Big Bear, Little Bear

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Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope . Retrieved 29 November 2014. Boisse, Isabelle; Pepe, Francesco; Perrier, Christian; Queloz, Didier; Bonfils, Xavier; Bouchy, François; Santos, Nuno C.; Arnold, Luc; Beuzit, Jean-Luc; Dìaz, Rodrigo F.; Delfosse, Xavier; Eggenberger, Anne; Ehrenreich, David; Forveille, Thierry; Hébrard, Guillaume; Lagrange, Anne-Marie; Lovis, Christophe; Mayor, Michel; Moutou, Claire; Naef, Dominique; Santerne, Alexandre; Ségransan, Damien; Sivan, Jean-Pierre; Udry, Stéphane (2012), "The SOPHIE search for northern extrasolar planets V. Follow-up of ELODIE candidates: Jupiter-analogs around Sun-like stars", Astronomy and Astrophysics, 545: A55, arXiv: 1205.5835, Bibcode: 2012A&A...545A..55B, doi: 10.1051/0004-6361/201118419, S2CID 119109836 Rogers, John H. (1998). "Origins of the Ancient Constellations: II. The Mediterranean traditions". Journal of the British Astronomical Association. 108: 79–89. Bibcode: 1998JBAA..108...79R. Others have suggested that an archaic interpretation of Ursa Major was that of a cow, forming a group with Boötes as herdsman, and Ursa Minor as a dog. [13] George William Cox explained it as a variant of Λυκόσουρα, understood as "wolf's tail" but by him etymologized as "trail, or train, of light" (i.e. λύκος "wolf" vs. λύκ- "light"). Allen points to the Old Irish name of the constellation, drag-blod "fire trail", for comparison. Polaris, the brightest star in the constellation, is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging in apparent magnitude from 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab, is an aging star that has swollen and cooled to become an orange giant with an apparent magnitude of 2.08, only slightly fainter than Polaris. Kochab and 3rd-magnitude Gamma Ursae Minoris have been called the "guardians of the pole star" or "Guardians of The Pole". [3] Planets have been detected orbiting four of the stars, including Kochab. The constellation also contains an isolated neutron star— Calvera—and H1504+65, the hottest white dwarf yet discovered, with a surface temperature of 200,000 K.

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Benson, Priscilla J.; Clayton, Geoffrey C.; Garnavich, Peter; Szkody, Paula (1994). "Z Ursa Minoris – a New R Coronae Borealis Variable". The Astronomical Journal. 108 (#1): 247–50. Bibcode: 1994AJ....108..247B. doi: 10.1086/117063. Because Ursa Minor consists of seven stars, the Latin word for "north" ( i.e., where Polaris points) is septentrio, from septem (seven) and triones ( oxen), from seven oxen driving a plough, which the seven stars also resemble. This name has also been attached to the main stars of Ursa Major. [16] van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific. 112 (#770): 529–36. arXiv: astro-ph/0001040. Bibcode: 2000PASP..112..529V. doi: 10.1086/316548. S2CID 1805423. Located close to Polaris is Lambda Ursae Minoris, a red giant of spectral type M1III. It is a semiregular variable varying between magnitudes 6.35 and 6.45. [46] The northerly nature of the constellation means that the variable stars can be observed all year: The red giant R Ursae Minoris is a semiregular variable varying from magnitude 8.5 to 11.5 over 328days, while S Ursae Minoris is a long-period variable that ranges between magnitudes 8.0 and 11 over 331days. [47] Located south of Kochab and Pherkad towards Draco is RR Ursae Minoris, [3] a red giant of spectral type M5III that is also a semiregular variable ranging from magnitude 4.44 to 4.85 over a period of 43.3days. [48] T Ursae Minoris is another red-giant variable star that has undergone a dramatic change in status—from being a long-period (Mira) variable ranging from magnitude 7.8 to 15 over 310–315 days, to being a semiregular variable. [49] The star is thought to have undergone a shell helium flash—a point where the shell of helium around the star's core reaches a critical mass and ignites—marked by its abrupt change in variability in 1979. [50] Z Ursae Minoris is a faint variable star that suddenly dropped 6magnitudes in 1992 and was identified as one of a rare class of stars— R Coronae Borealis variables. [51]

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Ursa Minor is rather devoid of deep-sky objects. The Ursa Minor Dwarf, a dwarf spheroidal galaxy, was discovered by Albert George Wilson of the Lowell Observatory in the Palomar Sky Survey in 1955. [67] Its centre is around 225 000 light-years distant from Earth. [68] In 1999, Kenneth Mighell and Christopher Burke used the Hubble Space Telescope to confirm that the galaxy had had a single burst of star formation that took place around 14billion years ago and lasted around 2billion years, [69] and that the galaxy was probably as old as the Milky Way itself. [70] The tradition of naming the northern constellations "bears" appears to be genuinely Greek, although Homer refers to just a single "bear". [8] Traditionally known as Pherkad, Gamma Ursae Minoris has an apparent magnitude that varies between 3.04 and 3.09 roughly every 3.4hours. [32] It and Kochab have been termed the "guardians of the pole star". [3] A white bright giant of spectral type A3II-III, [32] with around 4.8times the Sun's mass, 1,050times its luminosity and 15times its radius, [33] it is 487±8 light-years distant from Earth. [28] Pherkad belongs to a class of stars known as Delta Scuti variables [32]—short period (six hours at most) pulsating stars that have been used as standard candles and as subjects to study asteroseismology. [34] Also possibly a member of this class is Zeta Ursae Minoris, [35] a white star of spectral type A3V, [36] which has begun cooling, expanding and brightening. It is likely to have been a B3 main-sequence star and is now slightly variable. [35] At magnitude 4.95 the dimmest of the seven stars of the Little Dipper is Eta Ursae Minoris. [37] A yellow-white main-sequence star of spectral type F5V, it is 97 light-years distant. [38] It is double the Sun's diameter, 1.4times as massive, and shines with 7.4times its luminosity. [37] Nearby Zeta lies 5.00-magnitude Theta Ursae Minoris. Located 860 ± 80light-years distant, [39] it is an orange giant of spectral type K5III that has expanded and cooled off the main sequence, and has an estimated diameter around 4.8times that of the Sun. [40]

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Zeta Ursae Minoris – Variable Star". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg . Retrieved 21 June 2014.

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The origin of this name is unclear (Ursa Minor being a "dog's tail" would imply that another constellation nearby is "the dog", but no such constellation is known). [11] Bergh, Sidney (2000). The Galaxies of the Local Group. Cambridge, UK: Cambridge University Press. p.257. ISBN 978-1-139-42965-8. Making up the handle of the Little Dipper are Delta Ursae Minoris, or Yildun, [41] and Epsilon Ursae Minoris. Just over 3.5 degrees from the north celestial pole, Delta is a white main-sequence star of spectral type A1V with an apparent magnitude of 4.35, [42] located 172±1 light-years from Earth. [28] It has around 2.8 times the diameter and 47 times the luminosity of the Sun. [43] A triple star system, [44] Epsilon Ursae Minoris shines with a combined average light of magnitude 4.22. [45] A yellow giant of spectral type G5III, [45] the primary is a RS Canum Venaticorum variable star. It is a spectroscopic binary, with a companion 0.36AU distant, and a third star—an orange main-sequence star of spectral type K0—8100AU distant. [44] Ursa Minor ( Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. Ursa Minor was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the north pole star.