Astronomy for Everyone

The Pleiades, with nebulosity from the cloud of gas from which they formed.

If you look out to the east when the sky is dark during the fall months, you will see one of the most famous and beautiful star groupings in the sky. It looks like a small faint question mark, made up of stars. This star grouping, or cluster, is the Pleiades (pronounced PLEE-uh-deez), or Seven Sisters. The Pleiades are located within the constellation Taurus, the Bull, and represent the bull’s shoulder.

In Greek mythology, Taurus represented the king of the gods, Zeus, who disguised himself as a white bull with golden horns to attract the beautiful maiden, Europa. When Europa seated herself on the bull’s back, he swam away with her to Crete, which is why we see only the animal’s head and forequarters in the constellation.

Below the Pleiades you can see a large sideways "V" with a large red star at one point. This star represents one of the bull’s eyes, and is named Aldebaran (pronounced al-DEB-air-un), Arabic for "the follower". It is so named because the star "follows" the Pleiades in the sky. Located with Aldebaran is another open star cluster, named the Hyades (pronounced HI-uh-deez). There are several hundred stars in this cluster, with nearly 150 easily visible in binoculars. These stars come in several different colors, making the Hyades a popular binocular object. Because it is relatively close to Earth, at a distance of about 150 light-years, it is well studied by professional astronomers as well.

By contrast, the Pleiades represents a relatively young open cluster of stars, shrouded in gas and dust. Best viewed through binoculars, the stars in this cluster are a bright blue-white. According to Greek Mythology, the Pleiades were seven sisters who were being pursued by the hunter, Orion. They begged the gods for help, and Zeus, hearing their plea, first turned them into pigeons and then into stars in the sky. The Greeks, like most modern observers, saw only six stars, however, and had to come up with some explanation concerning the "invisibility" of the seventh sister. The myth then went on to explain that one of the sisters hid her light in shame, because she had married a mortal.

There are two other open star clusters within Taurus that are great binocular targets. One of them is NGC 1647. It is located just northeast of Aldebaran and contains about 30 stars. The other is NGC 1746, which is located on a line from Aldebaran to the star that marks the tip of the northern horn of the bull. It contains about 60 stars.

An open star cluster, also called a galactic cluster, is a grouping of stars that usually were formed from the same cloud of dust and gas. The stars are arranged in random patterns and sometimes exhibit different colors. Many open star clusters are quite large, and are best viewed through binoculars, as opposed to a telescope. Sometimes you can even see faint wispy remnants of the cloud that formed the stars.

For more information about star clusters, take a trip to your local public library and pick up a book on astronomy. And remember - when it’s dark, go outside and look up! You never know what you’ll find.