Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Stellar evolution
(section)
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
{{Short description|Changes to stars over their lifespans}} [[File:Representative lifetimes of stars as a function of their masses.svg|thumb|upright=1.35|Representative lifetimes of stars as a function of their masses]] [[File:Triangle of everything - Stellar Evolution.png | thumb|upright=1.35|A mass-radius plot (log) of multiple celestial bodies and their evolution: Nebulae merge into giant molecular clouds (top right), where regions contract into stellar nurseries, forming new stars and releasing heat. Matter condenses into clumps; smaller ones may become protoplanets or brown dwarfs, while larger ones trigger hydrogen fusion, creating stars. When hydrogen depletes, the star expands into a red giant, shedding its outer layers. The fate of its core depends on mass and can leave white dwarfs (low mass), neutron stars (high mass), or black holes (very massive stars). The expelled layers form a new nebula, continuing the cycle.]] [[File:Star Life Cycle Chart.jpg|thumb|upright=1.35|Chart of stellar evolution]] '''Stellar evolution''' is the process by which a [[star]] changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the current [[age of the universe]]. The table shows the lifetimes of stars as a function of their masses.<ref>{{cite book | first=Carlos A. | last=Bertulani |author-link=Carlos Bertulani | title=Nuclei in the Cosmos | publisher=World Scientific | date=2013 | isbn=978-981-4417-66-2}}</ref> All stars are formed from [[Gravitational collapse|collapsing]] clouds of gas and dust, often called [[nebula]]e or [[molecular cloud]]s. Over the course of millions of years, these [[protostar]]s settle down into a state of equilibrium, becoming what is known as a [[main sequence|main-sequence]] star. [[Nuclear fusion]] powers a star for most of its existence. Initially the energy is generated by the fusion of [[hydrogen atoms]] at the [[stellar core|core]] of the main-sequence star. Later, as the preponderance of atoms at the core becomes [[helium]], stars like the [[Sun]] begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the [[subgiant]] stage until it reaches the [[red giant|red-giant]] phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense [[white dwarf]] and the outer layers are expelled as a [[planetary nebula]]. Stars with around ten or more times the mass of the Sun can explode in a [[supernova]] as their inert iron cores collapse into an extremely dense [[neutron star]] or [[black hole]]. Although the [[universe]] is not old enough for any of the smallest [[red dwarf]]s to have reached the end of their existence, [[stellar model]]s suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.<ref name=endms>{{cite journal | last1 = Laughlin | first1 = Gregory | last2 = Bodenheimer | first2 = Peter | last3 = Adams | first3 = Fred C. | date = 1997 | title = The End of the Main Sequence | journal = The Astrophysical Journal | volume = 482 | issue = 1 | pages = 420β432 | doi = 10.1086/304125 | bibcode=1997ApJ...482..420L| doi-access = free }}</ref> Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating [[stellar structure]] using [[computer model]]s.
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)