numbers of stars
The exact number of stars in the Galaxy is not known but probably lies in the range 200 to 400 billion. Just as smaller creatures tend to be more numerous than larger ones, so there is a direct relationship between the mass (and luminosity) of main sequence stars and their abundance. The figures in the table below assume a total stellar population in our Galaxy of 400 billion stars; they are very approximate and do not include brown dwarfs.
| spectral type | typical mass (Msun) | brightnes (Lsun) | percentage of total | number of stars |
| O | 32 | 50,000 | 0.00002 | 56,000 |
| B | 6 | 300 | 0.09 | 360,000,000 |
| A | 2 | 10 | 0.6 | 2,400,000,000 |
| F | 1.25 | 2 | 2.9 | 12,000,000,000 |
| G | 0.9 | 0.9 | 7.3 | 28,000,000,000 |
| K | 0.6 | 0.2 | 15.1 | 60,000,000,000 |
| M | 0.2 | 0.005 | 73.2 | 293,000,000,000 |
