March 15, 2012

The Moon is at third quarter at 9:25 U.T. today.

Tonight, between the feet of Gemini, you see the pair of stars, Castor and Pollux. Castor is on top and Pollux is on the bottom. Castor is a most interesting object. It is 45 light-years away from Earth, and is the 23rd brightest star in the sky. Castor actually consists of three pairs of stars. Castor A consists of two spectral A type stars nearly identical in luminosity. These two stars orbit each other in only nine days. Castor B is also a pair of stars of spectral type A, however these two stars orbit each other in only three days. Castor A and Castor B can be seen as two separate stars in a small telescope. Castor C is a spectroscopic binary, two faint red stars so close to each other that they orbit each other in less than a day.

Designed and maintained by .
Updated September 4, 2011