Two for one winter constellations

This week we get a two-for-one on our winter constellation, it is Gemini, the Twins.

The constellation can be found to the left of Orion. Draw and extend a line from Orion's left knee (Rigel) through his right shoulder (Betelgeuse) and you will find the feet of Gemini. With its location next to Orion it appears that the twins are standing in the starry river formed by the Milky Way.

Gemini has the form of a rectangle with its two brightest stars, Castor and Pollux, on the left end (as you are looking at it). The constellation is lying almost parallel with the eastern horizon when it rises at about the same time as Orion.

There is much in mythology associated with Castor and Pollux. They joined Jason and the Argonauts in search of the Golden Fleece, were involved in many battles, and were also involved in some rather nefarious deeds such as cattle rustling and wife stealing. Their sister was Helen of Troy who started a long battle in her own right, the Trojan war.

While both are first magnitude stars, Castor is slightly brighter thus earning the alpha designation for the constellation and is located on the upper side of the left end of the rectangle (as you are looking at it).

If you have a modest telescope it will show Castor as a double star, if you have a larger telescope it will show Castor as a triple star system. The really big professional telescopes will show that all three stars are doubles in their own right. Pollux is a red giant star.

Gemini is the third sign of the zodiac with the Sun residing there from May 22 to June 21 thus being a zodiacal spring sign. In reality however, Gemini rises with the winter constellations.

There is one Messier object located in Gemini. M35 can be found just two degrees above the foot of Castor.

It is a bright open cluster with about 200 stars and makes a fine sight in binoculars or a small telescope or a larger telescope on low power. A smaller, dimmer, star cluster, NGC 2158, at magnitude 11, is located right next to M35 but will take a larger telescope to see it.

There is also a fine meteor shower associated with Gemini, the Geminid shower, which peaks around December 13 and 14 each year, and they were a fine show this past month. They appear to radiate from the area around Castor.

Some astronomical history is involved with Gemini. It was here that the planet Pluto, oops, excuse me, the former planet Pluto and the planet Uranus were discovered in 1930 and 1781 respectively.

SKY WATCH: Full Moon, February 2 which is also Groundhog Day, or from the old almanac, Candlemas Day which marks the halfway point of winter. Look to the west about an hour before sunrise on February 3 for a fine conjunction of Saturn, the Moon, and Regulus. On Feb. 7, about 45 minutes after sunset, take your binoculars to a place where you will have a flat western horizon and watch the conjunction of Mercury and Venus. Use the binoculars to find the planet Uranus just slightly above Venus.

Next time, the Hexagon and the Triangle.