Magnitude 1.78, blue-white. Comfortably visible to the naked eye from a suburban sky.
Castor shines at magnitude 1.78, making it comfortably visible to the naked eye from a suburban sky. Its B−V colour index of -0.22 makes it blue-white to the eye, corresponding to a surface temperature of over 10,000 K.
It sits at right ascension 8.16 hours and declination -47.3°. It lies south of the celestial equator and sits low for northern observers, better the further south you go.
SkyRef shows exactly where Castor is from your location right now — altitude, compass direction, and rise and set times.