Most of the star pictures that hang in the night sky are nothing more than coincidence. The stars that make up the pictures are unrelated, and can be hundreds or even thousands of light-years apart. They make “pictures” only because they line up in roughly the same direction from Earth.
But a few of these pictures are more than just chance - their stars really are related to each other.
Two examples flank the crescent Moon this evening. The Hyades cluster is close to the left of the Moon. Its brightest stars form a letter “V” that outlines the face of Taurus, the bull. And the Pleiades cluster is a little farther to the right of the Moon. Its brightest stars form a tiny dipper.
Each cluster contains several hundred stars, all of which formed together, from a single giant cloud of gas and dust. The Hyades is older, so it doesn’t have as many hot, blue stars as the Pleiades. And the Hyades is less than 150 light-years from Earth, while the Pleiades is about three times farther.
Because the stars of each group are the same age, and formed from the same raw ingredients, they’re good laboratories for studying how stars evolve.
Look for the Hyades and Pleiades flanking the Moon this evening. The brightest star in the bull’s face, orange Aldebaran, isn’t a member of the Hyades - it’s just one of those chance alignments. And another bright light stands above them - the planet Jupiter. More about Jupiter and the Moon tomorrow.
Script by Damond Benningfield, Copyright 2013
For more skywatching tips, astronomy news, and much more, read StarDate magazine.