View source for Astronomy:Ursa Minor

{{Short description|Constellation in the northern celestial hemisphere}}
{{Infobox constellation
| name = Ursa Minor
| abbreviation = UMi<ref name="boundary" />
| genitive = Ursae Minoris<ref name="boundary" />
| pronounce = {{ubl|{{IPAc-en|ˌ|ɜːr|s|ə|_|ˈ|m|aɪ|n|ər}}|Genitive: {{IPAc-en|ˌ|ɜːr|s|iː|_|m|ᵻ|ˈ|n|ɒ|r|ᵻ|s}}}}
| symbolism = the Little Bear<ref name="boundary" />
| RA = {{RA|00|00}} to {{RA|24|00}}<ref name="boundary" />
| dec= 65.40° to 90°<ref name="boundary" />
| family = Ursa Major
| quadrant = NQ3
| areatotal = 256
| arearank = 56th
| numbermainstars = 7
| numberbfstars = 23
| numberstarsplanets = 4
| numberbrightstars = 3
| numbernearbystars = 0
| brighteststarname = [[Astronomy:Polaris|Polaris]]<ref name=Wisc>{{cite web| title=Ursa Minor |author= Department of Astronomy |publisher= University of Wisconsin–Madison |year= 1995 |access-date=27 June 2015|url=http://www.astro.wisc.edu/~dolan/constellations/constellations/Ursa_Minor.html}}</ref>
| starmagnitude = 1.97
| neareststarname = UU UMi
| stardistancely = 42.60
| stardistancepc = 13.06
| numbermessierobjects = 0
| meteorshowers = [[Astronomy:Ursids|Ursids]]
| bordering = {{ubl|[[Astronomy:Draco (constellation)|Draco]]|[[Astronomy:Camelopardalis|Camelopardalis]]|[[Astronomy:Cepheus (constellation)|Cepheus]]}}
| latmax = [[Earth:North Pole|90]]
| latmin = 10
| month = June<ref name=Wisc />
| notes=
}}

'''Ursa Minor''' ([[Social:Latin|Latin]]: 'Lesser Bear', contrasting with [[Astronomy:Ursa Major|Ursa Major]]), also known as the '''Little Bear''', is a [[Astronomy:Constellation|constellation]] located in the far [[Astronomy:Northern celestial hemisphere|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 [[Astronomy:Big Dipper|Big Dipper]]. Ursa Minor was one of the 48 constellations listed by the 2nd-century astronomer [[Biography:Ptolemy|Ptolemy]], and remains one of the [[Astronomy:88 modern constellations|88 modern constellations]]. Ursa Minor has traditionally been important for [[Earth:Navigation|navigation]], particularly by mariners, because of [[Astronomy:Polaris|Polaris]] being the north [[Astronomy:Pole star|pole star]].

Polaris, the brightest [[Astronomy:Star|star]] in the constellation, is a yellow-white [[Astronomy:Supergiant|supergiant]] and the brightest [[Astronomy:Cepheid variable|Cepheid variable]] star in the night sky, ranging in [[Astronomy:Apparent magnitude|apparent magnitude]] from 1.97 to 2.00. [[Astronomy:Beta Ursae Minoris|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 [[Astronomy:Gamma Ursae Minoris|Gamma Ursae Minoris]] have been called the "guardians of the pole star" or "Guardians of The Pole".<ref name=Arnold99 /> Planets have been detected orbiting four of the stars, including Kochab. The constellation also contains an isolated neutron star—[[Astronomy:Calvera (X-ray source)|Calvera]]—and [[Astronomy:H1504+65|H1504+65]], the hottest [[Astronomy:White dwarf|white dwarf]] yet discovered, with a [[Astronomy:Effective temperature|surface temperature]] of 200,000 [[Kelvin|K]].

