Cosmic Scale
Sirius
White main-sequence star · 8.6 light-years
How big is Sirius?
Sirius is about 2,381,000 km across.
See Sirius in 3D, at true scale
Sirius is the brightest star in the night sky, partly because it is genuinely luminous and partly because it is close. It is a young white star with a white-dwarf companion, and it twinkles violently when low in the sky.
At a glance
| Diameter | 2,381,000 km |
|---|---|
| Mass | 4.10 × 10³⁰ kg |
| Diameter compared with Earth | 187 × Earth |
| Distance | 8.6 light-years |
| Brightness | 25 Suns |
| Surface | 9,940 K |
| Companion | Sirius B, a white dwarf |
Good to know
- The ancient Egyptians timed the Nile flood by its first appearance at dawn each year.
- Its name means 'scorching'; the hot days of summer are called dog days because it rises with the Sun then.
- It is moving closer, and will brighten slightly over the next 60,000 years.