Editing Red-giant branch (section)

===Tip of the red-giant branch===
{{Main | Tip of the red-giant branch}}
For stars with a degenerate helium core, there is a limit to this growth in size and luminosity, known as the [[tip of the red-giant branch]], where the core reaches sufficient temperature to begin fusion. All stars that reach this point have an identical helium core mass of almost {{solar mass|0.5}}, and very similar stellar luminosity and temperature. These luminous stars have been used as standard candle distance indicators. Visually, the tip of the red-giant branch occurs at about absolute magnitude −3 and temperatures around 3,000 K at solar metallicity, closer to 4,000 K at very low metallicity.<ref name=vandenberg/><ref name=lee>{{cite journal|bibcode=1993ApJ...417..553L|title=The Tip of the Red Giant Branch as a Distance Indicator for Resolved Galaxies|journal=Astrophysical Journal |volume=417|pages=553|last1=Lee|first1=Myung Gyoon|last2=Freedman|first2=Wendy L.|last3=Madore|first3=Barry F.|year=1993|doi=10.1086/173334|doi-access=free}}</ref> Models predict a luminosity at the tip of {{solar luminosity|2000–2500}}, depending on metallicity.<ref name=salaris11997>{{cite journal|bibcode=1997MNRAS.289..406S|arxiv=astro-ph/9703186|title=The 'tip' of the red giant branch as a distance indicator: Results from evolutionary models|journal=Monthly Notices of the Royal Astronomical Society|volume=289|issue=2|pages=406|last1=Salaris|first1=Maurizio|last2=Cassisi|first2=Santi|year=1997|doi=10.1093/mnras/289.2.406|doi-access=free |s2cid=18796954}}</ref> In modern research, infrared magnitudes are more commonly used.<ref name=conn>{{cite journal|doi=10.1088/0004-637X/758/1/11|arxiv=1209.4952|title=A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude. Ii. Distances to the Satellites of M31|journal=The Astrophysical Journal|volume=758|issue=1|pages=11|year=2012|last1=Conn|first1=A. R.|last2=Ibata|first2=R. A.|last3=Lewis|first3=G. F.|last4=Parker|first4=Q. A.|last5=Zucker|first5=D. B.|last6=Martin|first6=N. F.|last7=McConnachie|first7=A. W.|last8=Irwin|first8=M. J.|last9=Tanvir|first9=N.|last10=Fardal|first10=M. A.|last11=Ferguson|first11=A. M. N.|last12=Chapman|first12=S. C.|last13=Valls-Gabaud|first13=D.|bibcode = 2012ApJ...758...11C |s2cid=53556162}}</ref>