Much of this month’s view is taken up by the constellations visible in January – Orion, Taurus and Auriga. See the January item for more on these. This month, you can see that the great hunter Orion is followed through the sky by his two dogs, Canis Major and Canis Minor. You don’t need to know much Latin to work out that these names mean Greater Dog and Lesser Dog.
Remember that as the sky moves from left to right, these two dogs will faithfully follow Orion night by night throughout the winter and spring months.
The main star of Canis Major is Sirius, which is the brightest star in the night sky. (We have to say night sky to prevent know-alls pointing out that the Sun is a star so it’s the brightest!) From our northerly latitudes it appears fairly low down, so it can be strongly affected by twinkling, which in such a bright star can make it look as if it’s shooting out coloured rays. It has even been reported as a UFO for this reason! It may not be a welcome astronomical phenomenon, but on a clear frosty night when the stars are sparkling and twinkling like mad, it’s a lovely sight.
To the left of Orion is another bright star, Procyon, the main star of the Lesser Dog, Canis Minor. And above that are two stars, Castor and Pollux, which mark the heads of the Twins, Gemini. The bodies of the Twins are two lines of stars which extend towards Orion. If there are any bright planets around they will be in the region of sky from Gemini to Taurus, as this is where the line of the Zodiac runs.
Looking north
Most of the constellations in the northern sky are always to be seen in this direction – it’s just their orientation that changes from month to month. Look for the seven stars of the Plough, up in the north-east, and the W-shape of Cassiopeia, high up in the north-west at this time of year. The Plough is known as the Big Dipper in North America. Use its two right-hand stars to point towards the Pole Star, Polaris, which is always in the same position in the sky. Once you’ve found it, you can use it to get your bearings on any night, though all the other northern constellations wheel around it anticlockwise.
Polaris is a second-magnitude star, about the same as the stars in the Plough or Cassiopeia, so don’t expect anything particularly bright. It’s just by chance that this millennium it happens to be very close to the pole of the sky, but there is a slow movement of the sky over the centuries that shifts the position of the stars, and 1000 years ago it wasn’t as close as it is now.
Capella, at the top of this map, is also shown at the top of the south-facing map, as it’s virtually overhead. If you have a clear northern horizon you might be able to see Vega as well low down. These stars are two of the brightest in the sky, and while Capella is overhead in winter, Vega is overhead in summer.
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