Editing Star (section)

===Luminosity===
The luminosity of a star is the amount of light and other forms of [[radiant energy]] it radiates per unit of time. It has units of [[power (physics)|power]]. The luminosity of a star is determined by its radius and surface temperature. Many stars do not radiate uniformly across their entire surface. The rapidly rotating star [[Vega]], for example, has a higher [[energy flux]] (power per unit area) at its poles than along its equator.<ref>{{cite news
 | author=Staff
 | date=2006-01-10
 | title=Rapidly Spinning Star Vega has Cool Dark Equator
 | publisher=National Optical Astronomy Observatory
 | url=http://www.noao.edu/outreach/press/pr06/pr0603.html
 | access-date=2007-11-18
 | archive-date=2019-05-24
 | archive-url=https://web.archive.org/web/20190524103812/https://www.noao.edu/outreach/press/pr06/pr0603.html
 | url-status=dead
 }}</ref>

Patches of the star's surface with a lower temperature and luminosity than average are known as [[sunspot|starspots]]. Small, ''dwarf'' stars such as the Sun generally have essentially featureless disks with only small starspots. ''Giant'' stars have much larger, more obvious starspots,<ref name= "Michelson Starspots">{{cite journal
 |last1=Michelson |first1=A. A. |last2=Pease |first2=F. G.
 |title=Starspots: A Key to the Stellar Dynamo |journal=Living Reviews in Solar Physics
 |volume=2 |issue=1 |pages=8 |date=2005
 |url=http://solarphysics.livingreviews.org/Articles/lrsp-2005-8/|bibcode=2005LRSP....2....8B |doi=10.12942/lrsp-2005-8 |doi-access=free }}</ref> and they exhibit strong stellar [[limb darkening]]. That is, the brightness decreases towards the edge of the stellar disk.<ref>{{cite journal
 |last1=Manduca |first1=A. |last2=Bell |first2=R. A. |last3=Gustafsson |first3=B.
 |title=Limb darkening coefficients for late-type giant model atmospheres
 |journal=Astronomy and Astrophysics |date=1977 |volume=61 |issue=6 |pages=809–813
 |bibcode=1977A&A....61..809M}}</ref> Red dwarf [[flare star]]s such as [[UV Ceti]] may possess prominent starspot features.<ref>{{cite journal   |last1=Chugainov |first1=P. F.
 |title=On the Cause of Periodic Light Variations of Some Red Dwarf Stars
 |journal=Information Bulletin on Variable Stars |date=1971 |volume=520 |pages=1–3 |bibcode=1971IBVS..520....1C}}</ref>