Stellar classification (astrophysics)
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Stars are classed by various properties. A common classification is surface temperature. Beginning with early spectral schema in the 19th century ranking stars from A to P, the spectral classification, called “Morgan-Keenan spectral classification” [1][2] now ranks stars in seven main types: O, B, A, F, G, K, M.[3] Each spectral classification is further divided into tenths. Our sun, Sol is a G2.
Classification system
The stars are ranked from hottest to coldest:
| Class | Temperature | Conventional color | Apparent color[4] | Mass [5] | Radius [6] | Luminosity [7] | Hydrogen lines | % of all MSSs[8][9] |
|---|---|---|---|---|---|---|---|---|
| O | 30,000–60,000 K | blue | blue | 60 M☉ | 15 R☉ | 1,400,000 L☉ | Weak | ~0.00003% |
| B | 10,000–30,000 K | blue white | blue white to white | 18 M☉ | 7 R☉ | 20,000 L☉ | Medium | 0.13% |
| A | 7,500–10,000 K | white | white | 3.1 M☉ | 2.1 R☉ | 80 L☉ | Strong | 0.6% |
| F | 6,000–7,500 K | yellowish white | white | 1.7 M☉ | 1.3 R☉ | 6 L☉ | Medium | 3% |
| G | 5,000–6,000 K | yellow | yellow | 1.1 M☉ | 1.1 R☉ | 1.2 L☉ | Weak | 8% |
| K | 3,500–5,000 K | orange | yellow orange | 0.8 M☉ | 0.9 R☉ | 0.4 L☉ | Very weak | 13% |
| M | 2,000–3,500 K | red | orange red | 0.3 M☉ | 0.4 R☉ | 0.04 L☉ | Very weak | >78% |
References
- ↑ Note: based on the work of Annie Cannon and other astronomers from the Harvard College Observatory
- ↑ Annie Jump Cannon 1983-1941
- ↑ A popular mnemonic for this is Oh Be A Fine Girl, Kiss Me
- ↑ The Colour of Stars. Australia Telescope Outreach and Education (December 21 2004). Retrieved on 2007-09-26. — Explains the reason for the difference in color perception.
- ↑ Solar Mass. Earth's sun is one solar mass. Equal to about 1.9891 X 10E30 kg or about 332,950 the mass of the earth
- ↑ Solar Radius. Earth's sun is the standard with one solar radius equal to about 6.960 X 10E8. This is about 110 times the radius of earth or 0.004652 AU (astronomical unit), the average distance of the earth from the sun
- ↑ Solar Luminosity. The standard is earth's sun equal to one solar luminosity. The luminosity of the sun is about 3.827 X 10E26 watts or 3.827 X 10E33 ergs
- ↑ MSS means Main Sequence Star
- ↑ LeDrew, G.; The Real Starry Sky, Journal of the Royal Astronomical Society of Canada, Vol. 95, No. 1 (whole No. 686, February 2001), pp. 32–33
- ↑ Star classification