The dog star ‘Sirius’ is now high and visible in winter skies looking South. Draw a line down and left from Orion’s belt and you can’t miss the brightest star in the night sky.
Sirius means ‘scorching’ and was considered a second Sun of sorts to many ancient cultures. Its incredible brightness is due to its close proximity. At only 9 light years away it’s the 5th closest star system to our Sun and a fairly typical hydrogen fusing main sequence star likely to live a long stable life of several billion years. This is in contrast to short lived giant stars like Rigel and Betelgeuse, which are very distant and appear bright due to their bloated sizes and massive energy output.
Procyon is sometimes mistaken for Sirius but it rises earlier, hence its name which means ‘before the dog’. The Arabs told a tale linking Procyon and Sirius as two sisters, who became separated by a great river (the Milky Way) while searching for their missing brother.
You can see three excellent examples of open star clusters within the Orion and Taurus constellations, all in one convenient direction during winter skies (looking south or south east) and in a rough line drawn out by Orion’s belt.
Start with the Orion nebula (M42), below the three belt stars in Orion. This star forming region contains a very young open cluster called the Trapezium which is surrounded by glowing clouds of ionised hydrogen gas. You can see this nebula in binoculars but it looks best in a low or medium power telescope eyepiece.
Moving up into the eye of Taurus to the red giant star Aldebaran, we find the Hyades cluster. Aldebaran is like a premonition of the fate that awaits out own sun. A red giant around 7 billion years old, bloated and shuddering in its final gasps before it collapses down to a white dwarf. Shining brightly all around Aldebaran are the members of the Hyades open cluster (although they are much further away) – quite a mature cluster at around 500 millions years old. Best viewed in binoculars.
And finally moving higher and to the right we find the Pleiades, a lovely jewel box of middle age hot stars (and many less bright members) slowly drifting apart to join the general distribution of stars. When the dinosaurs roamed the earth this cluster would have resembled the Orion nebula – bright and nebulous, its hot infant stars lighting up the surrounding hydrogen gas clouds.
The Seven Sisters
The lovely Pleiades star cluster (Seven Sisters) is becoming a viable late night stargazing target for observers in northern Europe again. Look up in the East after 11pm to see the distinct jewel like arrangement of stars. Note the red supergiant Aldebaran (Abarbic for “The Follower”) trailing just behind and to the left. Pick out a pair of binoculars to see the Pleiades at their best – telescopes reduce the field of view too much for objects like this.
The Pleiades is an excellent example of an open cluster. These are relatively younger energetic stars still in close proximity to their siblings having all emerged from the same region of intestellar dust and gas. Eventually these stars will move apart and join the general distribution of more widely dispersed stars.
If you’re awake after that, the hunter Orion will begin rising from the East around 1am. Grab your binos again and marvel at the star forming emmission nebula below the main three stars in the belt. This is an active star forming region over 1000 light years away, where new stars are being born from dense clouds of hydrogen. Train a telescope at moderate magnification on the Orion nebula and you’ll be blow away by the majesty of the extended dust clouds, energised and glowing due to the nearby influence of young hot stars.
The Orion Nebula
Planet wise, Neptune and Uranus can be observed almost all evening after darkness, but you’ll need a reasonably powerful telescope to resolve them as tiny blue-green disks.
All the best and clear skies!