probably related to the condensation and fusion of several stars. Once formed, such hyperdense zones are thought to exert a sort of attraction upon other stars, which are thus at risk of plunging into the core of these vast concentrations of matter, which swallow them up and strip them of all individuality. It is not hard to see how the metaphor of a "black hole of the psyche" can help explain, or at least help us picture what happens at the core of the psyche of autistic children.

Indeed Tustin had already elaborated on a notion first proposed by Sydney Klein (1980), that of "autistic islands." And, most significantly, in her first book, Autism and Childhood Psychosis (1972), she had painstakingly recounted the case of John, who had described to her, on emerging from autism, what he himself called "the black hole w/the mechant piquant." What John was striving to verbalize in this way was all the pain and suffering he had felt on the occasion of far too brutal and premature a separation between the breast and the nipple, this at a time when nipple and mouth are inextricably conjoined (as described, albeit in a different way, by Piera Aulagnier, with her "complementary zone-object"). Naturally it is less a physical separation that is involved here than a mental one—or even, to be quite precise, the inscription in the psyche of the process of separation.

If, for one reason or another, this process turns out to be impossible or impeded, the child is liable to feel as if a part of him- or herself has been cut off.

This traumatic organization of the psyche leaves its mark in the shape of "autistic islands" which fail to become integrated into the cycles of deferred effects and historical time: Their massiveness and their intensity, in autistic children, are an obstacle to their becoming part of mental functioning, and they end up serving as pathological poles of attraction for a whole variety of psychic elements which accrete within their sphere of influence and thus become incapable of dispersing in a manner at once orderly and differentiated.

In the wake of Frances Tustin, the post-Kleinian tendency in psychoanalysis has made wide use of the concept of the black hole, extending it to nonpsychotic subjects in whom autistic islands are possible even if in such cases they are less significant and less serious in their implications.

Bernard Golse

See also: Autism; Autistic capsule/nucleus; Breakdown.

Bibliography

Klein, Sydney. (1980). Autistic phenomena in neurotic patients. International Journal of Psycho-Analysis, 61 (2), 395-401.

Tustin, Frances. (1972). Autism and childhood psychosis. London: Hogarth; New York: Science House. Reprinted, London: Karnac, 1995.

——. (1986). Autistic barriers in neurotic patients. London: Karnac.

black hole An object with such a strong gravitational field that its escape velocity exceeds the velocity of light. One way in which black holes are believed to form is when massive stars collapse at the end of their lives. A collapsing object becomes a black hole when its radius has shrunk to a critical size, known as the Schwarzschild radius, and light can no longer escape from it. The surface having this critical radius is referred to as the event horizon, and marks the boundary inside which all information is trapped. Hence events within the black hole cannot be observed from outside. Theory indicates that both space and time become distorted inside the event horizon and that an object collapses to a single point, a singularity, at the centre of a black hole. Black holes may have any mass. Supermassive black holes (10⁵ solar masses) may exist at the centres of active galaxies. At the other extreme, mini black holes of radii 10^-10 m and masses similar to that of an asteroid may have been formed in the extreme conditions following the Big Bang.  No black hole has ever been observed directly. However, an accretion disk may form around a black hole when matter falls towards it from a nearby companion star or other source. Energy predominantly at X-ray wavelengths is produced as matter in the accretion disk loses momentum and spirals in; these X-rays can be detected by satellites in orbit. Several black-hole candidates have been located in our Galaxy, most famously Cygnus X-1. In addition, there is good evidence for a supermassive black hole of 3–4 million solar masses at the centre of our Galaxy.  There are several theoretically possible forms of black hole. A non-rotating black hole without electrical charge is known (after K.Schwarzschild) as a Schwarzschild black hole. A non-rotating black hole with electrical charge is termed a Reissner–Nordström black hole after the German physicist Hans Jacob Reissner (1874–1967) and the Finn Gunnar Nordström (1881–1923). In practice, black holes are likely to be rotating and uncharged, a form known as a Kerr black hole. Black holes are not entirely black; theory suggests that they can emit energy in the form of Hawking radiation.

black hole Postulated end-product of the total gravitational collapse of a massive star into itself following exhaustion of its nuclear fuel; the matter inside is crushed to unimaginably high density. It is an empty region of distorted space-time that acts as a centre of gravitational attraction; matter is drawn towards it, and once inside nothing can escape. Its boundary (the event horizon) is a demarcation line, rather than a material surface. Black holes can have an immense range of sizes. Since no light or other radiation can escape from black holes, they are extremely difficult to detect. Not all black holes result from stellar collapse. During the Big Bang, some regions of space might have become so compressed that they formed so-called primordial black holes Such black holes would not be completely black, because radiation could still ‘tunnel out’ of the event horizon at a steady rate, leading to the evaporation of the hole. Primordial black holes could therefore be very hot.

Black Hole

Modern astronomy has produced a theory about the life of stars in which the fate of a star crucially depends on how massive it is. Lighter stars might end as red dwarfs, and heavier stars as enormously dense but tiny neutron stars. The heaviest stars collapse in upon themselves, creating black holes. Black holes are called black because the gravitational force associated with them is so strong that no light can escape. The infinite gravitational attraction at the edge of an event horizon such as a black hole not only warps space but also warps time for the hypothetical observer near the black hole.

See also Astrophysics; Cosmology, Physical Aspects; Gravitation; Singularity

mark worthing

black hole • n. Astron. a region of space having a gravitational field so intense that no matter or radiation can escape. ∎ inf. a figurative place of emptiness or aloneness: they think he's sitting in a black hole with no interaction with his people. ∎ inf., chiefly humorous a place where money, lost items, etc., are supposed to go, never to be seen again: the moribund economy has been a black hole for federal funds. ∎ inf. (of a system, practice, or institution) a state of inadequacy or excessive bureaucracy in which hopes, progress, etc., become futile: juveniles lost for good in the black hole of the criminal justice system.

black hole A mythical location in a network where lost data or EMAILS end up. See also BIT BUCKET and BITOON.