The Big Dipper

The Big Dipper in Ursa Major

The Big Dipper
Jose Juan Gutierrez's image for:
"The Big Dipper in Ursa Major"
Caption: The Big Dipper
Image by: Rursus
© Creative Commons Attribution-Share Alike 3.0 Unported license.

The Big Dipper is one of the brightest and most recognizable asterisms in the sky. The Big Dipper is an asterism of seven stars in the northern skies, and can be easily found during all seasons except fall, when it lies low on the horizon. The group of stars in the Big Dipper forms part of the circumpolar stars, which remain near Polaris throughout the year, therefore, they´re visible most of the times. Because the Big Dipper is easily seen in the northern sky, it has been mentioned in the tales of ancient cultures. Explorers and travelers often use the Big dipper as a navigation aid.

The Big Dipper was used in ancient times as a navigation aid by sailors and other travelers. It was probably due to its brightness and to the fact that it is circumpolar to Polaris, the North Star. Depending on your location, circumpolar stars might be directly overhead for those living in the northern latitudes, and will remain visible throughout the entire year. The proximity of the Big Dipper to Polaris provides a major starting point from where to locate other stars in the sky. Indeed, Polaris is one of the major points from where to start our search for other stars, asterisms or constellations in the sky.

The Big Dipper, which is not a constellation by itself, forms part of the constellation of Ursa Major, and is composed of seven stars, with Dubhe,  Merak, Phecda and Megrez, forming the bowl, and Alioth, Mizar and Alkaid forming the handle. While five of the stars of this asterism remain fixed within its group, the two stars at both ends, Dubhe and Alkaid are moving towards each other, and in 50,000 years from now, they will constitute the bowl of the new Big Dipper, while Phecda and Merak will become the handle.

Locating the Big Dipper

One of the first stars that can be found in the sky using the Big Dipper as reference is Polaris, the North Star. Polaris is part of the Little Dipper, an asterism that resembles The Big Dipper, although overturned. Drawing an imaginary line from Alkaid and extending through Polaris, then continuing for about the same distance of this star pair distance, you´ll find to Polaris. Drawing an imaginary line from Alkaid and extending through Polaris, then continuing for about the same distance of this star pair leads to Polaris.

An imaginary line from Megrez to Phecda and about eight times that distance ahead leads to Regulus in the constellation of Leo. Another line from Megrez to Dubhe and continuing approximately seven times that distance leads to Capela in Auriga. Following the curve formed by Mizar and Alkaid leads to Arcturus in Bootes and continuing a bit further one finds Spica in Virgo. A diagonal line from Phecda to Dubhe and stretching it to about another similar expanse of space leads to a Messieur object known as M8, which is a spiral galaxy about 12 million light years away. Using this technique of drawing imaginary lines from star to star, it´s easy to navigate around the night sky.

The Big Dipper has been known since ancient times. In the Bible, the Big Dipper is mentioned as the seven stars in Amos 5:8. In Hindu astronomy, it was known as Sapta Rishi, which means the seven great sages. In Mongolia it is known as the seven gods. In the British Isles, it is known as the Plough, although in Ireland, it is most referred as the Starry Plough. In Native American mythology, the bowl was considered as a giant bear, and the handle was a group of warriors chasing the bear. According to, the Big dipper never disappears from sight at latitudes of 40 degrees or more in the northern skies, and this asterism is portrayed on the Alaskan state flag, as well.

More about this author: Jose Juan Gutierrez

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