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Ursa Major

(UR-sah MAY-jer)

The Great Bear

Perhaps the most familiar star figure is the Big Dipper, seven moderately bright stars in the northern sky. The Big Dipper is an asterism, only part of the greater constellation of Ursa Major, the Big Bear. (The constellations are the "official" star patterns, many of which have come down to us from the ancient Greeks and Romans. The "unofficial" ones are called "asterisms" and are often a sub-grouping of stars within a regular constellation.)

Visibility: At least part of Ursa Major is visible all year long in the northern sky. The Great Bear endlessly circles the North Star (also known as Polaris or Alpha Ursae Minoris). At 8:00 p.m. in February, it completely rises above the north-northeast horizon. At 9 PM (Standard Time) in April and May the constellation is at its highest in the northern sky. At 9:00 p.m. (Standard Time) in September the stars representing the bear's feet dip below the north-northwest horizon.

What to look for: The stars of the Big Dipper all have names: Duhbe (Alpha Ursae Majoris), Merak (Beta Ursae Majoris), Phecda (Gamma Ursae Majoris), Megrez (Delta Ursae Majoris), Alioth (Epsilon Ursae Majoris), Mizar/Alcor (Zeta Ursae Majoris) and Alkaid (Eta Ursae Majoris). A constellation's stars are usually given Greek letters (starting with the beginning of the Greek alphabet) to denote the stars from the brightest to dimmest. The Dipper is an exception. The stars of Ursa Major are lettered from right to left.

To see the Bear, begin with her long tail (also known as the handle of the Big Dipper). The bowl of the dipper is the Bear's hindquarters. The remainder of the Bear is drawn with fainter stars.

The Bear's back extends from the bowl of the dipper out to faint Omicron Ursae Majoris (the tip of the nose). Three of the Bear's paws are visible, each made up of a couplet of stars. One of the Bear's front paws is marked by the stars Iota Ursae Majoris and Kappa Ursae Majoris. One rear paw is marked by Lambda Ursae Majoris and Mu Ursae Majoris, and the other is marked by Nu Ursae Majoris and Xi Ursae Majoris. These stars that form the paws of the Bear also form an asterism known to the Arabs as the Three Leaps of the Gazelle.

Look closely at Mizar, second star from the end of the Bear's tail. It has a faint companion star, Alcor (80 Ursae Majoris.). A small telescope reveals that Mizar is itself a double. Mizar and Alcor mean Horse and Rider in Arabic.

Mythology: Zeus (the Romans' Jupiter), King of the Olympian Gods, fell in love with a mortal woman, Callisto. Soon after, Callisto gave birth to a son, whom she named Arcas. Zeus' enraged wife Hera (Juno, in Latin), Queen of the Gods, turned Callisto into a bear, condemning her to wander the forest alone. 

Fifteen years later, Callisto encountered a young hunter whom she recognized as her son, Arcas. She rushed to embrace him. Arcas, seeing the huge bear charging at him, drew his bow in defense and was about to release his arrow when Zeus spotted the developing tragedy. He grabbed the bear by her tail, whirled her around his head (thus stretching out her tail until it was very long) and slung her up into the sky. Taking pity on Arcas, Zeus transformed the young hunter into a bear cub, Ursa Minor, and slung him by his tail into the northern sky to join his mother, Ursa Major, where they both continue to guide travelers to this day.

Many cultures have recognized the seven brightest stars of Ursa Major, but have seen other images. In Europe, they form Charles' Wain, the horse-drawn Wagon of Charlemagne. In England and Ireland, they are seen as the Plow. In much of Africa, this pattern is seen as the Drinking Gourd, an image that in America has become our Big Dipper. African slaves in America used a song mentioning the Drinking Gourd's northern appearance to pass information to others of the route to freedom.

The image of a Bear is widespread over much of the Northern Hemisphere. From Europe through Siberia and across the Bering Strait to the American northwest, many people saw a bear (the four stars of the Dipper's bowl), followed by three hunters (the three stars of the Dipper's handle.) This widespread image of a bear occurring across the globe hints at the possible great age of the constellation. Another clue to the age of Ursa Major has to do with its size. It is the third largest of the classical constellations. Early constellations tended to be bigger than those conceived later in history. 

A Deeper Look: You can use the Dipper and the Bear to find other constellations. Trace a line through the two pointer stars at the north end of the Dipper's bowl and you will come to another moderately bright star, Polaris (Alpha Ursae Minoris), popularly called the North Star. It is around a point very close to Polaris that the stars rotate overhead in the evening sky throughout the night, and Polaris is commonly used as a navigational star.

Poke a hole in the bowl of the Dipper and water drips south onto the back of Leo, the Lion.

Finally, follow the arc of the Dipper's handle to the southeast and find the bright star Arcturus (Alpha Boötes) in Boötes, the Herdsman.