Northern Arizona astronomy: The Pleiades - a spectacular binocular object in the night sky

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Sky Chart

WILLIAMS, Ariz. - The Pleiades is an interesting and beautiful grouping of stars in the constellation Taurus, the bull, and is easily observed in the evening sky from fall through spring. The asterism, which is about two to three times the diameter of the full moon, is one of the most prominent celestial objects visible in the night sky to the naked eye or with binoculars.

At a distance of about 440 light years (135 parsecs) from us, it is one of the nearest star clusters to Earth. To astronomers, the Pleiades is known as M45, an open cluster of stars, loosely bound by gravity, and all moving through space together. Although there are well more than 1,000 stars in the grouping, only as many as 14 are discernable with the naked eye under the best of conditions, though the mythology of most cultures refers only to the brightest six or seven. The cluster, which is dominated by young hot blue stars, is estimated to be about 115 million years old.

Being situated relatively close to the celestial equator, as well as along the ecliptic, the Pleiades can be viewed from every continent except Antarctica and is the most observed and documented asterism by groups of people world-wide, even more so than the constellation Orion.

Although we see the Pleiades very prominently here in the Northern Hemisphere, the asterism has been known and documented in the mythologies of cultures all around the world since antiquity. Besides the European based Greeks, Celts, and Romans, the Aboriginal peoples of Australia, the Maori in New Zealand, the Persians and Arabs of the Near East, the Chinese, Japanese and Indians in Asia, the Swahili in South Africa, the Maya and the Aztec in Central America, and the Hopi, Navajo, Sioux, Cherokee and Inuit in North America, just to name a few, all have stories about the asterism we call the Pleiades.

This cluster has been observed by many societies for thousands of years. There is a one foot diameter bronze disk, which was located near Nebra, Germany, that depicts the Pleiades, among other celestial objects, which has been dated to 1650 BCE. Above prehistoric paintings of a bull in a cave in Lascaux, France, are six dots that are oriented with respect to the bull's eye in perfect alignment where the eye represents the bright star Aldebaran, and the six dots are the Pleiades. These cave paintings were made about 15-16,000 years ago.

Interestingly, different societies from around the world sometimes tell Pleiades stories that share similarities. The name, Pleiades, comes from Greek mythology. They were the seven sisters, the daughters of Atlas. Indian mythology describes the Pleiades as the six wives of six great sages. Both the Cherokee and Onondaga tribal stories are about a group of seven boys, while among the Pawnee the Pleiades are seen as seven brothers. Of course, other cultures have differing names that go along with their own mythological stories.

For many societies around the world, the appearance of the Pleiades often marks important or significant seasonal changes or agricultural events. For many tribes in Africa, the Pleiades mark the beginning of the planting season. In the Swahili language, the Pleiades are called "kilimia" meaning to "cultivate."

The Zuni, in the American Southwest, also used the Pleiades in their agricultural calendar. To them, the Pleiades were known as the "Seed Stars." When the Pleiades disappeared on the western horizon during spring, it was time for planting seeds as the danger of frost had passed. The Zuni also knew to finish all of their planting and harvesting before the Pleiades returned on the eastern horizon and with them the return of colder autumn weather and frost. In many groups the Pleiades appearance in the heavens is seen as the arrival of the rainy season.

In Japan the Pleiades is a cluster of six stars which are known as Subaru, meaning "united." This cluster can be seen as the logo found on Subaru cars and is also the name of the large Japanese telescope on Mona Kea, Hawaii.

So, when you go outside in the evening, look to the right of Orion, past the bright star Aldebaran, and you will find a grouping of several relatively bright stars. Visually, M45 is one of the most beautiful open clusters in the night sky. Through a telescope or binoculars, under ideal observing conditions, a hint of bluish nebulosity may be observed around the cluster. This is light reflected from the dust and gas that surrounds the hot young blue stars and though much more prominent in astronomical photographs taken with cameras which are capable of collecting the light over time, unlike our eyes, through binoculars the Pleiades is still a spectacular cluster of 50 plus magnificent stars that fill the center of the field of view. And, as you observe, remember that it has also been an historical agricultural and mythological marker for ancient societies over the millennia that has helped people to survive.

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