7 - Algol, the demon of autumn

Summary

While the Dipper may rule the sky of spring and early summer, different stars and new opportunities await the sky's watchers in late summer and fall.

High in the western sky is the “Summer Triangle” of Vega, Deneb, and Altair, leading their respective constellations of Lyra the Harp, Cygnus the Swan, and Aquila the Eagle. School children watch for the triangle to rise in the east during late northern hemisphere spring, for the letter “V” shape of its three bright stars promises them that summer vacation is about to begin. The position of the “V” high in the west as autumn begins is a sign that vacation is over. To the east of the Triangle flies the square of Pegasus, the winged horse. I have never thought this asterism looks much like a horse, let alone the kind that flies, but its four bright stars do resemble a baseball diamond. You can easily spot home plate and the bases, while the Milky Way to the north shines with the excitement of the fans.

A little further to the east is Andromeda the Princess, and Perseus. We now focus on Beta Persei. But why Beta? In 1603 Johann Bayer published a star atlas in which stars in the different constellations were given Greek letters in approximate order of brightness. Many stars are numbered instead, according to John Flamsteed's 1725 catalog, which used increasing numbers from west to east in each constellation.