== History and mythology ==
{{anchor|History}}
[[File:Sidney Hall - Urania's Mirror - Draco and Ursa Minor.jpg|thumb|300px|Ursa Minor, with Draco looping around it, as depicted in ''[[Astronomy:Urania's Mirror|Urania's Mirror]]'',<ref>{{cite web|url=http://www.ianridpath.com/atlases/urania.html |title=Urania's Mirror c.1825 – Ian Ridpath's Antique Star Atlases |author=Ridpath, Ian |publisher=Self-published |access-date=13 February 2012}}</ref> a set of constellation maps published in London c. 1825]]
In the [[Astronomy:Babylonian star catalogues|Babylonian star catalogues]], Ursa Minor was known as the "Wagon of Heaven" ({{lang|akk|<sup>MUL</sup>MAR.GÍD.DA.AN.NA}}, also associated with the goddess Damkina). It is listed in the [[Astronomy:MUL.APIN|MUL.APIN]] catalogue, compiled around 1000&nbsp;BC, among the "Stars of [[Religion:Enlil|Enlil]]"—that is, the northern sky.<ref>{{cite journal |author=Rogers, John H. |title= Origins of the Ancient Constellations: I. The Mesopotamian Traditions  |journal=[[Organization:Journal of the British Astronomical Association|Journal of the British Astronomical Association]] |volume=108 |date=1998 |pages= 9–28 |bibcode= 1998JBAA..108....9R }}</ref>

According to [[Biography:Diogenes Laërtius|Diogenes Laërtius]], citing Callimachus, [[Biography:Thales of Miletus|Thales of Miletus]] "measured the stars of the Wagon by which the [[History:Phoenicia|Phoenicia]]ns sail". Diogenes identifies these as the constellation of Ursa Minor, which for its reported use by the Phoenicians for navigation at sea were also named ''Phoinikē''.<ref>Hermann Hunger, David Edwin Pingree, ''Astral Sciences in Mesopotamia'' (1999), [https://books.google.com/books?id=7hnTZ8tdOS0C&pg=PA68 p. 68].</ref><ref name="Albright 1972">{{cite journal|last=Albright|first=William F. |date=1972|title=Neglected Factors in the Greek Intellectual Revolution|journal=Proceedings of the American Philosophical Society |volume=116|issue=3|pages= 225–42|jstor=986117}}</ref>
The tradition of naming the northern constellations "bears" appears to be genuinely Greek, although [[Biography:Homer|Homer]] refers to just a single "bear".<ref name=ridpathUMi>{{cite web| url=http://www.ianridpath.com/startales/ursaminor.html | title=Ursa Minor |last1=Ridpath|first1=Ian|publisher=Self-published  |work=Star Tales | access-date= 7 March 2015}}
{{cite book|last=Blomberg|first=Peter E.|title=Archaeoastronomy in Archaeology and Ethnography: Papers from the Annual Meeting of SEAC (European Society for Astronomy in Culture), held in Kecskemét in Hungary in 2004|editor=Pásztor, Emília |publisher=Archaeopress|location=Oxford, UK|date=2007|pages=129–32|chapter=How Did the Constellation of the Bear Receive its Name?|isbn=978-1-4073-0081-8|chapter-url=http://minoanastronomy.mikrob.com/pdf/2007b%20Peter%20Kecs.pdf}}</ref>
The original "bear" is thus [[Astronomy:Ursa Major|Ursa Major]], and Ursa Minor was admitted as the second, or "Phoenician Bear" (Ursa Phoenicia, hence Φοινίκη, Phoenice)
only later, according to Strabo (I.1.6, C3) due to a suggestion by Thales, who suggested it as a navigation aid to the Greeks, who had been navigating by Ursa Major. In [[History:Classical antiquity|classical antiquity]], the [[Astronomy:Celestial pole|celestial pole]] was somewhat closer to [[Astronomy:Beta Ursae Minoris|Beta Ursae Minoris]] than to Alpha Ursae Minoris, and the entire constellation was taken to indicate the northern direction. Since the medieval period, it has become convenient to use Alpha Ursae Minoris (or "Polaris") as the North Star. (Even though, in the medieval period, Polaris was still several degrees away from the celestial pole.<ref name="Lang2013">{{cite book|author=Kenneth R. Lang|title=Essential Astrophysics|url=https://books.google.com/books?id=PVJEAAAAQBAJ&pg=PA10|year= 2013|publisher=Springer Science & Business Media|isbn=978-3-642-35963-7|pages=10–15}}</ref>{{efn| The position of the north celestial pole moves in accordance with the Earth's [[Astronomy:Axial precession|axial precession]] such that in 12,000 years' time, [[Astronomy:Vega|Vega]] will be the Pole Star.<ref name="Lang2013" />}} ) Now, Polaris is within 1° of the north celestial pole and remains the current [[Astronomy:Pole star|Pole star]]. Its Neo-Latin name of ''stella polaris'' was coined only in the early modern period.<ref>{{Cite web|title=Ursa Minor – Polaris|website=Star Tales|url=http://www.ianridpath.com/startales/ursaminor.html#polaris|access-date=2023-01-13}}</ref>

