When can we see further – during the day, or the night? Obviously during the night, because we can see the stars, which are vastly more distant than anything on Earth. But what is the furthest object that we can see with the unaided eye?
The answer is the Andromeda Galaxy. With the return of the darker evenings of autumn, the constellations of Perseus and Andromeda are reappearing high in the south-eastern sky. Wait for a clear moonless night, and find a dark sky location, as far as possible from the polluting effects of night lighting. Then use the diagram shown here to locate the four stars making up the great square of Pegasus. Follow the line of stars to the top left of the square. And in the position shown on the diagram, you should see a faint fuzzy patch.
This faint fuzzy patch is a separate galaxy of about 100,000,000,000 stars. Large telescopes can see numerous individual stars in the galaxy. It was Edwin Hubble, about 90 years ago, who first measured the distance to Andromeda, and demonstrated that it lay far beyond the outermost boundaries of our own Milky Way Galaxy. The light reaching your eyes now actually set off from Andromeda about 2.5 million years ago, when our very distant ape-like ancestors were roaming the plains of Africa.
After our usual summer break, the Torbay Astronomical Society will be starting its meetings again in September. On Thursday, September 13, we shall be hearing from Dr Dave Acreman, from Exeter University, on the topic The Spiral Arms of our Galaxy. Then on Thursday, September 20, our observational evening will be focussing on the double star Albireo and the planetary Nebula M57.
All meetings are held at Torquay Boys’ Grammar School, Shiphay Manor Drive, from 7.30pm. The lecture meetings are in their Business & Enterprise Suite, and observational evenings start out in the Physics Lab PL4. Visitors and new members are very welcome. Membership for the year is £15, and visitors are charged £3 for lectures and £2 for observational evenings.