Colorado Skies: Seven Sisters a starry watering can

At or near the top of the list of most interesting celestial sights in the early evening November Colorado sky is a small, closely-packed group of stars popularly known as the Seven Sisters or the Pleiades.

Located to the east of the overhead point and to the west of the bright ruddy Taurus star Aldebaran, this compact cluster of moderately bright naked eye stars is often erroneously referred to as the “Little Dipper.” The real Little Dipper is actually located due north, with the end of its “handle” anchored by the fairly bright “North Star” Polaris. Meanwhile, the Pleiades are perhaps better described as a sort of small, starry watering can rather than a dipper.

As one might expect, the Pleiades have generated a myriad of myths, legends, and folklore throughout history and around the globe, including those of the Aztecs, Chinese, Egyptians, Africans and Australian aboriginal tribes, as well as those of our own Native Americans. The name of the Pleiades comes to us courtesy of Greek mythology, in which these stars were once the seven daughters of Atlas and Pleione who were ultimately placed in the heavens to escape the unwanted attention of the mighty hunter Orion who is lurking in the night sky just to the southeast.

Interestingly, all of the Pleiades legends of antiquity refer to seven starry objects, but at present only six are easily visible to the unaided eye, thus prompting much speculation among astronomers over the mystery of the so-called “Lost Pleiad”. It is generally believed that one of the presently fainter stars of the Pleiades was at one time much brighter and more prominent than we now observe it. The question of which star is the actual lost Pleiad has generated considerable discussion and a certain amount of controversy among astronomers for decades.

Although only six of the Pleiades are prominently visible under normal circumstances, a sharp-eyed observer located at a dark sky observing site can, with the naked eye detect as many as a dozen or more stars in this fascinating star group. A pair of binoculars reveals nearly 50 stars, and a small, wide-field telescope brings more than a hundred stars into view. Long-exposure images obtained in large telescopes indicate that more than 500 stars exist in the Pleiades region of the sky.

Astronomers have long recognized that the Pleiades are one of a class of astronomical objects which are called open or galactic star clusters. Of the nearly 900 such star clusters known to astronomers, the Pleiades are especially interesting owing to their relatively close 400 light year proximity to the sun, and also to the fact that the entire cluster is enveloped in a gigantic cloud of gas and dust which is faintly illuminated by the light from the cluster’s stars. Unfortunately, this beautiful nebulosity is visible only on long-exposure images obtained through large aperture telescopes and is thus out of reach for even the above-average amateur astronomer. Even without their faint filmy veil, however, the Pleiades nonetheless still stand as one of the more beautiful starry hallmarks of the upcoming holiday season.

Elsewhere in the sky: The planet Venus shines brilliantly above the southwestern horizon for about two hours or so after sunset.