The ancient name of the constellation is ''Cynosura'' ([[Social:Ancient Greek|Greek]] Κυνοσούρα "dog's tail").
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).<ref name=Allen447>{{cite book|title=Star Names: Their Lore and Meaning|url=https://archive.org/details/StarNamesAndTheirMeanings|author=Allen, Richard Hinckley|date=1899}} [https://penelope.uchicago.edu/Thayer/e/gazetteer/topics/astronomy/_texts/secondary/allsta/home.html 447f.]
"The origin of this word is uncertain, for the star group does not answer to its name unless the dog himself be attached; still some, recalling a variant legend of Kallisto and her Dog instead of Arcas, have thought that here lay the explanation. Others have drawn this title from that of the Attican promontory east of Marathon, because sailors, on their approach to it from the sea, saw these stars shining above it and beyond; but if there be any connection at all here, the reversed derivation is more probable; while Bournouf asserted that it is in no way associated with the Greek word for "dog."</ref>
Instead, the mythographic tradition of ''[[Astronomy:Catasterismi|Catasterismi]]'' makes ''[[Astronomy:Cynosura (nymph)|Cynosura]]'' the name of an [[Unsolved:Oread|Oread]] [[Unsolved:Nymph|nymph]] described as a nurse of [[Religion:Zeus|Zeus]], honoured by the god with a place in the sky.<ref>[http://articles.adsabs.harvard.edu/full/1970ASPL...10..361C Condos, T., The Katasterismoi (Part 1), 1967]. Also mentioned by Servius  ''On Virgilius' Georgics'' 1. 246, c. AD 400; a mention of doubtful authenticity is Hyginus, ''De Astronomica'' 2.2.</ref>
There are various proposed explanations for the name ''Cynosura''. One suggestion connects it to the myth of [[Astronomy:Callisto (mythology)|Callisto]], with her son [[Astronomy:Arcas|Arcas]] replaced by her dog being placed in the sky by Zeus.<ref name=Allen447 />
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.<ref>[https://archive.org/stream/researchesintoo01browgoog#page/n284/mode/2up/search/Syoronos 265f. Robert Brown, ''Researches into the origin of the primitive constellations of the Greeks, Phoenicians and Babylonians'' (1899)],
"M. Syoronos (''Types Mon. des anciens'' p. 116) is of opinion that in the case of some Kretan coin-types, ''Ursa Maj.'' is represented as a Cow, hence ''Boôtês'' as 'the Herdsman', and ''Ursa Min. as a Dog'' ('Chienne'  cf. ''Kynosoura'', ''Kynoupês''), a Zeus-suckler."
A supposed Latin tradition of naming Ursa Minor ''Catuli'' "whelps" or ''Canes Laconicae'' "Spartan dogs", recorded in Johann Heinrich Alsted (1649, [https://books.google.com/books?id=KGkp6GNTCOQC&pg=PA408 408]), is probably an early modern innovation. <!--Allen: "Caesius", probably meaning Philipp von Zesen--></ref> George William Cox explained it as a variant of [[Biology:Lycosura|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 [[Social:Old Irish|Old Irish]] name of the constellation, ''drag-blod'' "fire trail", for comparison.
Brown (1899) suggested a non-Greek origin of the name (a loan from an [[Social:Akkadian language|Assyrian]] ''An‑nas-sur‑ra'' "high-rising").<ref>"Very recently, however, Brown [Robert Brown, ''Researches into the origin of the primitive constellations of the Greeks, Phoenicians and Babylonians''] has suggested that the word is not Hellenic in origin, but Euphratean; and, in confirmation of this, mentions a constellation title from that valley, transcribed by Sayce as An‑ta-sur‑ra, the Upper Sphere. Brown reads this An‑nas-sur‑ra, High in Rising, certainly very appropriate to Ursa Minor; and he compares it with Κ‑υν‑όσ‑ου‑ρα, or, the initial consonant being omitted, Unosoura." (Allen, Richard Hinckley. "Star Names: Their Lore and Meaning." New York, Dover Editions, 1963, p.&nbsp;448.)
Brown points out that Aratus fittingly describes "Cynosura" as "high-running" ("at the close of night Cynosura's head runs very high",  κεφαλὴ Κυνοσουρίδος ἀκρόθι νυκτὸς
ὕψι μάλα τροχάει v. 308f).</ref>

