Editing Main sequence (section)

== Parameters ==
[[File:Morgan-Keenan spectral classification.svg|thumb|right|upright=1.2|Comparison of main sequence stars of each spectral class]]
By treating the star as an idealized energy radiator known as a [[black body]], the luminosity ''L'' and radius ''R'' can be related to the [[effective temperature]] ''T''<sub>eff</sub> by the [[Stefan–Boltzmann law]]:
: <math>L = 4 \pi \sigma R^2 T_\text{eff}^4</math>
where ''σ'' is the [[Stefan–Boltzmann constant]]. As the position of a star on the HR diagram shows its approximate luminosity, this relation can be used to estimate its radius.<ref name=ohrd/>

The mass, radius, and luminosity of a star are closely interlinked, and their respective values can be approximated by three relations. First is the Stefan–Boltzmann law, which relates the luminosity ''L'', the radius ''R'' and the surface temperature ''T''<sub>eff</sub>. Second is the [[mass–luminosity relation]], which relates the luminosity ''L'' and the mass ''M''. Finally, the relationship between ''M'' and ''R'' is close to linear. The ratio of ''M'' to ''R'' increases by a factor of only three over 2.5 [[orders of magnitude]] of ''M''. This relation is roughly proportional to the star's inner temperature ''T<sub>I</sub>'', and its extremely slow increase reflects the fact that the rate of energy generation in the core strongly depends on this temperature, whereas it has to fit the mass-luminosity relation. Thus, a too-high or too-low temperature will result in stellar instability.

A better approximation is to take {{nowrap|1=''ε'' = ''L''/''M''}}, the energy generation rate per unit mass, as ''ε'' is proportional to ''T<sub>I</sub>''<sup>15</sup>, where ''T<sub>I</sub>'' is the core temperature. This is suitable for stars at least as massive as the Sun, exhibiting the [[CNO cycle]], and gives the better fit {{nowrap|''R'' ∝ ''M''<sup>0.78</sup>}}.<ref>{{cite web |title=A course on stars' physical properties, formation and evolution |publisher=University of St. Andrews |url=http://www-star.st-and.ac.uk/~kw25/teaching/stars/STRUC4.pdf |access-date=2010-05-18 |archive-date=2020-12-02 |archive-url=https://web.archive.org/web/20201202003201/http://www-star.st-and.ac.uk/~kw25/teaching/stars/STRUC4.pdf |url-status=dead }}</ref>

=== Sample parameters ===
The table below shows typical values for stars along the main sequence. The values of [[luminosity]] (''L''), [[radius]] (''R''), and [[mass]] (''M'') are relative to the Sun—a dwarf star with a spectral classification of G2&nbsp;V. The actual values for a star may vary by as much as 20–30% from the values listed below.<ref name=siess00/>{{Why|date=December 2023}}

