Gravitational collapse in astronomy is the sudden inward fall of a massive body under the influence of the force of gravity. It occurs when all other forces fail to supply a sufficiently high pressure to counterbalance gravity and keep the massive body in (dynamical) equilibrium. Gravitational collapse is at the heart of the structure formation in the universe. An initial smooth distribution of matter will eventually collapse and cause the hierarchy of structures, such as clusters of galaxies, stellar groups, stars and planets. For example, a star is born through the gravitational collapse of a cloud of interstellar matter. The compression caused by the collapse raises the temperature until nuclear fuel ignites in the center of the star and the collapse comes to a halt. The thermal pressure gradient (leading to expansion) compensates the gravity (leading to compression) and a star is the dynamical equilibrium between these two forces. Lunar astronomy: the large crater is Daedalus, photographed by the crew of Apollo 11 as they circled the Moon in 1969. ... Gravity is a force of attraction that acts between bodies that have mass. ... REDIRECT [[ --68. ... Star formation is the process by which gas in molecular clouds change into the ball of plasma we call a star. ...

More specifically the term gravitational collapse refers to the gravitational collapse of a star at the end of its life time, also called the death of the star. When all stellar energy sources are exhausted, the interior of a star will undergo a gravitational collapse. In this sense a star is a "temporary" equilibrium state between a gravitational collapse at stellar birth and a gravitational collapse at stellar death. The end states are called compact stars, either white dwarfs or neutron stars. Very massive stars cannot find a new dynamical equilibrium; they keep contracting. They are said to undergo a continued gravitational collapse or catastrophic gravitational collapse. With increasing speed the stellar density increases beyond any bound to infinite densities and the stars shrinks in a time much less than a second to a pointlike object. This is a physical singularity, a problem unsolved in present day physics. At the final stage the density of matter is so high that current gravitational theories do not apply. Before the singular state is reached, however, the condensed matter has the properties of a black hole and the ultimate fate cannot be observed, in principle. In astronomy, stellar evolution is the sequence of changes that a star undergoes during its lifetime, the hundreds of thousands, millions or billions of years during which it emits light and heat. ... In astronomy, a compact star (sometimes called a compact object) is a star that is a white dwarf, a neutron star, a strange star, or a black hole. ... White dwarf Sirius-B in x-rays A white dwarf is an astronomical object which is produced when a low or medium mass star dies. ... Neutron stars are one of the few possible endpoints of stellar evolution. ... This article is in need of attention from an expert on the subject. ... A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). ...

The gravitational collapse of the interior of a star releases so much energy that the outer layers are blown away in an explosion. The remnants of explosions leading to the formation of white dwarfs are observed as planetary nebulae. Larger explosions, leading to the formation of a neutron star or black hole, are observed as supernovae, of which remnants can be observed. When the outer layers of a star are already removed (through a stellar wind for example), a catastrophic gravitational collapse can be seen as a gamma ray burst, a short flash of gamma rays lasting only seconds to minutes (see also gamma-ray astronomy). Each gamma ray burst marks the birth of a black hole, usually in a very distant galaxy. NGC 6543, the Cats Eye Nebula A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... Remnant of Keplers Supernova, SN 1604. ... In astronomy, gamma-ray bursts (GRBs) are flashes of gamma rays that last from seconds to hours, the longer ones being followed by several days of X-ray afterglow. ... This article is about electromagnetic radiation. ... Gamma-ray astronomy is the astronomical study of the cosmos with gamma rays. ...

Catastrophic gravitational collapse toward a black hole

Catastrophic gravitational collapse

A general relativistic description of catastrophic gravitational collapse has two points of view: as seen by a comoving observer and as seen by a distant (stationary) observer. Image File history File links Download high resolution version (571x644, 41 KB) Buzz Aldrin is taken by surprise when the Wikipedia logo undergoes a spontaneous gravitational collapse. ... Image File history File links Download high resolution version (571x644, 41 KB) Buzz Aldrin is taken by surprise when the Wikipedia logo undergoes a spontaneous gravitational collapse. ...

Viewed by a co-moving observer

An observer standing on a star in catastrophic gravitational collapse towards the black hole state undergoes a free fall (that is: in a comoving frame he does not feel gravity to first order). He only feels the tidal force (difference between the gravity on his head and his feet). This force increases beyond bounds as the star shrinks to a smaller radius. In the transverse direction the comoving observer during the catastrophic gravitational collapse will be squashed by the combination of the tidal force and the increasing curvature of space. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ...

This free fall will end in a finite proper time, with an infinite length and with thickness zero, while in the limit volume zero is reached and the density is increased to infinity.

The co-moving observer does not feel any particular force when he passes the Schwarzschild radius (the radius of a black hole, also called the event horizon). In other words, this radius is not a physical singularity. If the black hole is large, perhaps a supermassive black hole at the center of a galaxy, the tidal forces may not even be strong at this radius. However, his observations of the outside world change dramatically. During the fall he will see the horizon on the surface rising upward through the gravitational deflection of light. Just below the horizon he will see more and more light coming from the back of the star until he can see the entire stellar surface. At the same time the part of the sky above him is becoming a smaller and smaller region around his zenith. When he reaches the singularity, nothing is left of the outside world and he can't see any stars in the sky. Instead he sees the (shrinking) stellar surface in every direction. "Direction" becomes meaningless, or, rather, all directions become down. The Schwarzschild radius (sometimes inappropriately referred to as the gravitational radius[1]) is a characteristic radius associated with every mass. ... A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). ... Event Horizon is a 1997 science fiction and horror film. ... This article is in need of attention from an expert on the subject. ... Top: artists conception of a supermassive black hole drawing material from a nearby star. ... NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant. ...

Of course all of this observation are purely hypothetical - based on current mathematical presentations of black holes. As black holes are believed to be physical maximum entropy objects, vision-probes let alone a human eye of vanishingly low entropy, relatively speaking, could by no means be sustained. The principle of maximum entropy is a method for analyzing the available information in order to determine a unique epistemic probability distribution. ...

Before the free falling observer passes the Schwarzschild radius, a call for help signal can in principle reach the distant Earth or a spaceship. After passing this radius, all the signals he sends out will fall along with him in the gravitational collapse and never reach the outside world (hence the name event horizon). Event Horizon is a 1997 science fiction and horror film. ...

Hello there!!!.. My name is Kern. I like wearing odd shoes.. I need a haircut. I fancy ashlie. See ya around.. Come over my place in tadworth. 66 marbles way, tadworth, Surrey. UK... buhbye!!

Viewed by a distant (stationary) observer

A stationary observer at Earth or in a distant orbit will have an entirely different view on the catastrophic gravitational collapse. A clock of the free falling observer is in a stronger part of the gravitational field and when viewed from a distance appears to tick slower (gravitational time dilation). Also radiation is seen to tick slower and thus is observed at a longer wavelength (gravitational redshift). As the free falling observer (in his time) falls faster and faster toward the Schwarzschild radius, the stationary observer sees him progressing slower and slower towards the Schwarzschild radius and will never see him passing that stage. Instead the stationary observer will see collapse progressively dimmer and redder, until the entire star plus comoving observer disappears in much less than a second. The last photon the stationary observer will receive, comes from a stage of the collapsing star just outside the Schwarzschild radius. This article is in need of attention from an expert on the subject. ...

See also Scientific wager. A scientific wager is a wager whose outcome is settled by scientific method. ...