Limerick Astronomy Club: The Gemini Constellation

The Gemini constellation is located within the northern hemisphere and one of the signs of the zodiac (which co-ordinates to the apparent pathways of the sun, moon and planets). The constellations itself has been defined since ancient cultures and is one of those catalogued by Greek astronomer Ptolemy in the second century.

The name Gemini itself comes from the Latin term for ‘twins’, although the exact twins’ changes depending on the culture for which the constellation is identified. In Egyptian, the twins were referred to as twin goats, however in Arabian mythology it was known as twin peacocks. Nowadays, we tend to identify the twins in accordance with the Greek mythology, Castor and Pollux. The name Gemini has inspired a number of space initiatives including the Project Gemini spacecraft and the Gemini Observatory. Project Gemini was NASA’s second human space flight program which began in 1961 and ended in 1966.

The constellation itself is fairly easy to spot within the night sky, even for amateur astronomers. It can be located between the Taurus and Cancer constellations, northeast of the Orion constellation. During May it can be seen soon after sunset in the western night sky. Within this constellation the two main stars of Castor and Pollux can be located, referred to as the heads of the twins. Pollux is a giant red star and the brightest within this constellation (and the 17th brightest within the night sky). It is twice the size of our own Sun’s mass and about nine times its solar radius. Furthermore, in 2006 a planet orbiting this star was located. Castor, the second brightest star in this constellation (and 44th brightest overall) is also notable.

A number of notable objects can be located with this constellation also including a number of nebulas and neutron stars. The Eskimo nebula (NGC 2392) is a bipolar double-shell planetary nebula located 4,000 light years from Earth. The Medusa Nebula is pretty close at only 1,500 light years from earth. One of the best objects is a messier object known as M35. Messier 35 is an open start cluster which covers an area of the night sky as big as the full moon.

Email: limerickastronomy club@gmail.com