Editing Subgiant (section)

===Properties===
This table shows the typical lifetimes on the main sequence (MS) and subgiant branch (SB), as well as any hook duration between core hydrogen exhaustion and the onset of shell burning, for stars with different initial masses, all at solar metallicity (Z = 0.02).  Also shown are the helium core mass, surface effective temperature, radius, and luminosity at the start and end of the subgiant branch for each star.  The end of the subgiant branch is defined to be when the core becomes degenerate or when the luminosity starts to increase.<ref name=pols>{{cite journal|bibcode=1998MNRAS.298..525P|title=Stellar evolution models for Z = 0.0001 to 0.03|journal=Monthly Notices of the Royal Astronomical Society|volume=298|issue=2|pages=525|last1=Pols|first1=Onno R.|last2=Schröder|first2=Klaus-Peter|last3=Hurley|first3=Jarrod R.|last4=Tout|first4=Christopher A.|last5=Eggleton|first5=Peter P.|year=1998|doi=10.1046/j.1365-8711.1998.01658.x|doi-access=free}}</ref>
{| class="wikitable"
|-
! rowspan=2 | Mass<br/>({{solar mass}}) !! rowspan=2 | MS (GYrs) !! rowspan=2 | Hook (MYrs) !! rowspan=2 | SB<br/>(MYrs) !! colspan=4 | Start !! colspan=4 | End !! rowspan=2 | Example
|-
! He Core ({{solar mass}}) !! T<sub>eff</sub> (K) !! Radius ({{solar radius}}) !! Luminosity ({{solar luminosity}}) !! He Core ({{solar mass}}) !! T<sub>eff</sub> (K) !! Radius ({{solar radius}}) !! Luminosity ({{solar luminosity}})
|- style="text-align:right;"
| 0.6 || 58.8 || N/A || 5,100 || 0.047 || style="background-color:#{{Color temperature|4763|hexval}}"|4,763 || 0.9 || 0.3 || 0.10 || 4,634 || 1.2 || 0.6 || [[Lacaille 8760|{{nowrap|Lacaille 8760}}]]
|- style="text-align:right;"
| 1.0 || 9.3 || N/A || 2,600 || 0.025 || style="background-color:#{{Color temperature|5766|hexval}}"|5,766 || 1.2 || 1.5 || 0.13 || 5,034 || 2.0 || 2.2 || The [[Sun]]
|- style="text-align:right;"
| 2.0 || 1.2 || 10 || 22 || 0.240 || style="background-color:#{{Color temperature|7490|hexval}}"|7,490 || 3.6 || 36.6 || 0.25 || 5,220 || 5.4 || 19.6 || [[Sirius]]
|- style="text-align:right;"
| 5.0 || 0.1 || 0.4 || 15 || 0.806 || style="background-color:#{{Color temperature|14544|hexval}}"|14,544 || 6.3 || 1,571.4 || 0.83 || 4,737 || 43.8 || 866.0 || [[Alkaid]]
|}

In general, stars with lower metallicity are smaller and hotter than stars with higher metallicity.  For subgiants, this is complicated by different ages and core masses at the [[main sequence turnoff]].  Low metallicity stars develop a larger helium core before leaving the main sequence, hence lower mass stars show a hook at the start of the subgiant branch.  The helium core mass of a Z=0.001 (extreme [[population II]]) {{solar mass|1}} star at the end of the main sequence is nearly double that of a Z=0.02 ([[population I]]) star.  The low metallicity star is also over 1,000 K hotter and over twice as luminous at the start of the subgiant branch.  The difference in temperature is less pronounced at the end of the subgiant branch, but the low metallicity star is larger and nearly four times as luminous.  Similar differences exist in the evolution of stars with other masses, and key values such as the mass of a star that will become a supergiant instead of reaching the red giant branch are lower at low metallicity.<ref name=pols/>