Castor
Also known as α Gem · HR 2891
Castor is a spectroscopic binary star in the constellation Gemini.
Facts
| Type | Spectroscopic binary star (spectral type A1.5IV+) |
|---|---|
| Constellation | Gemini |
| Position (J2000) | 7h 34m 35s, +31° 53′ |
| Brightness | magnitude 1.9 (smaller is brighter; the faintest stars the eye sees are about 6) |
| Studied in | 395 scientific papers (SIMBAD) |
When and how to see it
Castor is highest in the sky at midnight in January. From India (about 20° N) it climbs to about 78° above the horizon; from 50° N, to about 72°. To see it you need the naked eye, even from a town.
Heights are worked out for India and for 50° N. Set your location in Settings to see them for where you are.
For tonight's best time from your own town, the darkness and the Moon, open it on the map and see its "Tonight from your location" card.
More in Gemini
Everything in Gemini · All 88 constellations · All sky objects
Data: SIMBAD (CDS, Strasbourg; the site's weekly copy) · Data sources & credits