In December, we experience the shortest nights in the Southern Hemisphere. Throughout December, the Sun sets from about 8:30 to 9pm and rises about 10 to 20 minutes before 6am. The real night (astronomical night) only lasts about 4.5 hours. At sunset, the skyscape is marked by the stars of Orion and the Magellanic Clouds that are now high in the sky. The Galactic centre is gone beyond the horizon, it would be visible before sunrise from next month.
A favourite asterism this time of the year is the Great Square of Pegasus – the only horse that looks like a square.
Pegasus – photo by John Drummond 2006 for MataOra[/caption]
The horse pulls a sleigh – made of the Pleiades, Hyades and Orion. Sorry, we don’t have reindeers in New Zealand.
Running behind the sleigh, on the ground , is a Dog (Sirius). The sleigh has just come up from behind the greatest Christmas tree, standing tall in the south. Unbeknownst to the dog, a cat (Canopus) who was hiding in the tree jumps to catch the back of the sleigh. You can see it half way through the sky, about to land on the dog.
In the south, just after sunset, Achernar, the Magellanic Clouds and the Southern Cross look like a Christmas tree. Achernar is the star on top of it, the Magellanic Clouds are like patches of snow on the tree and at the base, the Southern Cross is the trunk. All the other stars in Centaurus and Vela are the Christmas Tree decorations on the lower branches. We might not have snow this time of the year in the Southern Hemisphere but is like nature compensated for that with a celestial Christmas Tree just in time for Christmas.
If you draw a line from Sirius to Canopus – which are two very bright stars, it will lead you to the Magellanic Clouds.
Sirius is in fact the brightest star in the sky, Canopus is the second brightest star in the sky and to the right of the imaginary Christmas Tree is Alpha Centauri, the third brightest star in the sky.
Lower on the Northern horizon, underneath the galloping hind-legs of the horse, Andromeda Galaxy is a smidge of light. It is the furthest object we can see with the naked eye at 2.5 million light years distance from us. When the light that we see now from Andromeda left the galaxy, on Earth, some of our hominid ancestors, facing food shortages, developed larger brains, as an evolutionary strategy. This led to the genus Homo, which first arose 2.5 million years ago. Homo habilis developed as the ice ages begun (periods of repeated glaciation), a time known as Pleistocene. And who knows, maybe the first human memories of winter too.
From the wisdom book of the stargazer:
If you wish to become a serious stargazer, first, you need a pair of binoculars. We recommend getting binoculars before buying a telescope. We love using them, plus, when stargazing with binoculars you use both eyes. There’s nothing like using both your eyes to see faint objects.
What’s out there
Some cool binocular objects this month lay low around the horizon. Double Stars (Alpha Centauri, Gamma Velorum, Beta Muscae and Upsilon Carinae, The Pleiades and Andromeda Galaxy are all great binocular targets.
The Moon and the Planets however are easier to observe.
Then, of course, the Magellanic Clouds are great to look at.
Some favourites of ours are visible in the night sky in December. The first of these is M74 which is vey hard to see due to its very low surface brightness. With very dark skies it can be seen from the Wairarapa. Luckily it’s not all bad for galaxy hunting in December as not too far from M74 is the bright galaxy of M77 – also known as Cetus A. This one is easy to spot even from central Wellington. We won’t see the faint outer regions of the spiral arms but the bright active core is very visible and at 33 Million light years distant the photons from this object have spent a long time making their way to Wellington.
We do have some very impressive galaxies in the Southern Sky. One of these is NGC 253 – also known as the Sculptor Galaxy. This is large spiral galaxy at an angle to us so it looks like an elongated ellipse. It’s relatively bright and easy to spot it you’ve got plenty of aperture. You’ll have to put your light bucket on the back of your scooter and head to a dark sky location to make out much detail, but if you do, you’ll be in for a treat as you take in the complex shapes and clumps of detail visible on the disk. Sculptor is about 12 million light years away appears about 27 arc minutes long so is quite big.
Quite close to Sculptor is the tight spiral galaxy known as NGC 300. This is a great galaxy to view as it’s quite close at only 6.6 million light years – for Northern Sky observers it’s a bit like a mini M33. Viewing from Wellington will show the bright core but you’ll have to head to the hills to get any detail out of the spiral arms. Keen astrophotographers will have a better time in Wellington as this galaxy is bright enough to burn through the light pollution and produce quite a nice picture.
The problem with viewing galaxies is that they don’t really look anything like the beautiful photographs people take. They are often just a faint grey smudge in the eyepiece and you have to use your best visual observing skills to get any detail out of what you’re looking at. This is when it’s great to swing the telescope around to the majestic brilliance of the likes of the Tarantula Nebula. This gives you a picture in the eyepiece very similar to what photographers capture, just not in colour. This big giant bright complex of gas clouds and massive stars looks a bit like a spider, hence its name and it is a must see of the Southern Sky and is almost compulsory viewing on any observing evening.
At this time of the year the two galaxies groups of the Fornax Cluster and the Grus Quartet are also in a good position for viewing. As the month advances the position of the Fornax Cluster improves and the position of the Grus Quartet gets worse so get in early to see these four stunning galaxies. Both groups are between 60 Mly and 80 Mly distant with the Grus Quartet being three galaxies visually quite close to each other and another galaxy a little further away. With the right eyepiece you can get all four in the same field of view. With the Fornax Cluster is is possible to get up to 11 galaxies at once in the same field of view. These are mainly elliptical galaxies including the stunning Fornax A.