Looking to the Skies December 2021 By Brian Davidson

I hope you managed to see the planets Venus, Saturn and Jupiter all in a line just after sunset on one of our clear nights. On Sunday 28th November I spotted Venus bright in the sky just as the sun was setting from my armchair in my lounge! I did have to get up off my bottom to spot the other two as the skies darkened although Jupiter is so bright that you cannot miss it either.
 
Observing
The following chart represents the night sky at 11.00pm GMT on the 8th of December and at 10.00pm GMT on the 23rd December. To use the chart, face south at the appropriate time with the bottom of the chart towards the southern horizon and you will see the stars in the chart. If you are observing a little earlier in the evening then the view is shifted 15 degrees eastwards for every hour before the specified time.

This month the focus is on the constellation Orion- The Hunter. It’s my favourite constellation because of its distinctive shape and because it appears to have everything. It doesn’t take much to visualise a hunter from the stars in Orion and what stars they are! Orion’s right shoulder is represented by the star Betelgeuse,  a variable red supergiant, varying in magnitude from about 0.3 to 1.2 and the 7th brightest star in the northern hemisphere. If Betelgeuse were to replace our sun it would reach out all the way to the orbit of Jupiter. It also has the potential of going supernova but of course we do not know exactly when. Then, representing his left foot, is the blue supergiant Rigel the 5th brightest star in the northern hemisphere with a magnitude of 0.2. Between these stars is a line of three stars going from south east to north west and they represent Orion’s belt and at magnitudes of around 2 they are unmistakable. Less bright but still visible to the unaided eye is Orion’s sword hanging from his belt. The bottom star of the sword should be visible in good conditions and above this is a misty fuzzy patch which is the Orion nebula (aka M42) where star formation takes place. Try to observe it through binoculars or a telescope if you get the chance.
The rest of this blog is about stars and there will be more to say about the constellations in which they lie next month. Because it is so easily recognisable, Orion is a good starting point for finding your way about the night sky during the winter months and especially for the stars we discussed last month. Follow a line from Orion’s belt to the upper right, underneath the star Bellatrix representing his left shoulder, and you will find the star Aldebaran, a giant red star of magnitude 1 and the 9th brightest star in the northern hemisphere. Continue the line beyond Aldebaran and you find the star cluster- The Pleiades or Seven Sisters.
 Having followed the line to the Pleiades turn ninety degrees to the north and the bright star you see is Capella, in the constellation Auriga- The Charioteer, lying directly above Taurus. It is the 4th brightest star visible in the northern hemisphere and shines at magnitude 0.1.
Now follow a line from Orion’s belt to the south east and you will find the brightest star visible in the night sky, Sirius- the Dog Star. At magnitude -1.4 it is twenty three times more luminous than the Sun and a mere 8.6 light years distant. Sirius is part of the asterism known as the Winter Triangle, formed in conjunction with Betelgeuse and Procyon which lies due east of Betelgeuse. The white star, Procyon, is the 6th brightest star visible from the northern hemisphere so it is little wonder that the Winter Triangle is something to behold. It is outlined in yellow in the chart.
We finish this month with another asterism- the Winter Hexagon. It is roughly centred on Betelgeuse and comprises the stars Procyon, Sirius (both in the Winter Triangle), then continuing anti-clockwise, Rigel, Aldebaran, Capella and Pollux. It is outlined in red on the chart. You can enjoy viewing all these throughout the coming winter months as they make their way westwards in the evening sky.
 
Something to look out for
            A solar eclipse takes place on Saturday 4th December but unfortunately it will not be visible from Europe. Look out for coverage in the media because it is always good to see.
            Having witnessed the planets aligned last month there is a chance to see each one in turn, Venus, Saturn and Jupiter have a close approach with the Moon on the 7th, 8th and 9th of the month respectively.
            Finally the December solstice is on the 21st.
Clear skies.