<!-- Please include a solid reference if you add additional values to this table. -->
{| class="wikitable"
|+ Table of main-sequence stellar parameters<ref name=zombeck/>
|-
! [[Stellar classification|Stellar <br/>class]]
! [[Radius]], <br/>''R''/{{solar radius|link=yes}}
! Mass, <br/>''M''/{{solar mass|link=yes}}
! Luminosity, <br/>''L''/{{solar luminosity|link=yes}}
! {{abbr|Temp.|Surface temperature}} <br/>([[kelvin|K]])
! Examples<ref name=simbad/>
|-
| O2 ||     12    ||     100   || 800,000 || class="mw-no-invert" style="background-color:#{{Color temperature|50000|hexval}}"|50,000
| style="text-align: left;" | [[BI 253]]
|-
| O6 || {{0}}9.8  || {{0}}35   || 180,000 || class="mw-no-invert" style="background-color:#{{Color temperature|38000|hexval}}"|38,000
| style="text-align:left;" | [[Theta1 Orionis C|Theta<sup>1</sup> Orionis C]]
|-
| B0 || {{0}}7.4  || {{0}}18   || {{0}}20,000  || class="mw-no-invert" style="background-color:#{{Color temperature|30000|hexval}}"|30,000
|style="text-align:left;"|[[Phi1 Orionis|Phi<sup>1</sup> Orionis]]
|-
| B5 || {{0}}3.8  || {{0|00}}6.5  || {{0|000,}}800     || class="mw-no-invert" style="background-color:#{{Color temperature|16400|hexval}}"|16,400
|style="text-align:left;"|[[Pi Andromedae|Pi Andromedae A]]
|-
| A0 || {{0}}2.5  || {{0|00}}3.2  || {{0|000,0}}80      || class="mw-no-invert" style="background-color:#{{Color temperature|10800|hexval}}"|10,800
|style="text-align:left;"|[[Alpha Coronae Borealis|Alpha Coronae Borealis A]]
|-
| A5 || {{0}}1.7  || {{0|00}}2.1  || {{0|000,0}}20      || class="mw-no-invert" style="background-color:#{{Color temperature|8620|hexval}}"|{{0}}8,620
|style="text-align:left;"|[[Beta Pictoris]]
|-
| F0 || {{0}}1.3  || {{0|00}}1.7  || {{0|000,00}}6       || class="mw-no-invert" style="background-color:#{{Color temperature|7240|hexval}}"|{{0}}7,240
|style="text-align:left;"|[[Gamma Virginis]]
|-
| F5 || {{0}}1.2  || {{0|00}}1.3 || {{0|000,00}}2.5     || class="mw-no-invert" style="background-color:#{{Color temperature|6540|hexval}}"|{{0}}6,540
|style="text-align:left;"|[[Eta Arietis]]
|-
| G0 || {{0}}1.05 || {{0|00}}1.10 || {{0|000,00}}1.26    || class="mw-no-invert" style="background-color:#{{Color temperature|5920|hexval}}"|{{0}}5,920
|style="text-align:left;"|[[Beta Comae Berenices]]
|-
| G2
| {{n/a|align=left|{{0}}1{{0|.00}}}}
| {{n/a|align=left|{{0|00}}1{{0|.00}}}}
| {{n/a|align=left|{{0|000,00}}1{{0|.00}}}}
| class="mw-no-invert" style="background-color:#{{Color temperature|5780|hexval}}"|{{0}}5,780
|style="text-align:left;"| '''[[Sun]]'''<ref name=bydef group=note>The Sun is a typical type G2V star.</ref>
|-
| G5 || {{0}}0.93 || {{0|00}}0.93 || {{0|000,00}}0.79    || class="mw-no-invert" style="background-color:#{{Color temperature|5610|hexval}}"|{{0}}5,610
|style="text-align:left;"|[[Alpha Mensae]]
|-
| K0 || {{0}}0.85 || {{0|00}}0.78 || {{0|000,00}}0.40    || class="mw-no-invert" style="background-color:#{{Color temperature|5240|hexval}}"|{{0}}5,240
|style="text-align:left;"|[[70 Ophiuchi|70 Ophiuchi A]]
|-
| K5 || {{0}}0.74 || {{0|00}}0.69 || {{0|000,00}}0.16    || class="mw-no-invert" style="background-color:#{{Color temperature|4410|hexval}}"|{{0}}4,410
|style="text-align:left;"|[[61 Cygni|61 Cygni A]]<ref name=apj129/>
|-
| M0 || {{0}}0.51 || {{0|00}}0.60 || {{0|000,00}}0.072   || class="mw-no-invert" style="background-color:#{{Color temperature|3800|hexval}}"|{{0}}3,800
|style="text-align:left;"|[[Lacaille 8760]]
|-
| M5 || {{0}}0.18 || {{0|00}}0.15 || {{0|000,00}}0.0027  || class="mw-no-invert" style="background-color:#{{Color temperature|3120|hexval}}"|{{0}}3,120
|style="text-align:left;"|[[EZ Aquarii|EZ Aquarii A]]
|-
| M8 || {{0}}0.11 || {{0|00}}0.08 || {{0|000,00}}0.0004  || class="mw-no-invert" style="background-color:#{{Color temperature|2650|hexval}}"|{{0}}2,650
| style="text-align:left;" |[[VB 10|Van Biesbroeck's star]]<ref name=recons/>
|-
| L1 || {{0}}0.09 || {{0|00}}0.07 || {{0|000,00}}0.00017 || class="mw-no-invert" style="background-color:#{{Color temperature|2200|hexval}}"|{{0}}2,200
| style="text-align:left;" | [[2MASS J0523−1403]]
|}

[[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]]