Skylog

摘要

For those of us Who live in the northern latitudes, Castor and Pollux, the brightest stars of Gemini-the Twins-are nearly overhead around 10 p.m. local time on February 1, andrnaround 8 p.m. by month's end. The two stars were named in antiquity for the mythical sons of Leda, but in 1678 the Italian astronomer Giovanni Do-menico Cassini saw through an early telescope that one of them, Castor, was actually two stars, a fact rediscovered in 1718. Between 1719 and 1759, a change in angle between those two stars, dubbed Castor A and B, wasrnnoted, and in 1803 William Herschel, the German-born British astronomer and composer, demonstrated that they revolve around each other. It takes Castor A and B about 445 years tornmake the full circuit as they follow overlapping elliptical orbits.