For the week including February 25, 2011

THE BIG DIPPER

Around eight o’clock, the most famous and easily recognized group of stars, the Big Dipper, can be found standing on its handle in the northeast. This group of stars seems to be just about everyone’s favorite and can be found anywhere from Vincent Van Gogh’s Starry Night over the Rhone to the Alaska state flag. As our diagram shows, the stars of the Big Dipper are actually part of the larger constellation of Ursa Major, the Great Bear. The romantic sounding names of the Big Dipper’s stars come down to us from ancient Arabic and most of them reflect their connection to the Great Bear. Over the years, European astronomers shortened the names and altered many of their unfamiliar pronunciations.

Dubhe: The name Dubhe originated in the Arabic phrase Thahr al Dubb al Akbar meaning “The Back of the Greater Bear”.

Merak: This name comes from the Arabic designation Al Marakk indicating “The Loin of the Bear”.

Phecda: This star’s name had many different spelling variations over the centuries. It’s believed that the primary source for the name came from the Arabic term Al Falidh meaning “The Bear’s Thigh”.

Megrez: Originally this was Al Maghrez meaning “The Root of the Bear’s Tail”.

The last three stars, Alioth, Mizar and Alkaid, form the handle of the Big Dipper, but also represent a peculiarity of the Great Bear. The detail on the right in our illustration was drawn by Stanley Hall and appeared in 1825 as part of a set of constellation cards called Urania’s Mirror. In his sketch, Hall reproduces features of the Great Bear that had been depicted in star atlases for many hundreds of years. Besides having a strange pointy-looking face, Ursa Major has a tail that’s much longer than the ones that are standard equipment on bears we see nowadays. Some historians attribute the discrepancies in rendering to the probability that the astronomers who produced drawings for the atlases were unlikely to have ever encountered most of the exotic animals they depicted among the stars. Other historians hold that the astronomers were just lousy artists. Both are correct. Anyway, long-tailed bears were pretty unfamiliar to Arabic astronomers who chose some unlikely themes for these stars.

Alioth: The derivation of this name is unclear to researchers. It may originate with the Arabic word Alyat from a phrase meaning “The Fat Tail of the Eastern Sheep”. But it’s anyone’s guess as to how a sheep wandered in here.

Mizar: This name comes from the Arabic Mi’zar meaning a girdle. Perhaps the Great Bear was concerned about all that talk about a “fat tail”. When you look at Mizar, you may be able to see the faint star Alcor sitting close by. This star, unremarkable but for its proximity to a conspicuous neighbor, has received more than its share of attention. Popular legends have it being used for thousands of years as a test of visual acuity. It seems that everyone from the Roman Legions down to the US Navy has used this star for an eye test.

Alkaid: This name is a shortened form of the Arabic phrase Al Ka’id Banat al Na’ash, which means “The Head Mourner”. This name probably referred to all three tail stars and came from an earlier star legend that has passed from history.

Sadly, our Big Dipper won’t last forever. With the exception of Dubhe and Alkaid, the rest of the stars of the Big Dipper are part of a cluster of related stars that move through space in the same direction. In a few hundred thousand years, when the stars have moved far enough apart, people may wonder how anyone ever saw a dipper-shape here at all.

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