The partially eclipsed Moon rising
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reDiscover the night sky

December

At a glance

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.

When it's dark and when it is not

Plan for your stargazing in advance!

Know your sunset /sunrise and moonset / moonrise times and if something cool happens while you’re out stargazing. 

The Sun

From 5AM to 9PM

The Sun is is transiting the star sign of Scorpius from 24th of November to 30th of November, then Ophiuchus until December 18 and then Sagittarius until the end of the month. 

Sunrise: 5:42 AM on the first day of December, then 5:41 for 13 days (3-15 Dec) and 5:50 on 31st of December. 

Sunset: 20:37 on 1st of December and 20:56 on December 31st. This month we have the Summer Solstice or December Solstice on Wednesday, 22 December 2021, at 04:59 in Wellington. This day is 5 hours, 58 minutes longer than the June Solstice.

In locations south of Equator, the longest day of the year is around this date.

 

The Moon

For stargazing, you must know what phase of the Moon it is. The Moon makes light pollution which washes out most deep sky objects so what you can see through a telescope when the Moon is in the sky is different than when the Moon is not.

Myth

The Moon looks bigger at moonrise because is somehow closer to the observer.

No. Our brain makes the Moon look big. The big moon is an illusion that is created by our brain. Even the astronauts in space see it bigger and nobody knows why the Moon illusion happens.

Read here NASA’s article: The Moon Illusion: Why Does the Moon Look So Big Sometimes?

Cool stuff to see this month

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 (all 4.5 hours of astronomical night) 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.

Due East – Taurus Orion region

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. 

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.

To the North you can also observe the Pleiades and the Hyades.

“A philosopher once asked, “Are we human because we gaze at the stars, or do we gaze at them because we are human?” Pointless, really…”Do the stars gaze back?” Now, that’s a question.”
― Neil Gaiman, Stardust

Grus – the Grus Quartet of galaxies is in a very good position to observe and the constellation is spectacular in itself due to the line up of naked-eye double stars that makes a beautiful row in the sky.

Read about Grus on wikipedia.

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 Sam 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.

When we are not doing stargazing with the public or with our own telescopes, we turn to SLOOH to explore the Universe. If you are really passionate about astronomy, want to learn more or just expand your knowledge, SLOOH is the next level. See you there, make sure you join the Star Safari club and say hi. 

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What is SLOOH?

Patented technology to explore space.  Robotic, mountaintop, online telescopes, live 18+ hours per day.

Curated journey of discovery. Space is a vast wilderness and Slooh is like a national park, with trails and guides. 

Communal exploration of the Universe. Learn from fellow members using the telescopes.

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