I hope you have had a chance to look at the evening sky as the Sun sets earlier and been able to pick out Mars. I’ve had some people ask me what ‘what is that bright ‘star’ in the east in the early evening?’
The following charts represent the whole night sky at 10.00pm GMT on the 8th of December and at 9.00pm GMT on the 23rd December. You will understand from this that we want to have a look at everything in the winter sky. To use the charts, face in the direction indicated by the letter at the bottom of the chart at the appropriate time and you will see the stars in the chart. If you are observing earlier in the evening just turn eastwards by 15 degrees for every hour before the stated time but objects will be lower in the sky.
You will have no problems identifying anything because we are unashamedly looking at only the clearest and brightest constellations and stars available.
So with the chart above, face your south-eastern horizon and mentally tick off the following eleven objects. We will start with my favourite constellation, Orion – The Hunter, with one of the brightest red supergiants in the sky, Betelgeuse, representing his right shoulder and Rigel, a brilliant blue-white supergiant representing his left foot. Then there is the unmistakeable asterism, Orion’s Belt, around his waist. Follow a line down from Orion’s Belt towards the horizon and slightly eastwards and you find the brightest star in our night sky, Sirius, aka the ‘Dog star’.
Now follow a line from Orion’s Belt about the same distance in the opposite direction and you should find another giant red star, Aldebaran, in the constellation Taurus- The Bull. Of course this star is currently outshone by the nearby planet Mars which is crossing the upper horn in Taurus as it continues its retrograde motion. So below and to the right hand side of Mars you should be able to pick out the red star Aldebaran if the sky is clear. A chance to spot the two together.
Continue in the same direction beyond Aldebaran and there lies a bright star cluster- The Pleiades, popularly known as the ‘Seven Sisters’. The Pleiades doesn’t form a large object in the sky but it does catch the eye.
Return to Aldebaran and on the line from Orion’s Belt turn through 90 degrees to your left and continue upwards to your zenith. The bright star you will see is Capella, a binary system consisting of two yellow giants and the 4th brightest star visible from the northern hemisphere lying in the constellation Auriga- The Charioteer.
The chart above is the same chart as before but now we are looking towards our south-western horizon. We were looking at this part of the sky earlier in the year when it was higher in the sky. You will probably have already seen it but near your zenith is the familiar shape of the constellation Cassiopeia- Queen and wife to King Cepheus in Greek mythology. We will come back to it in the final chart. To the west you can see the constellation Cygnus- The Swan, flying down the Milky Way with the bright supergiant star, Deneb, representing its tail. And further west still and nearer the horizon is the even brighter star, Vega, in the constellation Lyra- The Lyre, the third brightest star visible from the northern hemisphere. We enjoyed these in the summer months as part of the Summer Triangle but the third star Altair has dropped below the horizon.
For our final chart below we now need to face our northern horizon.
We are in very familiar territory now as close to the horizon we can readily pick out The Plough, the well known asterism in the constellation Ursa Major- The Great Bear. The two pointer stars at the top of The Plough direct us to Polaris, the pole star, at a distance of about five times the distance between the pointers. Note that Polaris is the dimmest named star in this blog. If you now follow a line from the third star in from the end of the Plough’s handle through Polaris and continue the same distance again we arrive back at Cassiopeia. It is one of my pleasures throughout the year watching The Plough and Cassiopeia rotate about Polaris in a circle and changing their orientation with the passing months.
I hope you get a chance to enjoy this trip round the winter night sky this month
Something to look out for
Mars reaches opposition on the 8th December and, excluding the Moon, is the dominant object in the night sky. Its magnitude is approaching -2.0 and at the beginning of the month reaches its highest point in the sky about midnight so it can be observed from early evening all through the night.
There will be a close approach of the full Moon with Mars on Thursday the 8th December and in fact there will be a lunar occultation with the disappearance of Mars behind the Moon at about 5.00pm GMT in the western sky with it re-appearing about an hour later. Finally, since we are concentrating on Mars this month, by the 30th December it will be north of Aldebaran and almost equidistant between that star and the Pleiades.