An alternative myth tells of two bears that saved Zeus from his murderous father [[Religion:Cronus|Cronus]] by hiding him on [[Religion:Mount Ida (Crete)|Mount Ida]]. Later Zeus set them in the sky, but their tails grew long from their being swung up into the sky by the god.<ref name=RogersII>{{cite journal| author=Rogers, John H. |title= Origins of the Ancient Constellations: II. The Mediterranean traditions |journal=Journal of the British Astronomical Association |volume=108 |date=1998|pages= 79–89|bibcode = 1998JBAA..108...79R}}</ref>

Because Ursa Minor consists of seven stars, the [[Social:Latin|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.<ref name=wagman>{{cite book | last = Wagman | first = Morton | date = 2003 | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others | publisher = The McDonald & Woodward Publishing Company | location = Blacksburg, Virginia | isbn = 978-0-939923-78-6 |pages=312, 518}}</ref><!-- cites 2 previous sentences -->

In [[Unsolved:Inuit astronomy|Inuit astronomy]], the three brightest stars—Polaris, Kochab and Pherkad—were known as ''Nuutuittut'' "never moving", though the term is more frequently used in the singular to refer to Polaris alone. The Pole Star is too high in the sky at far northern latitudes to be of use in navigation.<ref>{{cite book | last = MacDonald | first = John | date = 1998 | title = The Arctic Sky: Inuit Astronomy, Star Lore, and Legend | url = https://archive.org/details/arcticskyinuitas0000macd | url-access = registration | publisher = Royal Ontario Museum/Nunavut Research Institute |location=Toronto, Ontario | isbn = 978-0-88854-427-8 |page=[https://archive.org/details/arcticskyinuitas0000macd/page/61 61]}}</ref> In Chinese astronomy, the main stars of Ursa Minor are divided between two [[Astronomy:Chinese constellations|asterisms]]:
勾陳 ''Gòuchén'' (Curved Array) (including α UMi, [[Astronomy:Delta Ursae Minoris|δ UMi]], [[Astronomy:Epsilon Ursae Minoris|ε UMi]], [[Astronomy:Zeta Ursae Minoris|ζ UMi]], [[Astronomy:Eta Ursae Minoris|η UMi]], [[Astronomy:Theta Ursae Minoris|θ UMi]], [[Astronomy:Lambda Ursae Minoris|λ UMi]]) and
北極 ''Běijí'' (Northern Pole) (including β UMi and [[Astronomy:Gamma Ursae Minoris|γ UMi]]).<!--The boundaries of the modern IAU constellation are also touched upon by the asterisms 天床 ''Tiānchuáng'' (Celestial Bed, mostly in [[Astronomy:Draco (constellation)|Draco]]) and 四輔 ''Sìfǔ'' (Four Advisors, mostly in [[Astronomy:Camelopardalis|Camelopardalis]]).--><ref>{{Cite web|title=Ursa Minor – Chinese associations|website=Star Tales|url=http://www.ianridpath.com/startales/ursaminor.html#chinese|access-date=2023-01-13}}</ref>

== Characteristics ==
Ursa Minor is bordered by [[Astronomy:Camelopardalis|Camelopardalis]] to the west, [[Astronomy:Draco (constellation)|Draco]] to the west, and Cepheus to the east. Covering 256&nbsp;square degrees, it ranks 56th of the 88 constellations in size. Ursa Minor is colloquially known in the US as the Little Dipper because its seven brightest stars seem to form the shape of a dipper (ladle or scoop). The star at the end of the dipper handle is Polaris. Polaris can also be found by following a line through the two stars—[[Astronomy:Alpha Ursae Majoris|Alpha]] and [[Astronomy:Beta Ursae Majoris|Beta Ursae Majoris]], popularly called the Pointers—that form the end of the "bowl" of the Big Dipper, for 30 degrees (three upright fists at arms' length) across the night sky.<ref name=omeara1998>{{cite book | author=O'Meara, Stephen James | title=The Messier Objects | series=Deep-sky Companions | publisher=Cambridge University Press |location=Cambridge, UK| year=1998 | isbn=978-0-521-55332-2 | url=https://archive.org/details/messierobjectsfi00omea | url-access=registration | page=[https://archive.org/details/messierobjectsfi00omea/page/10 10]}}</ref> The four stars constituting the bowl of the Little Dipper are of second, third, fourth, and fifth magnitudes, respectively, and provide an easy guide to determining what magnitude stars are visible, useful for city dwellers or testing one's eyesight.<ref>{{cite book | author=Olcott, William Tyler |  title=Star Lore of All Ages: A Collection of Myths, Legends, and Facts Concerning the Constellations of the Northern Hemisphere | publisher=Courier Corporation |location=New York, New York | date=2012 | orig-year=1911 | page=377 | url=https://books.google.com/books?id=ODJM51UvfzEC&pg=PA377| isbn=978-0-486-14080-3 }}</ref><!-- cites previous two sentences -->

