Night Sky December 2018
To use the star chart: print it out and then use it to locate the planets and constellations at night by holding it above your head and pointing the 'South' pointer of the chart southwards.
Ian Morison tells us what we can see in the Northern Hemisphere night sky during December 2018.
- Jupiter - Jupiter passed behind the Sun on November 26th and will appear low in the eastern pre-dawn sky around the 12th of the month. It will have a magnitude of ~-1.8 and a disk ~32 arc seconds across. It is not a good month to observe Jupiter due to its low elevation, but do see the 'highlight' above.
- Saturn - Saturn might just be glimpsed in the first few days of December very low in the southwest around 16:45 but soon disappears into the Sun's glare as it moves towards superior conjunction on January 2nd. It will have a disk of ~15 arc seconds and a magnitude of +0.5.
- Mercury - Mercury passed between us and the Sun (inferior conjunction) on the 27th of November but appears in the pre-dawn sky around the 6th of the month. It will then have a magnitude of +0.5 which increases to magnitude 0 by the 8th. Mercury reaches its greatest elongation (west) of the Sun on the 16th, when 21 degrees away and rising over an hour and a half before it when it is ~60% lit. As the morning ecliptic is at a steep angle to the horizon at this time of the year, this is an excellent apparition. Do not miss (when hopefully clear) its conjunction with Jupiter as described above.
- Mars - Mars, though fading from magnitude -0.0 to +0.4 during the month remains prominent in the southern sky as it starts the month at an elevation of 27 degrees in Aquarius. It will lie due south around 6 pm. As the month progresses, it moves eastwards into Pisces on the 21st; slightly higher in elevation at ~32 degrees when due south around 5:30 pm. Its angular size falls from 9.3 arc seconds to 7.5 arc seconds during the month so it will become harder to spot any details, such as Syrtis Major, on its salmon-pink surface.
- Venus - Venus begins December at an elevation of ~32 degrees and with a dazzling magnitude of -4.9. Its angular size reduces from 40.7 to 26.6 arc seconds during the month as it moves away from the Earth but, at the same time, the percentage illuminated disk (its phase) increases from 26% to 47% - which is why the brightness only reduces from -4.9 to -4.6 magnitudes. It will reach greatest elongation from the Sun on January 6th.
- Comet46P/Wirtanen rises high in the sky and may be visible to the unaided eye. This month we have a chance of seeing a comet with our unaided eyes as it could reach magnitude +3. The chart shows its position during the month as it rises above the southern horizon through Taurus and Auriga. On the night of the 16/17th December it will pass between the Pleaides and Hyades clusters in Taurus - making a wonderful imaging opportunity if clear. Then, on the night of the 24th, it will lie very close to Capella in Auriga (but sadly, the Moon will then be full).
- December 3rd - before dawn: Venus below a very thin crescent Moon. Looking southeast before dawn one should, if clear, be able to easily spot brilliant Venus lying below a very thin crescent Moon. Spica is over to the right of Venus making a nice photo opportunity.
- December 7th - 1 hour after sunset: A very close conjunction of Mars and Neptune. Looking south after sunset one should, if clear, be easily able to spot Mars. But when it gets fully dark, with binoculars or a small telescope, Neptune should appear just down to its lower right. A great opportunity to find Neptune - let's hope it is clear!
- December 14th - after sunset: Mars will lie 4 degrees above the First Quarter Moon. Looking south after sunset one should, if clear, be able to spot Mars lying about 4 degrees above the First Quarter Moon making a nice photo opportunity.
- December 14th and 15th after midnight: the Geminid Meteor Shower. The early mornings of December 14th and 15th will give us the chance, if clear, of observing the peak of the Geminid meteor shower. The Moon is at First Quarter and will set around 11 pm so, when Gemini is highest in the sky, its light will not hinder our view. The Geminids can often produce near-fireballs and so the shower is well worth observing if it is clear. An observing location well away from towns or cities will pay dividends. The relatively slow moving meteors arise from debris released from the asteroid 3200 Phaethon. This is unusual, as most meteor showers come from comets. The radiant - where the meteors appear to come from - is close to the bright star Castor in the constellation Gemini as shown on the chart. If it is clear it will be cold - so wrap up well, wear a woolly hat and have some hot drinks with you.
