Star
The fainter of the twins of Gemini, appearing as one star to the eye but resolving into a system of six stars in three binary pairs.
| Type | Star |
|---|---|
| Distance from Earth | 49 ly |
| Diameter | 2,906,000 km |
| Mass | 4.72 × 10^30 kg |
| Temperature | 10,013°C |
| Apparent magnitude | 1.58 |
| Redshift | 0 |
| Discovered | 150 |
At 2,906,000 km across, Castor is 2.1 times the diameter of the Sun.
Its mass is 2.4 times the mass of the Sun.
The light reaching us from Castor tonight left it around 49 years ago.
Its surface sits at 10,286 K, hotter than the Sun at 5,772 K, which is what sets its colour.
It has been on record since the year 150.
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