Ursa Minor
Overview
 
Ursa Minor also known as the Little Bear, is a constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 in the northern sky. Like the Great Bear
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...

, the tail of the Little Bear may also be seen as the handle of a ladle, whence the name Little Dipper. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

, and remains one of the 88 modern constellations. Ursa Minor is notable as the location of the north celestial pole
Celestial pole
The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere...

, although this will change after some centuries due to the precession of the equinoxes
Precession of the equinoxes
In astronomy, axial precession is a gravity-induced, slow and continuous change in the orientation of an astronomical body's rotational axis. In particular, it refers to the gradual shift in the orientation of Earth's axis of rotation, which, like a wobbling top, traces out a pair of cones joined...

.
Ursa Minor is colloquially known as the Little Dipper because its seven brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s seem to form the shape of a dipper (ladle
Ladle (spoon)
A ladle is a type of spoon used to scoop up and serve soup, stew, or other foods. Although designs vary, a typical ladle has a long handle terminating in a deep bowl, frequently with the bowl oriented at an angle to the handle to facilitate lifting liquid out of a pot or other vessel and conveying...

 or scoop).
Encyclopedia
Ursa Minor also known as the Little Bear, is a constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 in the northern sky. Like the Great Bear
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...

, the tail of the Little Bear may also be seen as the handle of a ladle, whence the name Little Dipper. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

, and remains one of the 88 modern constellations. Ursa Minor is notable as the location of the north celestial pole
Celestial pole
The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere...

, although this will change after some centuries due to the precession of the equinoxes
Precession of the equinoxes
In astronomy, axial precession is a gravity-induced, slow and continuous change in the orientation of an astronomical body's rotational axis. In particular, it refers to the gradual shift in the orientation of Earth's axis of rotation, which, like a wobbling top, traces out a pair of cones joined...

.

Stars

Ursa Minor is colloquially known as the Little Dipper because its seven brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s seem to form the shape of a dipper (ladle
Ladle (spoon)
A ladle is a type of spoon used to scoop up and serve soup, stew, or other foods. Although designs vary, a typical ladle has a long handle terminating in a deep bowl, frequently with the bowl oriented at an angle to the handle to facilitate lifting liquid out of a pot or other vessel and conveying...

 or scoop). The star at the end of the dipper handle is Polaris
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....

, 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
Big Dipper
The Plough, also known as the Big Dipper or the Saptarishi , is an asterism of seven stars that has been recognized as a distinct grouping in many cultures from time immemorial...

, a nearby asterism
Asterism (astronomy)
In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one. Like constellations, asterisms are in most cases composed of stars which, while they are visible in the same general direction,...

 found in the constellation Ursa Major
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...

.

The four stars constituting the "bowl" of the little dipper are unusual in that they are of second, third, fourth and, fifth magnitudes. Hence, they provide an easy guide to determining what magnitude stars are visible, useful for city dwellers or testing one's eyesight.

The six named stars of Ursa Minor are the following:
Proper
Name
Bayer
Designation
Apparent
Magnitude
Distance
(LY)
  Polaris (north star)      α UMi        2.02      430
  Kochab      β UMi
Beta Ursae Minoris
Beta Ursae Minoris is the second brightest star in the bowl of the "Little Dipper,"the constellation Ursa Minor. It has the traditional name Kochab. Kochab's magnitude is 2.07. It is 16 degrees from Polaris. The star is an orange giant and is 126.4 ± 2.5 light years from Earth. It is 130 times...

 
      2.07      126
  Pherkad      γ UMi
Gamma Ursae Minoris
Gamma Ursae Minoris is a slightly variable star in the constellation Ursa Minor. It also has the common name Pherkad. Together with Beta Ursae Minoris, Gamma forms the end of the dipper pan of the "Little Dipper"...

 
      3.00      480
  Yildun      δ UMi
Delta Ursae Minoris
Delta Ursae Minoris is a star in the constellation Ursa Minor. It has the traditional name Yildun , from the Turkish yıldız "star"...

