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Starwatch: getting to know the Great Bear

Starwatch: getting to know the Great Bear

The seven brightest stars in Ursa Major, the Great Bear, form the shape known as the Plough, or the Big Dipper, or by a number of other names in different cultures.

The association with a bear dates to antiquity, when it was listed in Ptolemy’s original 48 constellations from the second century AD. Now incorporated into the International Astronomical Union’s list of 88 modern constellations, it covers a little more than 3% of the entire night sky, making it the third largest constellation by area.

The star Mizar, in the handle of the Plough, or the tail of the bear, is actually a double star and on still nights, from locations without light pollution, its fainter companion, called Alcor, is visible to the naked eye.

The constellation can also be used to pinpoint Polaris, the pole star. Starting at Merek and extending a line through Dubhe leads up to the pole star.

Because Ursa Major is so high in the northern sky it is difficult to see from much of the southern hemisphere. From Cape Town, South Africa, for example, only its legs are visible, sticking up from the northern horizon at this time of year.

Source: theguardian.com