Castor

Castor is a blue-white main-sequence star (spectral type A1V) about 51 light-years away. With an apparent magnitude of 1.58 it is a very bright, conspicuous star.

Six stars in one system that the naked eye sees as a single star.

Its light output is roughly 50 times that of the Sun (a rough estimate in visible light, calculated from brightness and distance).

From Germany (52° N) it rises and sets; it is best seen in the evening in January.