Podcaster: Ralph & Paul
Title : Awesome Astronomy’s December Sky Guide
Organization: Awesome Astronomy
Link : www.awesomeastronomy.com
Description: What to look out, and up, for in December.
For the beginners this month we take a look at the constellation of Gemini with bright star Castor providing a nice easy double star to split with a telescope. We move over to the feet of the Gemini twins to scan for some nice open clusters, including Messier 35, before hunting down the beautiful Eskimo planetary nebula. Finally, we go looking for a star known to have a planet of its own.
Next we round up the planets that are visible in December: Jupiter, Venus & Mars are still around for observers after midnight and we have the possibility of a naked eye visible comet in the early hours of the morning in early December as C2013 US10 Catalina raises northern hemisphere hopes.
We have the Geminid meteor shower peaking on the night of the 12/14th December – which always puts on a great show and then we take you on a tour of the often overlooked deep sky objects in our winter skies around the constellations of Orion, Lepus and Eridanus.
For those in the Southern Hemisphere, 365 Days of Astronomy also play Alice Enevoldsen’s What’s Up Tonight, Southern Skies Edition each month.
Bio: Awesome Astronomy is the show for anyone and everyone who has even the slightest interest in astronomy and science.
Join Ralph & Paul twice each month, for informative and fun astronomy programs telling you what to look out (and up) for every month. You can be guaranteed a passion for astronomy, simple explanations of complex and fundamental topics, space and science news, absorbing interviews with astronomers who make the news and listeners’ astronomy questions answered
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Transcript:
Paul: December for astronomers means three things, new kit, the longest darkest nights and new socks… and all are very welcome! It is a month to get out and wrap up warm to take advantage of those long nights and of course the winter sky is one of the most spectacular of the year. But before we look at what the solar system is giving us and our deep sky tour, what has Ralph lined up for our beginners guide?
Ralph: Well, in December we welcome back the Gemini twins. We’ve got an easy binary star, an open cluster, a faint planetary nebula and a bit of exoplanet hunting to finish with in Gemini.
Firstly, you’ll want to find the shape of the two twins Castor and Pollux (that’s Pollux) which are also the names of the brightest two stars in the constellation that sit at the head of the twins. Pollux is the lower one of the two, with Castor looking slightly dimmer immediately above it. And by the end of the month they’ll be high up in the south around midnight.
Our first stop is Castor which is actually a quadruple star system but we can only easily resolve it into two stars. With a modest 60x magnification a small scope will easily split Castor into the two white stars that sit 50 light years away orbiting around their centre of gravity every 450 years or so.
Next up we go to the far end of Gemini and the outstretched leg of Castor. Actually, there’s a line of 4 open clusters all within 2 degrees of each other here, just above the highest foot. But we’re interested in the brightest cluster that appears to be sitting on top of castor’s foot. This is Messier 35 or NGC 2168 and at magnitude 5 you might just be able to see it with the naked eye in dark skies and it’s a favourite with binocular viewers. But just a little extra magnification will show the tendrils of stars that seem to emanate from a dark void in the centre. But do trace the line back down to 1 Geminorum in the foot and see how many of the 4 open clusters you can bag.
Next up is more of a challenge and I’d recommend at least a 5” scope for this. If you draw line from the star in the waist of the Castor, through to Wasat in the waist of Pollux, then extend this line for two more degrees or the width of two fingers held at arm’s length. This should find you in the right spot for the Eskimo Nebula NGC 2392. Although a faint smudge in small scopes, a larger aperture will show you the iconic face inside a Parka hood that gives this planetary nebula its name. At almost 3,000 light years away William Herschel was still able to spot this magnitude 10 fuzzy star, which we now know is shells of gas that are energised by the star in the centre.
Finally we go exogazing. We can’t spot exoplanets with amateur telescopes but we can take a look at their host stars and know the characteristics of the planets that orbit some of them. And in Gemini we have the exoplanet with the brightest host star, Pollux in the head of the lower twin in the sky.
