The Sirius System
[1] - [2] - [3] - [4] - [5]Sirius is a binary star. By eye we see the larger partner, Sirius A. Sirius A is about 2.4 times more massive than the Sun and shines with about 20 times the Sun's luminosity.
Sirius B is much smaller than Sirius A. It is much hotter than Sirius A, but has exhausted its fuel and fusion has ceased. Sirius B is the degenerate core of a star - a white dwarf with the mass of the Sun, but the size of Earth.
| Object | Radius | Mass | Temperature |
| Sirius A | 1.3 | 2.4 | 9,000°K |
| Sirius B | 0.007 | 1.0 | 28,000°K |
| The Sun | 1.0 | 1.0 | 6,700°K |
| Earth | 0.01 | 0.000002 | 300°K |
Sirius A is much brighter than Sirius B in visible light.
MacDonald Observatory Image