The Moon and Aldebaran
This week the moon wanes in illuminated phase and rises later because it is in the third week of its monthly cycle. It’s a good time to get out and take a look at the waning gibbous moon and some bright stars surrounding it.
On Thursday the moon will rise at about 10:30 pm among the brighter stars of Taurus (the Bull). The moon will first approach and then enter the big triangular-shaped set of stars that compose the face of Taurus. Taurus’ face is actually a family of stars formed from the same molecular hydrogen cloud. Astronomers call these stars the Hyades open star cluster. Unlike most star clusters, the Hyades’ stars are widely separated in the sky (about three finger widths across) because they are located only about 150 light-years from the sun.
Thursday night into Friday morning, September 19 to 20, the moon’s orbital motion will be carrying it past Aldebaran, the very bright, orange-tinted star that marks the bull’s southern eye. Aldebaran will be sitting to the lower left of the waning gibbous Moon. It is the brightest star in Taurus, the fourteenth-brightest star in the night sky and one of the easiest stars to find. Aldebaran is not part of the Hyades. It’s a different colour, and is much closer (66 light-years) than those stars. Observers who live in the Pacific Ocean region and Asia can watch the moon tackle Taurus in a dark sky.
During the rest of Thursday night, look for the tight little Pleiades Star Cluster sitting less than a fist’s width above the moon. Some people mistake this object for the Little Dipper. It is little, and it is somewhat dipper-shaped, but the genuine article is half the sky away – off to the Pleiades’ upper left.
On Thursday evening, the moon will reach its last quarter phase. At its last quarter phase, the moon rises around midnight and remains visible in the southern sky all morning. The moon will end the week as a thick, waning crescent tickling the toes of Gemini (the Twins) in the predawn sky.
Find everything you need to know about astronomical events in Star Walk 2.