Editing Star (section)

===Mass===
{{Main|Stellar mass}}
Stars have masses ranging from less than half the solar mass to over 200 solar masses (see [[List of most massive stars]]). One of the most massive stars known is [[Eta Carinae]],<ref>{{cite journal
 |first=Nathan
 |last=Smith
 |date=1998
 |url=http://www.astrosociety.org/pubs/mercury/9804/eta.html
 |title=The Behemoth Eta Carinae: A Repeat Offender
 |journal=Mercury Magazine
 |volume=27
 |issue=4
 |page=20
 |access-date=2006-08-13
 |url-status=dead
 |archive-url=https://web.archive.org/web/20060927091554/http://www.astrosociety.org/pubs/mercury/9804/eta.html
 |archive-date=2006-09-27
|bibcode=1998Mercu..27d..20S
 }}</ref> which, with 100–150&nbsp;times as much mass as the Sun, will have a lifespan of only several million years. Studies of the most massive open clusters suggests {{Solar mass|150}} as a rough upper limit for stars in the current era of the universe.<ref name= "weidner">{{Cite journal
 |title= Evidence for a fundamental stellar upper mass limit from clustered star formation
 |journal= Monthly Notices of the Royal Astronomical Society
 |date=2004-02-11 |pages= 187–191 |volume= 348 |issue= 1
 |doi= 10.1111/j.1365-2966.2004.07340.x
 |first1= C. |last1= Weidner |first2= P. |last2= Kroupa
 |doi-access= free
 |bibcode=2004MNRAS.348..187W|arxiv = astro-ph/0310860 |s2cid= 119338524
 }}</ref> This represents an empirical value for the theoretical limit on the mass of forming stars due to increasing radiation pressure on the accreting gas cloud. Several stars in the [[R136]] cluster in the [[Large Magellanic Cloud]] have been measured with larger masses,<ref name= "hainich">{{Cite journal | doi = 10.1051/0004-6361/201322696| title = The Wolf-Rayet stars in the Large Magellanic Cloud| journal = Astronomy & Astrophysics| volume = 565| pages = A27| year = 2014| last1 = Hainich | first1 = R.| last2 = Rühling | first2 = U.| last3 = Todt | first3 = H.| last4 = Oskinova | first4 = L. M.| last5 = Liermann | first5 = A.| last6 = Gräfener | first6 = G.| last7 = Foellmi | first7 = C.| last8 = Schnurr | first8 = O.| last9 = Hamann | first9 = W.-R. | arxiv = 1401.5474
| bibcode = 2014A&A...565A..27H| s2cid = 55123954}}</ref> but it has been determined that they could have been created through the collision and merger of massive stars in close binary systems, sidestepping the {{Solar mass|150}} limit on massive star formation.<ref name=banerjee>{{Cite journal |title= The emergence of super-canonical stars in R136-type starburst clusters |journal= Monthly Notices of the Royal Astronomical Society |date=2012-10-21 |pages= 1416–1426 |volume= 426 |issue= 2 |doi= 10.1111/j.1365-2966.2012.21672.x |first1= Sambaran |last1= Banerjee |first2= Pavel |last2= Kroupa |first3= Seungkyung |last3= Oh |doi-access= free |bibcode=2012MNRAS.426.1416B|arxiv = 1208.0826 |s2cid= 119202197 }}</ref>

