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Facts About the Big Dipper

You don't have to be an astronomer to pick the Big Dipper out of the night sky in the northern hemisphere. The Big Dipper is an "asterism," a band of seven stars that together forms a familiar pattern. The Big Dipper is not a constellation unto itself, but is a portion of Ursa Major, the Great Bear. The Big Dipper is as useful a tool to locate other stars and constellations in the sky, acting almost as a sign that can point to various stellar features.

Identification
- The seven stars that compose the Big Dipper, which looks like a giant ladle in the sky, are all bright enough to stand out, making the Dipper recognizable even at a glance. Three stars form the handle and ̶0;attach̶1; to the four that form the rectangular bowl of the Dipper. The asterism is part of a much larger constellation that represents a bear, with the handle of the Dipper in the spot where the bear̵7;s tail is (even though it makes for a much longer tail than any earthly bruin possesses).
Pointers
- The two stars at the end of the bowl furthest away from the handle are Dubhe and Merak, also known as "the Pointers." By following a straight line from the bottom star in the bowl of the two, Merak, through Dubhe, you will come to a somewhat bright star called Polaris, the Pole Star. Polaris is almost exactly on that part of the heavens where a line straight up from the North Pole of the Earth would intersect. For this reason, Polaris appears to remain stationary as the Earth rotates--a movement that makes the stars all appear to move in the sky. Due to the Earth̵7;s rotation, the Big Dipper appears to circle Polaris, making one complete revolution around the star per day.
Size
- Dubhe is a giant yellow star that lies 105 light-years from Earth, meaning that its light needs 105 years to reach your eyes, traveling at the rate of about 186,000 miles per second. Dubhe is 105 times brighter than our own Sun, according to the Starry Skies website. Its Pointer companion, Merak, is 33 times brighter than the Sun, lying at a distance of 60 light-years away.
Significance
- Stargazers may utilize the Big Dipper to find other prominent stars and constellations. By following an imaginary arc from the handle and out on a path through the night sky, you will find it intersects Arcturus, a very bright star in the Bootes constellation. Continuing along this arc you will encounter Spica, a luminous star in Virgo the Virgin. Using the other two stars in the bowl of the Dipper and drawing a line from the top one through the bottom brings you to Regulus, a bright star in Leo the Lion. The imaginary line that you draw through the two top stars in the bowl out away from the handle leads you to Capella in Auriga the Chariot Driver.
Horse and Rider
- The handle of the Big Dipper contains three stars, with the middle one of particular interest. The middle star is Mizar, part of a multiple star system in which stars orbit each other. Mizar has a partner star named Alcor that you can separate from Mizar with the naked eye if you have good eyesight. According to Astropix.com, Mizar and Alcor are nicknamed the Horse and Rider.

Astronomy