Ursa Minor
|
|
Ursa Minor is a constellation in the northern sky, the name of which means Small Bear in Latin. It is one of the 88 modern constellations, and was also one of the 48 listed by Ptolemy. It is notable as the location of the north celestial pole, although this will change after some centuries due to the effects of precession.
Notable features
Ursa Minor contains an asterism colloquially known as the "Little Dipper" because its seven brightest stars seem to form a ladle, or dipper shape. The star at the end of the dipper handle is Polaris, the "North" or "Pole Star".
Polaris can also be found by following a line through the two stars which form the end of the "bowl" of the Big Dipper, a nearby asterism found in the constellation Ursa Major.
The seven stars are the origin of the Latin word septentrion meaning "north," and now found as the adjective septentrional (northern) in French and Spanish, to go with adjectives for the other three directions that refer to the position of the sun.
The two brightest stars are:
- Polaris (α UMi): a yellow supergiant of spectral type F7 and an apparent brightness of 2.02m
- Kochab (β UMi): a giant orange star; spectral type K4; brightness 2.08
History
This constellation is said to have been introduced in the 6th century B.C. by the Greek astronomer Thales of Miletus, but was certainly already used as a guide by sailors.
In ancient time, Ursa Minor was named the Dragon's wing, and was considered a part of Draco. The dragon's wing as an asterism is now long forgotten.
Mythology
The constellation of Ursa Minor, which, when including less visible stars which are still visible to the naked eye, vaguely resembles a bear (with an unusually long tail). In consequence, together with the nearby Ursa Major, it formed the basis of the myth of Callisto. The tail was said to have been lengthened, from that usually expected for a bear, due to the incessant spinning of the bear, by the tail, around the pole.
In earlier times, Ursa Minor was considered just to be seven close stars, and mythologically was regarded, as such, as sisters. In early greek mythology, the seven stars in Ursa Minor were considered to be the Hesperides, daughters of Atlas. Together with other constellations in the zodiac sign of libra (i.e. Bo�tes, Ursa Major, and Draco) it may have formed the origin of the myth of the apples of the Hesperides, which forms part of The Twelve Labours of Herakles.
To many other cultures Ursa Minor was the Hole in which the earth's axle found its bearing. In Hindu mythology, the Pole Star is Dhruva (the word means pole today) and there is a story behind him becoming a star.