The Pleiades are everyone’s favorite star cluster. Or they would be, if everyone knew where to find them. Look for a closely-spaced group of six brilliant stars in the sky above and just to the right of the moon this evening at nightfall. Their combined radiance intermingles to produce that characteristically diffuse blue light, making them easily identifiable in the winter sky.
Aldebaran is that bright ruddy star visible just above and to the left the moon in the early evening. Those living in the far north latitudes will be able to see Aldebaran vanish behind the moon for about an hour. The occultation – the scientific word for this cosmic hide-and-seek – will be visible in Greenland, Iceland and northern Europe. Aldebaran will vanish behind the dark side of the moon and reappear on the bright side.
The occultation of Aldebaran by the moon is the second of a series that will continue until 2018. The visibility of the occultation will move steadily southward until it can be seen in the Southern Hemisphere just south of the Equator. It will then move northward again. Aldebaran is the the brightest star in the constellation Taurus the Bull, and may be thought of as the red bull’s eye.
The Pleiades (Messier 45 or M45) or the Seven Sisters are an open star cluster, and also part of Taurus. As one of the closest star clusters to earth, they are highly visible and storied in the myths of many cultures worldwide. The name is derived from the Greek word for sailing, since the helical rising of the cluster in May marked the beginning of the navigation season in the Mediterranean.
Unlike many other constellations and sky formations, the Pleiades are actually a related group of stars, rather than a chance alignment visible from earth. The diffuse light or nebulosity between the stars is the result of dust reflecting the light the young, blue stars. While most observers can see only six of the stars with the naked eye, the cluster actually contains hundreds.