Ursa Minor

From Wikipedia, the free encyclopedia

Ursa minor
click for larger image
Abbreviation	UMi
Genitive	Ursae Minoris
Symbology	The Little Bear
Right ascension	15 h
Declination	75°
Area	256 sq. deg. Ranked 56th
Number of main stars	{{{numbermainstars}}}
Number of stars (Bayer-Flamsteed)	23
Number of stars with planets (BF, variable, other stars)	{{{numberstarsplanets}}}
Number of bright stars (magnitude < 3)	2
Number of nearby stars (Distance < 100 ly)	2
Brightest star	Polaris (App. magnitude 2.02)
Nearest Star	π¹ UMi (Distance: 70.8 ly)
Meteor showers	Ursids
Bordering constellations	Draco Camelopardalis Cepheus
Visible at latitudes between +90° and −10° Best visible at 21:00 (9 p.m.) during the month of June

Ursa Minor (IPA: /ˈəːsə ˈmʌɪnə/) 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 precession of the equinoxes.

1 Notable features
2 Notable deep sky objects
3 History
4 Mythology
5 Notable and named stars
6 See also
7 External links

[edit] Notable features

Ursa Minor is 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 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 two brightest stars are:

Polaris (α UMi): a yellow supergiant of spectral type F7 and an apparent brightness of 2.02m
β UMi (Kochab): a giant orange star; spectral type K4; brightness 2.08

[edit] Notable deep sky objects

Ursa Minor Dwarf, a dwarf galaxy.

[edit] History

This constellation is said to have been introduced in the 6th century BC 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. Aratus called the constellation Κυνόσουρα (Kunosoura) meaning "dog's tail". The name was later adapted to Latin as Cynosura.

[edit] Mythology

The constellation of Ursa Minor, 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.

The variant of the story, in which it is Boötes that represents Arcas, Ursa Minor was considered to represent a dog. This is the older tradition which sensibly explains both the length of the tail and the obsolete alternate name of Cynosura (the dog's tail) for Polaris. (It also clarifies the otherwise inexplicable etymology of "cynosure.")

In even earlier times, Ursa Minor was considered to be just 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. Boötes, 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 Heracles.

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.

[edit] Notable and named stars

BD	F	Names and other designations	Mag.	Ly away	Comments
α	1	Polaris, Alpha Ursae Minoris, Pole Star, Lodestar, Alruccabah, Cynosura, Phoenice, Tramontana, Angel Stern, Navigatoria, Star of Arcady, Yilduz, Mismar, Polyarnaya	1.97	431	< cynosūra < κυνόσουρα "The dog’s tail" Cepheid variable
β	7	Beta Ursae Minoris, Kochab, Kokab, Kochah	2.07	126	< الكوكب الشمالي az-kawkab aš-šamāliyy The north star (lit. heavenly body) [named when it was the pole star]
γ	13	Gamma Ursae Minoris, Pherkad, Pherkad Major	3.00	480	< فرقد farqad calf < ? alifa al farkadayn The dimmer of the two calves [along with the brighter Kochab]. Delta Scuti type variable star
ε	22	Epsilon Ursae Minoris	4.21	347	RS Canum Venaticorum type variable star
	2	2 Ursae Minoris	4.24
	5	5 Ursae Minoris	4.25
ζ	16	Zeta Ursae Minoris, Alifa al Farkadain	4.29	376	< ? alifa al farkadayn The dimmer of the two calves [originally applied to Pherkad]
δ	23	Delta Ursae Minoris, Yildun, Gildun, Vildiur, Yilduz, Pherkard	4.36	183	< Turkish yıldız star
	4	4 Ursae Minoris	4.80
η	21	Eta Ursae Minoris, Anwar al Farkadain, Alasco	4.95	97.3	< ? anwar al-farkadayn The brighter of the two calves [originally applied to Kochab]
θ	15	Theta Ursae Minoris	5.00	830
	11	11 Ursae Minoris, Pherkad Minor	5.02
	19	19 Ursae Minoris	5.48
	18	18 Ursae Minoris	5.73
	24	24 Ursae Minoris	5.78
λ		Lambda Ursae Minoris	6.31	880
	20	20 Ursae Minoris	6.36
	3	3 Ursae Minoris	6.43
π¹		Pi-1 Ursae Minoris	6.58	70.8	double star; component magnitudes: 6.9, 7.8
	9	9 Ursae Minoris	6.64
	8	8 Ursae Minoris	6.83
π²		Pi-2 Ursae Minoris	6.89	384
	14	14 Ursae Minoris	7.52