Prominent in the January night sky, the constellation of Gemini (Latin for "twins"), visible all night long, can be found to the upper left (east) of Orion - the Hunter.
Although associated with a number of ancient myths concerning twins, the one that is most familiar to sky observers is that of Castor and Polydeuces (Pollux in Latin). The twin brothers, Castor and Polydeuces, were born of one mother and two fathers. Their mother was Leda, Queen of Sparta, whilst their fathers were the mortal Tyndareus (King of Sparta) and the immortal Zeus, god and ruler of Olympus. Castor was the son of Leda and Tyndareus, and was mortal. Polydeuces, however, was immortal, the product of Zeus's infamous seduction (in the form of a swan) of Queen Leda.
The two brothers were inseparable throughout their lives. They and their twin cousins, Idas and Lynceus (sons of Tyndareus's half-brother,) joined Jason and the Argonauts on their famous quest for the golden fleece. During a heated argument between the cousins, Castor was slain (by Idas), as were Idas (by Polydeuces for killing Castor) and Lynceus (by Zeus, when he attempted to kill Polydeuces). Inconsolable at the loss of his slain brother, Polydeuces refused immortality if Castor could not share it. Zeus took pity on Polydeuces, and agreed to let the twin brothers share half their time together in the heavens and the other half in the earth (thus Gemini is not visible in the summer night sky). To honour their brotherly love, Zeus placed their forms in the night sky.
Roman mythology associated the constellation of Gemini with the story of the twin brothers, Romulus and Remus, who were said to have founded the city of Rome and, subsequently, the Roman Empire.
The constellation's two prominent stars - Castor and Pollux - are very different in appearance. The brighter of the two, Pollux (apparent magnitude of +1.14), is a red giant at a distance of approximately 34 light years to Earth, while Castor is a blue-white star, located about 52 light years away, and having an apparent magnitude of +1.6. Castor is actually a sextuplet (six) star system, with the two stars Castor A (mag. +1.93) and Castor B ) mag. +2.97) the most visually apparent.
The Geminids in mid-December are the most famous meteor shower associated with this constellation, and, with an average hourly rate (from a dark site) of 100+ meteors, are considered one of the year's best.
Venus, as it has for the past few weeks, remains the only bright planet visible in the early evening sky, appearing in the southwest sky at dusk, and remaining in view until about 3 hrs after sunset. Mars is the only early morning planet through the first half of January. It rises about 50 minutes before the sun in the southeast sky, and is visible until lost in the glow of sunrise. Look for Mars to the upper left of Antares, the bright "heart star" of Scorpius - the Scorpion, low on the southeast horizon. Compare the reddish hues of Mars and Antares in binoculars, and you will understand why Antares means "rival of Mars".
Mercury and Jupiter are still too close to the sun to be seen, but will put in an appearance in the latter part of the month. Likewise, Saturn sits too close to the sun at present, and although it will pass behind the sun (superior conjunction) on Jan. 13, it won't become visible in the eastern, pre-dawn sky until early February.
Until next time, clear skies.
Events:
Jan. 17 - Last quarter moon
Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. He welcomes comments from readers, and anyone who would like to do so is encouraged to email him at [email protected].
