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 

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Notes:
1. The data was taken from Se-604--605 But comparable data can be found in Cox-388ff.

2. 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.

3. 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.

4. I imagine luminosity is total luminosity over the whole electromagnetic sequence, but source table doesn't say.

5. 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.

6. 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).

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