Absolute Magnitude
To compare stars, astronomers compute their absolute magnitudes. The absolute magnitude of a star is the magnitude it would have if viewed from the standard distance of 10 parsecs (32 light years).
Alpha and Beta Centauri are of comparable visual magnitude. When the stars are arranged by absolute magnitude, the two stars are seen to be widely different. Alpha Centauri, which the eye sees as the brighter star, moves down towards the bottom of the list. Its apparent brightness is due to its extreme closeness. Beta Centauri, over 100 times further away, is nearly 10,000 times more luminous than Alpha Centauri.
Note: The eye sees only the brighest stars. To gain a true picture of the number of stars and the distribution of their luminosities, telescopes and long-exposure photograpy must be employed. Gliese and Jahreiss have tabulated the magnitudes and distances of 3,803 nearby stars. Most of the stars in their list are less luminous than the Sun - when sorted in order of absolute brightness, the Sun occupies 527th place out of 3803.
Number of stars by spectral type:
Spectral Type Number of Stars
Brightest
O 0
B 3
A 75
F 267
G 506 (The Sun is a G star)
K 902
M 1,743 (Proxima Centauri is an M star)
white dwarfs 91
Dimmest
across the full range of visual magnitudes.
Move the mouse pointer over the links below to locate stars
| Object | Abs Mag | Luminosity | Distance |
| Beta Centauri | -5.4 | 12,300 Suns | 525 ly |
| Alpha Crucis | -4.2 | 3,960 Suns | 321 ly |
| Beta Crucis | -3.9 | 3,070 Suns | 353 ly |
| Delta Crucis | -2.5 | 790 Suns | 364 ly |
| BL Crucis | -0.8 | 177 Suns | 566 ly |
| Epsilon Crucis | -0.6 | 149 Suns | 228 ly |
| Gamma Crucis | -0.6 | 140 Suns | 88 ly |
| Iota Crucis | 1.8 | 16 Suns | 125 ly |
| Alpha Centauri | 4.3 | 1.4 Suns | 4.3 ly |
| Sun | 4.6 | 1 Sun | - ly |
| Proxima Centauri | 15.4 | 0.0005 Suns | 4.2 ly |
Proxima Centauri is the next closest star after the Sun. Its position is indicated on the image, but it is far too dim to be seen at this resolution.