Castor is a white main sequence star in the constellation Gemini. it is the second brightest star in said constellation, although its Bayer designation is α Geminorum. It is a 6 star system, Composed of two white main sequence stars and four red dwarf stars. The two components of Castor C are also known as YY Geminorum.
Astronomical data
Castor Aa
Radius (in Solar Radii): 2.08 R☉
Diameter (in Kilometers): 2,907,888 km
Mass (in Solar Masses): 2.37 M☉
Distance (in Light Years): 49.15 ly
Spectral type: A1V (White)
Castor Ba
Radius (in Solar Radii): 1.64 R☉
Diameter (in Kilometers): 2,294,016 km
Mass (in Solar Masses): 1.78 M☉
Spectral type: Am (White)