Adrian Dening's Stars Over Somerset

Wednesday, 22 September 2021 17:00

Monday 27th September to Sunday 3rd October 2021

Between the constellations of Cassiopeia and Perseus you will find the Double Cluster which is a pair of open star clusters that can just be seen with the naked eye from a dark location.

Stars in an open cluster are roughly all the same age as they were all originally formed from the same giant molecular cloud.

In the case of the Double Cluster, the stars are relative youngsters - only 13 million years old. Compare this to another well-known open cluster we have looked at before - the Pleiades - the stars there are between 75 to 150 million years old!

Each half of the Double Cluster consists of a few hundred stars and they are actually moving towards us at a speed of approximately 24 miles per second. Don't worry though as the clusters are 7,500 light years away and so it will be a very, very long time before they get close to us!

The Double Cluster is also known as Caldwell 14 - the Caldwell catalogue of deep sky objects was compiled for amateur astronomers by the late Sir Patrick Moore as a compliment to the Messier catalogue.

So when should you look for the Double Cluster? The simple answer is "anytime" so long as it's dark (!) because the object is circumpolar. This means that it is always above the horizon and will appear quite high in the night sky. Just find the famous "W" shape of Cassiopeia first and then look across from there!

Screenshot courtesy of Stellarium
Copyright Adrian Dening and Radio Ninesprings 2021