[[File:Ngc1999.jpg|thumb|The [[reflection nebula]] [[NGC 1999]] is brilliantly illuminated by [[V380 Orionis]]. The black patch of sky is a vast hole of empty space and not a [[dark nebula]] as previously thought.]]
The first stars to form after the Big Bang may have been larger, up to {{Solar mass|300}},<ref>{{cite news
 | title=Ferreting Out The First Stars
 | publisher=Harvard-Smithsonian Center for Astrophysics
 | date=2005-09-22 | url=http://www.cfa.harvard.edu/news/2005/pr200531.html
 | access-date=2006-09-05}}</ref> due to the complete absence of elements heavier than [[lithium]] in their composition. This generation of supermassive [[population III stars]] is likely to have existed in the very early universe (i.e., they are observed to have a high redshift), and may have started the production of chemical elements heavier than [[hydrogen]] that are needed for the later formation of planets and life. In June 2015, astronomers reported evidence for Population III stars in the [[Cosmos Redshift 7]] galaxy at {{math|''z'' {{=}} 6.60}}.<ref name="AJ-20150604">{{cite journal
|last1=Sobral |first1=David |last2=Matthee |first2=Jorryt |last3=Darvish |first3=Behnam |last4=Schaerer |first4=Daniel |last5=Mobasher |first5=Bahram |last6=Röttgering |first6=Huub J. A. |last7=Santos |first7=Sérgio |last8=Hemmati |first8=Shoubaneh |title=Evidence For POPIII-Like Stellar Populations In The Most Luminous LYMAN-α Emitters At The Epoch Of Re-Ionisation: Spectroscopic Confirmation |date=2015-06-04|journal=[[The Astrophysical Journal]] | doi = 10.1088/0004-637x/808/2/139|arxiv = 1504.01734 |bibcode = 2015ApJ...808..139S |volume=808 |issue=2 |pages=139|s2cid=18471887 }}</ref><ref name="NYT-20150617">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Astronomers Report Finding Earliest Stars That Enriched Cosmos |url=https://www.nytimes.com/2015/06/18/science/space/astronomers-report-finding-earliest-stars-that-enriched-cosmos.html |date=2015-06-17 |work=[[The New York Times]] |access-date=2015-06-17}}</ref>

With a mass only 80&nbsp;times that of Jupiter ({{Jupiter mass}}), [[2MASS J0523-1403]] is the smallest known star undergoing nuclear fusion in its core.<ref name=SIMBAD>{{cite web
 |title=2MASS J05233822-1403022
 |url=http://simbad.u-strasbg.fr/simbad/sim-id?Name=2MASS%20J05233822-1403022&Ident=%40788130&submit=submit
 |publisher=SIMBAD – [[Centre de Données astronomiques de Strasbourg]]
 |access-date=2013-12-14}}</ref> For stars with metallicity similar to the Sun, the theoretical minimum mass the star can have and still undergo fusion at the core, is estimated to be about 75 {{Jupiter mass}}.<ref name="boss_planets_or_what">{{cite web
 |first=Alan
 |last=Boss
 |date=2001-04-03
 |url=http://www.carnegieinstitution.org/News4-3,2001.html
 |title=Are They Planets or What?
 |publisher=Carnegie Institution of Washington
 |access-date=2006-06-08
 |archive-url=https://web.archive.org/web/20060928065124/http://www.carnegieinstitution.org/News4-3%2C2001.html
 |archive-date=2006-09-28
 |url-status=dead
}}</ref><ref name="minimum">{{cite magazine
 |last=Shiga
 |first=David
 |date=2006-08-17
 |url=http://www.newscientistspace.com/article/dn9771-mass-cutoff-between-stars-and-brown-dwarfs-revealed.html
 |archive-url=https://web.archive.org/web/20061114221813/http://space.newscientist.com/article/dn9771-mass-cutoff-between-stars-and-brown-dwarfs-revealed.html
 |archive-date=2006-11-14
 |title=Mass cut-off between stars and brown dwarfs revealed
 |magazine=New Scientist
 |access-date=2006-08-23
 |url-status=dead
}}</ref> When the metallicity is very low, the minimum star size seems to be about 8.3% of the solar mass, or about 87 {{Jupiter mass}}.<ref name="minimum" /><ref>{{cite news
 | title=Hubble glimpses faintest stars
 | publisher=BBC | date=2006-08-18
 | url=http://news.bbc.co.uk/2/hi/science/nature/5260008.stm
 | access-date=2006-08-22
 | first=Elli
 | last=Leadbeater}}</ref> Smaller bodies called [[brown dwarf]]s, occupy a poorly defined grey area between stars and [[gas giant]]s.<ref name="boss_planets_or_what" /><ref name="minimum" />

The combination of the radius and the mass of a star determines its surface gravity. Giant stars have a much lower surface gravity than do main sequence stars, while the opposite is the case for degenerate, compact stars such as white dwarfs. The surface gravity can influence the appearance of a star's spectrum, with higher gravity causing a broadening of the [[absorption line]]s.<ref name="new cosmos" />