- December 21st - just before dawn: Jupiter and Mercury together with Venus above. If clear just before dawn, and given a low horizon towards the east, one should be able to see Mercury lying a little above Jupiter making it appearance in a new apparition. Venus will be shining brightly up to their right. A nice photo opportunity.
- December 22nd/23rd - late evenings: the Ursid Meteor Shower. The late evenings of the 22nd and 23rd of December are when the Ursid meteor shower will be at its best - though the peak rate of ~10-15 meteors per hour is not that great. Sadly, this year Full Moon is on the 21st, so its light will greatly hinder our view. The radiant lies close to the star Kochab in Ursa Minor (hence their name), so look northwards at a high elevation. Occasionally, there can be a far higher rate so it is worth having a look should it be clear.
- December 16th (late night) and 17th: Two Great Lunar Craters. This is a great night to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby. Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old. It is interesting in that it is thought to have been formed by the impact of one of the remnents of an asteroid that gave rise to the asteroid Baptistina. Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago. It has a diameter of 85 km and is nearly 5 km deep. At full Moon - seen in the image below - the rays of material that were ejected when it was formed can be see arcing across the surface. Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains. It is 93 km wide and nearly 4 km deep and is a clasic "terraced" crater. Both can be seen with binoculars.
Haritina Mogosanu from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during December 2018.
Also on display is a James Short telescope. We only look at this one - and not through, it's locked in the displays. It's a very important telescope that we believe came here with Captain Cook and it was donated by Adam Read; he is the son of Peter Read, the creator and presenter of the New Zealand's Night Sky TV show in the 1960s.
We also have a beautiful planetarium where I spend a lot of my time.
If you ever wish to find us, Space Place is at the top of the botanical gardens looking out to the harbour, and surrounded by flowers and New Zealand birds that are amazing so you can imagine the views, and the sound, both day and night. We actually have a bunch of New Zealand owls in a tree right in the front of us, they are called morepork and we can always hear them when we look through the telescopes.
And did you know that this Christmas we celebrate 50 years since we went around the Moon? Also in December, the Americans are aiming to land a probe on an asteroid to get a sample and, - my favourite - someone calculated all the starlight that adds up in the Universe, so starting this month we will be fully informed about how many photons are reaching Earth, since the dawn of time, or so they say.
So a comet-party seems like a good idea. The best time to look at it is just after sunset and on the 16th of December will have the magnitude of approximately 3. What does that mean? It means we can see it with the naked eye.
Have you ever tried to pronounce a comet's name? 46/P Wirtanen (go pronounce that in one word!) P stands for periodic and 46 is that it's the 46th to be discovered (in case you were wondering, the first ever was Halley's comet). Wirtanen will arrive from the direction of Cetus / Eridani and is very tiny. Only 1.2 km in diameter, Wirtanen has a short period too, 5.4 years.
What's cool is that this comet was the original target for ESA's Rosetta spacecraft but the launch window was missed so they sent the probe to another comet with an even better name (just because is longer and harder to pronounce) 67P/Churyumov-Gerasimenko.
What's a magnitude 3? If you ever managed to spot the famous galaxy Andromeda, then you have the answer. Something that looks like Andromeda (3.4).
Now that you know where to look, and what you might find, the comet can be your centrepiece for the comet-party. But nothing says that you should not look at the stars and deep sky objects.
Some favorites of mine are visible in the night sky and the early part of the month will be ideal to try and see them given the Moon will be well hidden. The first of these is M74 and unfortunately, despite all of the aperture we have available at Space Place, we are not going to see this one visually because of it's very low surface brightness. We'll have to borrow the van and take the portable Meade over the hill to the very dark skies of the Wairarapa to see this beautiful face on spiral. 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.
Despite not having M51 and M101 to look at, 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 arcminutes 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 gray 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.
We wish you happy hunting for comets and galaxies this month, and if all that doesn't work then grab yourself a couple of craters on the Moon.
Provided courtesy of: http://www.jodcast.net/