Papworth Astronomy Club

The club was treated to a tour de force of a talk from Gary Poyner, who came over from Birmingham to tell us about of variable stars in all their different forms. Gary has been observing these objects for forty years and is an acknowledged expert in the field, having been head of the variable star section of the BAA. He started the talk with a striking image of the summer constellations overlaid with an enormous numbers of variable stars that are visible by eye or through binoculars. This came as a surprise to those of us who thought that there were only a few such objects, like the famous Algol and Mira. Gary then went into detail about the different astrophysical mechanisms that give rise to variability in the brightness of stars; these included simple dimming of light by eclipsing binary stars to dramatic shifts of stellar material to form accretion discs. Throughout the talk he used animations to illustrate each mechanism and this certainly helped the non-expert. From the perspective of the amateur observer, it is interesting to see how accurate light curves of the many different types of variable stars can be produced just by using binoculars, a small telescope, or even the naked eye. The key is to use star charts with reference stars of defined magnitudes. Apparently it is possible to achieve an accuracy of 1/10 magnitude by eye and of course much greater with CCD images. Gary’s talk certainly gave us food for thought about the contributions that amateurs can make to astronomy through work on objects like variable stars. The following websites give more details:

• http://www.britastro.org/vss
• http://www.aavso.org