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Welcome to December’s edition of Eyes on the Night Sky. This month heralds the Christmas season, with many of us putting up beautiful light displays to celebrate this joyous time. Take time this month to get outside and look up at the natural Christmas lights, preferably in a place with little or no light pollution. There are plenty of celestial treats to be discovered with the unaided eyes, binoculars and telescopes. We have selected a few of many visual wonders, including a great meteor shower.

The Constellation of Gemini
Click the image below to reveal the position of the Gemini Constellation.

Although there are many months during the year when the constellation of Gemini can be observed, the months between December and February are the best times to learn about this twin constellation. It rises in the east at around 5pm from the beginning of December and is in the sky all through the night. Its two brightest stars, Castor and Pollox make it easy to spot where this constellation lies, which is next to the constellation of Orion. Find Orion’s red supergiant Betelgeuse, and the stars Castor and Pollux like at the 10 o’ clock position. The two stars represent the twin's heads – try and make out the ‘stick men’ shape of this constellation. According to Greek mythology, Castor was the mortal son of the king of Sparta, Tyndareus and Pollux, the immortal son of the god Zeus. Pollox was inconsolable when Castor was killed in battle and asked his father to make his brother immortal. Zeus granted his request and as a tribute, Castor and Pollux was represented in the night sky as being reunited, joining hands in brotherly love.

Geminid Meteor Shower

Geminid Meteor shower star map

The Geminid meteor shower is a wonderful pre-Christmas treat, from when darkness falls on 13th December, peaking at 2am on Friday 14th December. It radiates from the two stars Castor and Pollux in the constellation of Gemini and the waxing crescent Moon shouldn’t pose too much of a problem as it sets at 9.30pm. White and bright, this plentiful shower rivals the summer Perseids and you should be able to spot 50 or more meteors per hour. Remember to wrap up warm; you won’t need any optical equipment, unless you want to use binoculars to study other features in the sky. 

Christmas Tree Cluster NGC2264 (Credit: ESO)

Christmas Tree Cluster

This cluster is high in the sky during the month of December at the foot of the Constellation of Gemini, which makes it a very fitting object for the Christmas season! It can be seen with the unaided eye in a dark sky.

Through binoculars, you should be able to make out an upside-down triangle shape of stars. Through small telescopes, the Christmas tree shape becomes even more apparent. The brightest star, 15 Mon, represents the base of the tree.

If you view this on a dark sky, you might be able to discern some ghostly mist called nebulosity around the cluster. Its proper official designation, NGC2264, also includes the Cone Nebula, which crowns the top of the Christmas Tree Cluster and can only be seen through telescopes of 10 inches of aperture and larger.

Mars and Neptune

Mars and Neptune conjunction
There is an opportunity to view two planets in close formation this month, especially a very far off planet which is normally difficult to find. Mars and Neptune will be in conjunction on 7th December as they emerge into the darkening sky. Look out for them when the sky darkens – blue Neptune will lie at the 4 o’ clock position to red Mars at around 0.2 degrees of separation, if viewed through steady binoculars – Neptune will appear as a faint star.
Closeup of Mars and Neptune conjunction

The conjunction makes it easy for stargazers to find Neptune if they haven’t seen it before. Through small telescopes from 4 inches of aperture, a blue disk can be observed and at low magnification, both planets will fit into the field of view. Gas giant Neptune is the furthest Solar System planet, at 4.5 billion km away and takes 165 years to orbit the Sun!

The planet Venus rises 4.10am from the beginning of month. Look out for the ‘bright morning star’ on those dark mornings, especially as it waxes from the middle of the month onwards.

The New Moon falls on 7th December and the Full Moon on 22nd December.

With Christmas drawing near, the Elan Valley Dark Skies team would like to wish you happiness this holiday season and throughout the coming year - and most of all, clear skies!