Castor

Castor , bright star in the constellation Gemini ; Bayer designation α Geminorum; 1992 position R.A. 7 ^h 34.1 ^m , Dec. +31°54′. Slightly dimmer than Pollux , with which it forms the Twins, Castor has an apparent magnitude of 1.58, which still makes it one of the 25 brightest stars in the sky. Castor is actually a six-star system, being a visual triple each component of which is a binary star ; the three components are an eclipsing binary and a pair of spectroscopic binaries. The two brightest components are white, main-sequence stars of spectral classes A1 and A5. The system is about 50 light-years distant.

castor 1 beaver, unctuous substance obtained from the beaver (used as a drug). XIV. — (O)F. or L. castor — Gr. kástōr. The history of the use of castor oil (XVIII) for the pale-yellow oil obtained from the seeds of the plant Ricinus communis is obscure.

Castor The star Alpha Geminorum, which appears to the naked eye of magnitude 1.6 but which is actually a complex multiple star. A small telescope divides Castor into two stars of magnitudes 1.9 and 2.9, both A-type dwarfs, which orbit each other with a period of about 450 years. Each is a spectroscopic binary. There is a third star, known as Castor C or YY Geminorum, an eclipsing pair of M1 dwarfs that ranges from magnitude 9.2 to 9.6 in a period of 0.8 days. The six-star system lies 52 l.y. away.