Late summer VARIABLES
A casual look at the night sky gives the impression that the stars are constant and unchanging. While it’s true that many stars remain fairly constant over the course of a human lifetime, there’s a large number of stars that change quite rapidly, sometimes in a matter of hours.
The ancient Egyptians knew that the star Algol (Beta (β) Persei) in Perseus changed in brightness, but it wasn’t until 1638 when Johannes Holwarda discovered that the apparent magnitude of the red giant star Mira (Omicron (o) Ceti) in the constellation of Cetus, the Whale varied over a period of about 11 months. Eventually, other stars with similar behaviour were discovered and, before long, a new area of astronomy arrived: the study of variable stars.
Today, variable stars play an important role in stellar astrophysics – they provide
