Gemini, the Twins
Many cultures have seen two humans in this star pattern — marked by two roughly parallel lines of stars capped by two of the brightest stars in our night sky. But the legend that endures is that of Castor and Pollux. Gemini's two brightest stars bear the names of the twins.
Pollux is the brighter of the twins. The orange-giant star is about 35 light-years from Earth. At least one planet orbits the star. It is at least three times as massive as Jupiter, and it orbits Pollux once every 1.6 years.
Castor consists of six stars — a cosmic sextet locked in a gravitational ballet. This crowded system lies about 50 light-years from Earth.
The star cluster M35 stands near the "feet" of the twins. It is about 2,800 light-years away, and it contains a couple of thousand stars. Astronomers estimate that the cluster is well more than 100 million years old. The stars all started with roughly the same amounts of hydrogen, helium, and other elements. By studying how much of these elements the stars have today, astronomers learn a great deal about how stars evolve.
The constellation is home to the Geminid meteor shower, which peaks in mid-December. If you trace their paths across the sky, the meteors all point back toward Gemini.
