Editing Gravitational collapse (section)

==Star formation==
{{Main|Star formation}}
An interstellar cloud of gas will remain in [[hydrostatic equilibrium]] as long as the [[kinetic energy]] of the gas [[pressure]] is in balance with the [[potential energy]] of the internal [[gravitational force]]. Mathematically this is expressed using the [[virial theorem]], which states that to maintain equilibrium, the gravitational potential energy must equal twice the internal thermal energy.<ref>{{cite book
 | first=Sun | last=Kwok | date=2006
 | title=Physics and chemistry of the interstellar medium
 | url=https://archive.org/details/physicschemistry0000kwok | url-access=registration | publisher=University Science Books 
 | isbn=1-891389-46-7 | pages=[https://archive.org/details/physicschemistry0000kwok/page/435 435–437]
}}</ref> If a pocket of gas is massive enough that the gas pressure is insufficient to support it, the cloud will undergo gravitational collapse. The critical mass above which a cloud will undergo such collapse is called the [[Jeans mass]]. This mass depends on the temperature and density of the cloud but is typically thousands to tens of thousands of [[solar mass]]es.<ref>{{cite book
 | first=Dina | last=Prialnik
 | title=An Introduction to the Theory of Stellar Structure and Evolution
 | publisher=[[Cambridge University Press]] | date=2000
 | isbn=0-521-65937-X | pages=198–199
}}</ref>