The three-letter abbreviation for the constellation, as adopted by the IAU ([[Organization:International Astronomical Union|International Astronomical Union]]) in 1922, is "UMi".<ref name="pa30_469">{{cite journal | last=Russell | first=Henry Norris | title=The New International Symbols for the Constellations | journal=Popular Astronomy | volume=30 | page=469 | bibcode=1922PA.....30..469R | date=1922}}</ref> The official constellation boundaries, as set by Belgian astronomer [[Biography:Eugène Joseph Delporte|Eugène Delporte]] in 1930, are defined by a polygon of 22 segments (''illustrated in infobox''). In the [[Astronomy:Equatorial coordinate system|equatorial coordinate system]], the [[Right ascension|right ascension]] coordinates of these borders lie between {{RA|08|41.4}} and {{RA|22|54.0}}, while the [[Declination|declination]] coordinates range from the north celestial pole to 65.40° in the south.<ref name="boundary">{{Cite journal | title=Ursa Minor, Constellation Boundary | journal=The Constellations | publisher=International Astronomical Union | url=https://www.iau.org/public/themes/constellations/#umi | access-date=12 May 2014}}</ref> Its position in the far northern celestial hemisphere means that the whole constellation is visible only to observers in the northern hemisphere.<ref name=tirionconst>{{cite web| url=http://www.ianridpath.com/constellations2.html | title=Constellations: Lacerta–Vulpecula | work= Star Tales |author=Ridpath, Ian |publisher=Self-published | access-date= 21 June 2014}}</ref>{{efn|1=While parts of the constellation technically rise above the horizon to observers between the equator and 24°S, stars within a few degrees of the horizon are to all intents and purposes unobservable.<ref name=tirionconst />}}

== Features ==
[[File:UrsaMinorCC.jpg|thumb|left|200px|The constellation Ursa Minor as it can be seen by the naked eye (with connections and label added). Notice the seven stars of Ursa Major that form the Big Dipper and then make a line from the outermost Big Dipper stars (sometimes called the "pointers") to Polaris.]]

=== Stars ===
The German cartographer Johann Bayer used the Greek letters alpha to [[Biology:Theta|theta]] to label the most prominent stars in the constellation, while his countryman Johann Elert Bode subsequently added iota through phi. Only lambda and pi remain in use, likely because of their proximity to the north celestial pole.<ref name=wagman /> Within the constellation's borders, there are 39&nbsp;stars brighter than or equal to [[Astronomy:Apparent magnitude|apparent magnitude]]&nbsp;6.5.<ref name=tirionconst />{{efn|1=Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.<ref>{{cite web|url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|title=The Bortle Dark-Sky Scale|last=Bortle|first=John E.|date=February 2001|work=Sky & Telescope|access-date=29 November 2014}}</ref>}}

Marking the Little Bear's tail,<ref name=wagman /> [[Astronomy:Polaris|Polaris]], or Alpha Ursae Minoris, is the brightest star in the constellation, varying between apparent magnitudes 1.97 and 2.00 over a period of 3.97&nbsp;days.<ref name=AAVSOpol /> Located around 432&nbsp;[[Astronomy:Light-year|light-year]]s away from Earth,<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alf+UMi&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Alpha Ursae Minoris – Classical Cepheid (Delta Cep Type) |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 19 August 2014}}</ref> it is a yellow-white [[Astronomy:Supergiant|supergiant]] that varies between spectral types F7Ib and F8Ib,<ref name=AAVSOpol>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37413 |title=Alpha Ursae Minoris |author=Otero, Sebastian Alberto |date=4 December 2007 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=16 May 2014}}</ref> and has around 6&nbsp;times the Sun's mass, 2,500&nbsp;times its luminosity, and 45&nbsp;times its radius. Polaris is the brightest [[Astronomy:Cepheid variable|Cepheid]] [[Astronomy:Variable star|variable star]] visible from Earth. It is a triple star system, the supergiant primary star having two [[Astronomy:F-type main-sequence star|yellow-white main-sequence star]] companions that are 17 and 2,400&nbsp;[[Astronomy:Astronomical unit|astronomical unit]]s (AU) distant and take 29.6 and 42,000&nbsp;years respectively to complete one orbit.<ref name=kaleralpha>{{cite web| first1=James B. | last1=Kaler | title=Polaris | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/polaris.html | access-date=19 August 2014}}</ref>

