The long and dark nights of December feature some spectacular and easy to spot treats for the stargazer. In our regular guide to the night sky, Martina Redpath tells us all about the  celestial wonders of December 2010’s night sky.

As the year draws to a close, preparation for the festive season is upon us, presents are being bought and wrapped, decorations are up, Santa is checking his list twice, belt buckles are being loosened after perhaps one too many mince pies and I’m sure we have all heard Noddy Holder yelling “It’s Christmas!” one too many times? The month also brings with it fantastic sights in the night sky.  Just remember to wrap up very warm before heading outside because temperatures can drop very sharply after sunset.

This month Jupiter the largest of all planets, remains visible in the sky after sunset, not setting until after 11pm.  On the evening of 12and 13 December the bright star-like object close to the Moon will be this gas giant planet. The planets Mars and Mercury will set after 4pm around sunset in the south west  in the beginning of the month making it difficult to view both planets however, after 24 December, Mercury will rise in the south east in the morning at around 7.30 am but it will still remain pretty difficult to spot.

Also this month Venus and Saturn are visible in the pre-dawn morning. From the middle of the month both planets will be visible by 6am. Sunrise this month is around 8am giving you plenty of time to look for these planets perhaps when defrosting the car before leaving in morning? If you look in a south easterly direction Venus shines brightly with magnitude -4.9 and Saturn is also visible with magnitude +0.9 (the lower the magnitude figure is the brighter the object).  So this month Venus shines brightly and will be the brightest object in the morning sky other than the Sun and the Moon.

This month also marks the winter solstice or the shortest day of the year in the Northern Hemisphere and the longest day of the year in the Southern Hemisphere on December 21st.  This marks the point that the days will start to get longer and the nights shorter. It marks the first day of winter, however I’m sure for a lot of us it has felt very wintery already lately.

A Total Lunar eclipse also occurs on the day. For us here in Northern Ireland, the total eclipse will begin in the morning at 07.41 and last until 08.53 (GMT). So unfortunately the Moon will have set and the Sun will have risen before the entire eclipse has occurred.  Observers in the United States however will be able to see the eclipse in its entirety. A lunar eclipse occurs when there is a full Moon and the Earth is in between the Sun and the Moon. During a lunar eclipse the Moon seems to change to a bronze- red colour. As the Moon falls into the Earth’s shadow only some sunlight reaches the surface of the Moon. Any blue light is filtered out by the Earth’s atmosphere leaving the red light waves to pass through turning the Moon crimson.

Rising this month is the great winter constellation of Orion the Hunter who will remain in our night sky through until March. This constellation is pretty easy to pick out in the night sky as it contains many bright stars. If you face in a south easterly direction around 11pm this month you will be able to see Orion rising. This constellation has three bright stars in a short diagonal line marking his belt, then two stars marking his shoulders above the belt and two stars marking the feet of Orion.  The belt of Orion is an asterism,  a familiar group of stars in the sky, not a constellation alone but may form part of a constellation. The Plough is another example of an asterism in the northern sky, part of the constellation Ursa Major but not a constellation by itself.

In Greek mythology one version of the story is that Orion was a mighty hunter who boasted about his prowess and how he was the greatest of hunters. As a punishment Mother Earth sent a scorpion that stung and defeated Orion.  In the night sky as Orion the Hunter sets in the sky, Scorpio the Scorpion rises, opposite one another like the great rivals that they are. However, another version of the story is that Orion and Artemis (the goddess of hunting) where in love much to her brother Apollo’s dismay. Apollo one day challenged her to test her skills by shooting something in the distance which turned out to be Orion swimming in the sea. As part of her grieving, she placed him up into the heavens.

As well as containing many bright stars Orion also is a brilliant constellation to look at stars of varying colours. The star marking Orion’s left shoulder is a red giant star called Belteguese. Viewing with the naked eye you should be able to see that it is red in colour. This star is about 620 light years away from us and shines with a magnitude of 0.8.  Moving down to Orion’s right foot is a very bright star of magnitude 0.1 called Rigel which is much bluer in colour located about 800 light years away. Again this is visible just with the naked eye. Rigel is a huge star and actually one of the brightest in the galaxy. When compared to the Sun it is around 50,000 times brighter than our star the Sun!

Image of Orion nebula

The birthplace of future suns? The Orion Nebula, M42, as captured by the Hubble Space Telescope. (Image credit: NASA, ESA, T. Megeath and M. Robberto)

A very well-known nebula is located in the sword of Orion which hangs down from Orion’s belt, the M42 or the Orion Nebula. In this nebula new stars are being born and it is the closest star forming region to us on Earth. It was described by astronomer William Hershel (1738-1822) as ‘the chaotic material of future Suns’. It has a magnitude of 4.0 and can be seen with the naked eye however only through a telescope the beauty of the nebula can really be appreciated.

Hope you enjoy stargazing this month and have a Merry Christmas and have a Happy New Year.

Image of_Martina redpath

Martina Redpath, ESO (Image credit: Armagh Planetarium)

By Martina Redpath, Education Support Officer

1 Comment

Tweets that mention Wonders of the December Sky | Astronotes -- · December 14, 2010 at 13:34

[…] This post was mentioned on Twitter by Nat'l Museum Ireland, Armagh Planetarium. Armagh Planetarium said: What's up this month? Our regular sky guide looks at the December night sky. […]

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