# Gravitational compression

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{{short description|Compression of a massive object by its own gravity}}

In [astrophysics](/source/astrophysics), '''gravitational compression''' is a phenomenon in which [gravity](/source/gravity), acting on the [mass](/source/mass) of an object, compresses it, reducing its size and increasing the object's [density](/source/density). 
 
[[File:Stellar core.gif|thumb|In the [core](/source/Solar_core) of a star such as the [Sun](/source/Sun), [gravitational](/source/gravitational) [pressure](/source/pressure) is balanced by the outward thermal pressure from [fusion reactions](/source/Nuclear_fusion), temporarily halting gravitational compression.]]
At the center of a [planet](/source/planet) or [star](/source/star), gravitational compression produces [heat](/source/heat) by the [Kelvin–Helmholtz mechanism](/source/Kelvin%E2%80%93Helmholtz_mechanism). This is the mechanism that explains how [Jupiter](/source/Jupiter) continues to [radiate](/source/radiation) heat produced by its gravitational compression.<ref name=SRI1>{{cite web | url = http://www.iki.rssi.ru/nineplanets/jupiter.html | title = Jupiter | publisher = Space Research Institute,Russian Academy of Sciences |access-date = 2009-11-05}}</ref>

The most common reference to gravitational compression is [stellar evolution](/source/stellar_evolution). The [Sun](/source/Sun) and other [main-sequence](/source/main_sequence) stars are produced by the initial [gravitational collapse](/source/gravitational_collapse) of a [molecular cloud](/source/molecular_cloud). Assuming the mass of the material is large enough, gravitational compression reduces the size of the core, increasing its [temperature](/source/temperature) until [hydrogen fusion](/source/hydrogen_fusion) can begin. This [hydrogen](/source/hydrogen)-to-[helium](/source/helium) [fusion reaction](/source/fusion_reaction) releases [energy](/source/energy) that balances the inward gravitational [pressure](/source/pressure) and the star becomes stable for millions of years. No further gravitational compression occurs until the hydrogen is nearly used up, reducing the thermal pressure of the fusion reaction.<ref>{{cite web |url = http://www.space.com/scienceastronomy/astronomy/star_formation_010116.html | title = How a Star is Born: Clouds Lift on Missing Link  | date = 16 January 2001 | author = R.R. Britt | website = [Space.com](/source/Space.com) | access-date = 2009-11-05}}</ref> At the end of the Sun's life, gravitational compression will turn it into a [white dwarf](/source/white_dwarf).<ref>
{{Cite web 
| title = White Dwarf Stars
| publisher = Astrophysics Science Division, NASA Goddard Space Flight Center.
| date =  November 2006
| url = http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html
| access-date = 2009-11-05
}}</ref>

At the other end of the scale are [massive stars](/source/Stellar_evolution). These stars burn their fuel very quickly, ending their lives as [supernova](/source/supernova)e, after which further gravitational compression will produce either a [neutron star](/source/neutron_star)<ref>
{{Cite web
| author = M. Coleman Miller
| title = Introduction to neutron stars
| publisher = [University of Maryland](/source/University_of_Maryland)
| url = https://www.astro.umd.edu/~miller/nstar.html
| access-date = 2009-11-05
}}</ref> or a [black hole](/source/black_hole)<ref>
{{Cite web
| author = N. Strobel
| title = Black Holes
| publisher = Nick Strobel's Astronomy Notes 
| date = June 2, 2007
| url = https://www.astronomynotes.com/evolutn/s13.htm
| access-date = 2009-11-05
}}</ref> from the remnants.

For planets and [moons](/source/natural_satellite), equilibrium is reached when the gravitational compression is balanced by a pressure gradient. This pressure gradient is in the opposite direction due to the strength of the material, at which point gravitational compression ceases.

==References==
<references/>

Category:Astrophysics

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Adapted from the Wikipedia article [Gravitational compression](https://en.wikipedia.org/wiki/Gravitational_compression) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Gravitational_compression?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.