Castor was a great horseman and fighter. One of his pupils was Heracles. Like Heracles, both Castor and Pollux would become Argonauts, that is, join Jason in his quest for the golden fleece. The twins spent their time raiding cattle and abducting young women, as Greek gods were wont to do. During one such cattle raid a cousin (Idas) became enraged at Castor and killed him. Zeus threw a thunderbolt at Idas, killing him instantly. Read more
Castor ( Gem / Geminorum / Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. Although it has the Bayer designation "alpha", it is actually fainter than Beta Geminorum (Pollux).
In a small telescope at 80x or so, Castor resolves into two bright stars. The A component has magnitude 2.0 and lies some 4" from the slightly fainter B component. These stars take some 400 years to revolve around each other in an elliptical orbit. In 100 years, the stars will increase their apparent separation to about 6". At their closest, the two stars lie only 1.8" apart. Castor A and B are blue-white A-type stars only 45 light-years from the Sun.