Gemini is a constellation of the Zodiac, Gemini depicts the mythological twins Castor and Pollux, after whom its two brightest stars are named. The twins sailed with the Argonauts in search of the golden fleece, and they were later regarded by the ancient Greeks as patrons of seafarers. The two stars themselves are not related, though, lying at different distances from us. Gemini sits between Taurus and Cancer, and the Sun passes through it from June 21st to July 20th.
Points of Interest
Alpha Geminorum (Castor)
A remarkable multiple star. To the naked eye, it appears as a single star of magnitude 1.6. A small telescope divides it into a blue-white pair of stars of magnitudes 1.9 and 2.9. These form a genuine binary with an orbital period of about 470 years. Both of these stars are spectroscopic binaries. A wider companion of 9th magnitude can also be seen with a small telescope. This is, in fact, a close pair of red dwarfs, forming an eclipsing binary. The whole six-star family is just over 50 light-years away.
Beta Geminorum (Pollux)
The brightest star in the constellation and among the 20 brightest in the sky, at magnitude 1.2. It is an orange-colored giant, 34 light-years away. The coloration is more noticeable when the star is viewed through binoculars.
M35 (Open Cluster)
M35 is a rich open cluster, just visible to the naked eye and easy to see with binoculars. It appears almost as large as the full Moon. Binoculars or a small telescope resolve its individual stars of 8th magnitude and fainter. The cluster lies nearly 3,000 light-years away.
NGC 2392 (Planetary Nebula)
A planetary nebula. Its bluish disk, similar in size to the globe of Saturn, is visible through a small telescope, but large apertures are needed to detect the surrounding features that lend it the appearance of a face and give rise to its popular names.