Taking a look at this orange giant, you can know with some certainty that there is a gas giant planet called Pollux b orbiting a similar distance from Pollux as Mars is from our sun, but three times the size of Jupiter. And there are at least 6 other stars in Gemini that are known to play host to other planets. So back to you Paul.
Paul: The Solar system this month sees all the real action in the constellation of Virgo, which is hoarding all of this month’s solar system treasure. It is a view for the night owls but well worth staying up beyond midnight for. First we have Jupiter that rises around midnight and is once again really starting to come into it’s own, by 2.30 jupiter is joined by mars which is still pretty unimpressive in all but the largest scopes but is beginning to improve as we slowly move towards the 2016 opposition. Then before 4am the potential highlight of the season appears comet C2013 US10 Catalina. This of course has a big caveat of “it’s a comet” on it so of course may never hold to predictions, but at present we are looking at a naked eye comet, possible getting down to magnitude 4. I know, I know you’re excited, i’m excited too, but please don’t get cross if it doesn’t behave. The comet will move through the month towards Arcturus in Bootes, passing that star on new years day. To complete the set Venus gives you the finale of this solar system extravaganza, rising about 4.30. If you have the energy to do so, several early morning sessions of astronomy are probably in order through December, which if you are out and about on the 13th and 14th you will also have the added bonus of one of the great meteor showers, the Geminids.
Indeed the Geminids have a ZHR bigger than the perseids. It is perhaps less famous because of the time of year, the perseids picking the warmer less cloudy time of the year to put on their show. The radiant will move past Castor in Gemini through the month with the radiant just next to Castor at the showers peak on the 13th/14th. The best time to see the shower is in the early hours of the 14th. This should be a great year for seeing the geminids as the moon is new on the 11th so will be well out of the way for the peak. Our companion is at last quarter on the 3rd, first quarter on the 18th and full on the 25th.
For our deep sky challenge this month we are going look at objects that are in or near Orion that aren’t the habit forming M42 or flame and horsehead nebulae. The area of sky around Orion is one of the skies most famous and always eagerly anticipated, but hidden around it are perhaps some of the most overlooked deepsky objects, drowned out by the clamour for perhaps the most famous objects in the sky.
First of all let’s start with two of the most ignored Messier objects on the list. M78 is in Orion just to the left of a line from Betelgeuse and alnitak in the belt. This is an emission nebula that is also part of the orion molecular cloud and is around 1600 light years away. You will see two stars with this cloud that are around magnitude 10 and are responsible for lighting up this cloud of dust.
Next we are dropping below Orion into the rarely viewed constellation of Lepus the Hare, the poor creature being chased by Orions dogs. Below the main body of the constellation you can find Messier 79 a globular cluster, unusual for the time of year as we mainly think of globs as a summer target and also a bit of an enigma as it is thought that M79 is not native to our galaxy and may have originally formed part of the disputed canis major dwarf galaxy. It is often described as starfish shaped and is magnitude 8 and 42,000 light years away.
We will now jump to the right of Orion and look at the constellation Eridanus, the river. It is a long indistinct constellation that fills the sky in the area to the right of Rigel. Here you can track down two nice targets in the form of planetary nebula NGC1535 which is a real challenge for observer and imager alike and will need patience and good skies, but you will be rewarded with a distinctive blue fuzzy disc. To begin your hunt start at the star Zaurak and move back towards Rigel and as Zaurak leaves your finder scope you are close. Now above 1535 is a nice multiple known as Keid which has celebrity status, for this is the home star of the planet Vulcan. Keid A is in fact very similar to our sun and must be a prime target for SETI, it has two faint companions B which is easily seen in a reasonable sized scope at low power and C which is much fainter and requires high magnification and a good clear sky.
For our last around Orion challenge we go back into the constellation itself but this time to the rarely visited club, the area of stars above betelgeuse towards gemini. Here you will find The monkey head nebula NGC2174 and an associated cluster 2175. This is an Hii emission nebula 6,400 light years away and is magnitude 6.8.
So I wish you happy hunting and clear skies.
End of podcast:
365 Days of Astronomy
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