Adrian Dening's Stars Over Somerset

Saturday, 8 March 2025 16:50

Monday 10th to Sunday 16th March 2025

Venus is a very popular target in the early evening sky at the moment. Look towards the west any evening next week to see it, but on Tuesday 11th in particular, a telescope will reveal the planet in a beautiful 5%-lit crescent phase. If you are looking west at 7pm, there is also the chance to spot Mercury just below and to the left of Venus.

Venus is currently shining very brightly at a magnitude of around -4.0 and this is a good opportunity to explain the magnitude scale in a bit more depth. Imagine a reference star has a brightness magnitude of zero to start with. The scale works backwards, so anything brighter than the reference star will have a negative number and the fainter an object is, the more positive its number will be.

The brightest star in the night sky is Sirius with a magnitude of -1.44 and around 7pm next week, Sirius can be found to the south. Above and to the left of Sirius is another bright star, Procyon, that has a magnitude of +0.4 or in other words, not quite as bright as Sirius. Above and to the right of Sirius you will find the constellation of Orion, with its red giant alpha star Betelgeuse shining at +0.45 (similar to Procyon) and the young beta star Rigel at +0.12 which is a bit brighter.

To put all this into context, our own Sun has a magnitude of -26.74 which is why you never try to look at it through binoculars or a telescope! With the naked eye, from a dark location, you can see objects down to a magnitude of about +6.0 so things like the Great Orion Nebula in the sword of Orion at +2.9 can just be identified. Anything with a magnitude more positive than +6.0 requires binoculars or a telescope.

www.starsoversomerset.com

Screenshots courtesy of Stellarium