The Sky of December

Featured image by Alex Conu, 15 December map, 23:00 hrs.

The stars …

December in the Southern Hemisphere is generally the unhappy month for the astronomer, unless your thing is solar astronomy, because the nights are short and the temperatures are creeping up. It’s seems to take forever for the night to get truely dark and forever for the telescope to cool down. Unlike the rest of the population, us astronomers are craving a cold front to blow through and give us a nice cool patch of air to settle the thermals and give us some great seeing. The good news is that this time of year is perfect for an all nighter of astronomy as the Milky Way passes through the zenith in the early hours and there’s a wealth of deep sky objects to fill your eye piece.

A good place to start an evening’s viewing is Orion, that majestic constellation that is easy to find in the Northeast at about 35 degrees in elevation. With a pair of binoculars an observer can easily see the Great Orion Nebula (Messier 42 or M42) which is a huge star forming region just above Orion’s Belt, which is made up of the three stars of Alnitak, Alnilam and Mintaka. Mintaka is very dear to navigators as it’s located exactly on the celestial equator. M42 is relatively close to us at about 1400 light years which makes it one of the brightest nebulae in the sky. With a telescope the M42 can appear to have a greenish tint, unlike the bright red photos that are often published. It is estimated that M42 is about 24 light years across and that it is part of a much larger structure known as the Orion Molecular Cloud, which extends for about 10 degrees across the whole constellation of Orion. This cloud includes the famous Horse Head Nebula (B33), Flame Nebula (NGC 2024), M78 and Barnards Loop (Sharpless 2-276). Below is a photo I took of M42 a few years ago, it’s one of the most photographed objects due to its brightness and visibility in both the Northern and Southern Hemispheres.

M42, Great Orion Nebula

Orion has a number of very interesting stars including Betelgeuse which is a red supergiant and one of the largest stars in the sky. It is one of the few stars that have been imaged and it’s unusual shape is quite apparent showing is probably has a very unstable atmosphere causing the asymmetric bulging of the star. Because of its massive size Betelgeuse will not live for much longer – maybe only another 1000 years. Or it may have already exploded! But given its 400 or so light years away we might not find out for a while. When it does go it will create quite a spectacle on Earth as it will be a very bright supernova and will probably even be visible in daylight.

Check here in the sky in December 2017 – a post that talks about planets and other ephemeral things…

Clear skies!