Explanation
This is a memory sentence to help you remember the spectral classes of stars, in order of decreasing surface temperature. Take the first letter of each word: Oh, Be A Fine Girl, Kiss Me! → O-B-A-F-G-K-M.
Each class also has a rough color and surface temperature:
- O: blue, the hottest class (over 30,000 K)
- B: blue-white (10,000-30,000 K)
- A: white (7,500-10,000 K)
- F: yellow-white (6,000-7,500 K)
- G: yellow (5,200-6,000 K); our Sun is class G2
- K: orange (3,700-5,200 K)
- M: red, the coolest class (under 3,700 K)
Variations
- Oh, Be A Fine Guy, Kiss Me!
- Oh, Be A Fine Gentleman, Kiss Me!