Adrian Dening's Stars Over Somerset

Wednesday, 3 May 2023 17:00

Monday 8th to Sunday 14th May 2023

The brightness or magnitude of most stars is pretty constant. They only twinkle because the light being radiated from them is distorted by our atmosphere, but their overall magnitude remains the same night to night. Some stars are classed as "variable stars" and these can vary considerably in magnitude - some stars swell and shrink in size and others may have their light partially blocked from reaching us as an exoplanet orbits around them.

This week try having a look at one such variable star, R Coronae Borealis which is located towards the centre of the "U-shaped" constellation Corona Borealis. Changes in its chemical composition mean the star can vary between a magnitude of +5.7 at maximum when it is just visible with the naked eye, down to a minimum of +15 which is serious telescope territory!

If you go outside around midnight on 10th or 11th, the Moon will have not yet risen above the horizon and Corona Borealis will be found high up towards the south east to the right of the constellations Cygnus "the Swan", Lyra with its bright star Vega and Hercules. Will you be able to see it?

Closer to home and definitely not needing a telescope, there are some excellent opportunities to observe the International Space Station next week, but you will have to stay up late. The dates for your diary are Thursday 11th at 2.40am, Friday 12th at 1.52am and Saturday 13th at 1.01am. In each case, the ISS will appear over the horizon to the west and spend 6 - 7 minutes passing almost directly overhead before disappearing to the east.

Screenshots courtesy of Stellarium
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