Main Sequence Star Data Spectral Types
Spectral Absolute Luminosity Effective Wavelength Max Mass Radius Mean Density
Type m_Visual (L_sun) Temperature (microns) (M_sun) (R_sun) (g/cm**3)
(K)
O5 -5.8 501,000 40,000 .0724 40 17.8 0.01
B0 -4.1 20,000 28,000 .100 18 7.4 0.1
B5 -1.1 790 15,000 .190 6.4 3.8 0.2
A0 0.7 79 9,900 .290 3.2 2.5 0.3
A5 2.0 20 8,500 .340 2.1 1.7 0.6
F0 2.6 6.3 7,400 .390 1.7 1.4 1.0
F5 3.4 2.5 6,600 .440 1.3 1.2 1.1
G0 4.4 1.3 6,000 .480 1.1 1.0 1.4
G5 5.1 0.8 5,500 .520 0.9 0.9 1.6
K0 5.9 0.4 4,900 .590 0.8 0.8 1.8
K5 7.3 0.2 4,100 .700 0.7 0.7 2.4
M0 9.0 0.1 3,500 .830 0.5 0.6 2.5
M5 11.8 0.01 2,800 1.0 0.2 0.3 10.0
M8 16 0.001 2,400 1.2 0.1 0.1 63
Notes:
- The data was taken from
Se-604--605
But comparable data can be found in
Cox-388ff.
- Spectral type is a classification of stars according to their line spectra.
Originally, they classed as A, B, C, etc. according in decreasing order ???
of the strength of hydrogen lines
(No-484--485).
But this ordering didn't fit well with physical properties as these became
known, and so the types were rearranged into the modern OBAFGKM ordering that
does correlate with physical properties as can be seen above.
The types are each divided into sub-types that run 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
The re-ordering of the types was largely the work of Annie Jump Cannon
(1863--1941) at the Harvard College Observatory (HCO) which she joined
in 1895 in the lowly job of computer---before their were electronic computers
there were ... Henry Norris Russell (1877--1957) thought up the mnemonic
for remembering the sequence: ``O be a fine girl kiss me:'' modern
versions allow girl/guy: in any case sometimes there's nothing else worth saying.
In fact, I had a passing acquaintance with Fred Whipple (1906--2004: inventor
of the dirty snowball theory of comets) over the cookie table at the HCO
colloquiums in the earlier 1990s, and he well remembered Cannon and Russell.
- The Sun is NOT a special star in a fundamental sense, but it's special
to us and it is conveniently in the middle range of main sequence stars.
Thus we use it as a standard and often give luminosity, mass, and radii
in solar units. That is done in the table above.
The Sun is actually a G2 star which has properties intermediate between
the G0 and G5 types given on the table.
- I imagine luminosity is total luminosity over the whole electromagnetic
sequence, but source table doesn't say.
- Effective temperature is the temperature of the visible surface of
the star speaking loosely. The interior temperatures go up to tens of
millions of degrees Kelvin. The
Kelvin temperature scale
is the absolute temperature scale.
Note T_K=T_C+273.15, where T_K is Kelvin temperature, T_C is Celsius
temperature, and -273.15 degrees Celsius or 0 Kelvins is absolute zero.
- The density of water is almost exactly 1 g/cm**3, and so main sequence
mean densities arn't much different in the middle of the sequence.
The mean density of the Sun is about 1.4 g/cm**3
(Cl-165).
Central densities, on the other hand, can be much larger:
the Sun's central density is about 160 g/cm**3
(Cl-483).