 
      4.85      185
  Ahfa al Farkadain      ζ UMi
Zeta Ursae Minoris
Zeta Ursae Minoris is a star in the constellation Ursa Minor. It has the traditional name Akhfa al Farkadain, from the Arabic أخفى الفرقدين aḫfa al-farqadayn "the dimmer of the two calves", as opposed to Anwar al Farkadain "the brighter of the two calves"...

 
      4.32      376
  Anwar al Farkadain      η UMi
Eta Ursae Minoris
Eta Ursae Minoris is a star in the constellation Ursa Minor. It has the traditional names Anwar al Farkadain and Alasco...

 
      4.95        97


Polaris
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....

 (α UMi), the brightest star in the constellation, is a 'yellow-white' supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...

 shining at 2.02 apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 . It belongs to the rare class of Cepheid
Cepheid variable
A Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...

 variable star
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...

s.
Kochab (β UMi) is only slightly less bright than Polaris. It is a 2.08 orange giant star, 16 degrees from Polaris.
Kochab 126.4 ± 2.5 light years from the Sun, and is 130 times more luminous than the Sun, at a surface temperature of approximately 4,000 K.

Deep sky objects

Ursa Minor Dwarf
Ursa Minor Dwarf
The Ursa Minor Dwarf dwarf elliptical galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. It is part of the Ursa Minor constellation, and a satellite galaxy to the Milky Way...

, a dwarf galaxy
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...

, is located in the area of the constellation.

History and mythology

Ursa Minor is commonly visualized as a baby bear with an unusually long tail.

Ursa Minor and Ursa Major
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...

 were related by the Greeks to the myth of Callisto
Callisto (mythology)
In Greek mythology, Callisto or Kallisto was a nymph of Artemis. Transformed into a bear and set among the stars, she was the bear-mother of the Arcadians, through her son Arcas.-Origin of the myth:...

 and Arcas
Arcas
In Greek mythology, Arcas was the son of Zeus and Callisto. Callisto was a nymph in the retinue of the goddess Artemis. Zeus, being a flirtatious god, wanted Callisto for a lover. As she would not be with anyone but Artemis, Zeus cunningly disguised himself as Artemis and seduced Callisto...

. However, in a variant of the story, in which it is Boötes
Boötes
Boötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from the Greek Βοώτης, Boōtēs, meaning herdsman or plowman...

 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, the North Star.

Previously, Ursa Minor was considered to be just seven close stars, mythologically regarded as sisters. In early Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

, the seven stars of the Little Dipper were considered to be the Hesperides
Hesperides
In Greek mythology, the Hesperides are nymphs who tend a blissful garden in a far western corner of the world, located near the Atlas mountains in North Africa at the edge of the encircling Oceanus, the world-ocean....

, daughters of Atlas. Together with the nearby constellations of 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 Labours of Hercules.
In Hungarian mythology the constellation is called 'Little Goncol cart' (Göncöl szekér) after a legendary shaman. (Ursa Major is 'Big Goncol cart.') The shaman's knowledge knew no limit. He invented the cart: His nation was wandering, so the cart was the biggest gift of the Gods to the country. Legends claim he knew everything about the world. Nobody saw his death; his body simply disappeared among the stars.

Because Ursa Minor consists of seven stars, the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 word for "North
North
North is a noun, adjective, or adverb indicating direction or geography.North is one of the four cardinal directions or compass points. It is the opposite of south and is perpendicular to east and west.By convention, the top side of a map is north....

" (i.e. where Polaris points) is septentrio, from septem (seven) and trio (three), from three ox
Ox
An ox , also known as a bullock in Australia, New Zealand and India, is a bovine trained as a draft animal. Oxen are commonly castrated adult male cattle; castration makes the animals more tractable...

en driving a plow, which the seven stars also resemble.

See also

  • Ursa Major
    Ursa Major
    Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...

  • Ursa Minor Beta, a place in The Hitchhiker's Guide to the Galaxy
    The Hitchhiker's Guide to the Galaxy
    The Hitchhiker's Guide to the Galaxy is a science fiction comedy series created by Douglas Adams. Originally a radio comedy broadcast on BBC Radio 4 in 1978, it was later adapted to other formats, and over several years it gradually became an international multi-media phenomenon...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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