Adrian Dening's Stars Over Somerset

Wednesday, 15 May 2024 17:00

Monday 20th to Sunday 26th May 2024

I'm going to concentrate on the early hours of Friday 24th when we have a full Moon. By 1am, the Moon will be heading towards the south and if you are outside at that time, the bright star Antares will be located a little to the left of the Moon.

Antares is a red supergiant and it is actually classed as a "variable star". This means that its magnitude or brightness can change between +0.6 at its brightest, down to around +1.6 and I believe that currently it is around +1.0 so very easy to spot. Antares is part of a binary star system, but you will only be able to resolve the main red supergiant star - its smaller companion will remain invisible. Antares is huge - up to 16 times the mass of our Sun and if it was placed at the centre of our Solar System, the star would extend all the way out to Jupiter!

Binary stars orbit around each other because of their mutual gravity and if you can see both stars in your telescope, they are known as "visual binaries".

Getting back to 1am on 24th, immediately to the left of the Moon you can find the Spider Globular Cluster of stars, also known as M4 in the Charles Messier catalogue. It will be a real challenge to see with your telescope because of the proximity of the full Moon which is the ultimate source of light pollution.

Globular clusters are collections of up to millions of stars, kept together by their mutual gravity and the centre of the cluster is brighter where they are concentrated. Last week I suggested looking at M44 which is an open cluster - a small group of recently-born stars who gradually drift apart from each other.

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Screenshots courtesy of Stellarium
Copyright Adrian Dening and Radio Ninesprings 2024