Traditionally called Kochab, Beta Ursae Minoris, at apparent magnitude 2.08, is slightly less bright than Polaris.<ref name=simbadbeta /> Located around 131&nbsp;light-years away from Earth,<ref name="vanLeeuwen2007">{{cite journal | first=F. | last=van Leeuwen | title=Validation of the New Hipparcos Reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–64 | date=2007 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | arxiv=0708.1752| s2cid=18759600 }}</ref>{{efn|1=Or more specifically 130.9±0.6&nbsp;light-years by parallax measurement.<ref name="vanLeeuwen2007" />}} it is an orange giant—an evolved star that has used up the hydrogen in its core and moved off the [[Astronomy:Main sequence|main sequence]]—of spectral type K4III.<ref name=simbadbeta>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Bet+UMi&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Beta Ursae Minoris – Variable Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 18 May 2014}}</ref> Slightly variable over a period of 4.6&nbsp;days, Kochab has had its mass estimated at 1.3&nbsp;times that of the Sun via measurement of these oscillations.<ref name=aaa483_3_L43>{{cite journal  | last1 = Tarrant | first1 = N.J. | last2 = Chaplin| first2 = W.J.| last3 = Elsworth| first3 = Y.| last4 = Spreckley | first4 = S.A.| last5 = Stevens| first5 = I.R.| title = Oscillations in ß Ursae Minoris. Observations with SMEI | journal = Astronomy and Astrophysics | volume = 483 | issue = #3 | pages = L43–L46  |date=June 2008 | doi = 10.1051/0004-6361:200809738 | bibcode = 2008A&A...483L..43T | arxiv = 0804.3253 | s2cid = 53546805 }}</ref> Kochab is 450 times more luminous than the Sun and has 42 times its diameter, with a surface temperature of approximately 4,130&nbsp;K.<ref name=kalerbeta>{{cite web| first1=James B. | last1=Kaler | title=Kochab | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/kochab.html | access-date=19 August 2014}}</ref> Estimated to be around 2.95&nbsp;billion years old, ±1&nbsp;billion years, Kochab was announced to have a planetary companion around 6.1&nbsp;times as massive as [[Astronomy:Jupiter|Jupiter]] with an orbit of 522&nbsp;days.<ref>{{cite journal |title=Planetary Companions in K giants β Cancri, μ Leonis, and β Ursae Minoris | author=Lee, B.-C. | author2=Han, I. | author3=Park, M.-G. | author4=Mkrtichian, D.E. | author5=Hatzes, A.P. | author6=Kim, K.-M.| journal = Astronomy and Astrophysics| volume = 566| id=A67 | pages=7 | date = 2014| doi =10.1051/0004-6361/201322608 | bibcode=2014A&A...566A..67L|arxiv = 1405.2127 | s2cid=118631934 }}</ref>

[[File:Ursa Major - Ursa Minor - Polaris.jpg|thumb|300px|Ursa Minor and Ursa Major in relation to Polaris]]
Traditionally known as Pherkad, Gamma Ursae Minoris has an apparent magnitude that varies between 3.04 and 3.09 roughly every 3.4&nbsp;hours.<ref name=AAVSOgam>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37414 |title=Gamma Ursae Minoris |author=Watson, Christopher |date=4 January 2010 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=18 May 2014}}</ref> It and Kochab have been termed the "guardians of the pole star".<ref name=Arnold99 /> A white bright giant of spectral type A3II-III,<ref name=AAVSOgam /> with around 4.8&nbsp;times the Sun's mass, 1,050&nbsp;times its luminosity and 15&nbsp;times its radius,<ref name=kalergamma>{{cite web| first1=James B. | last1=Kaler | title=Pherkad | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/pherkad.html | access-date=18 May 2014 |date=20 December 2013}}</ref> it is 487±8 light-years distant from Earth.<ref name="vanLeeuwen2007" /> Pherkad belongs to a class of stars known as [[Astronomy:Delta Scuti variable|Delta Scuti variable]]s<ref name=AAVSOgam />—short period (six hours at most) pulsating stars that have been used as [[Astronomy:Cosmic distance ladder#Standard candles|standard candles]] and as subjects to study [[Astronomy:Asteroseismology|asteroseismology]].<ref>{{cite web|url=http://www.aavso.org/vsots_delsct|title=Delta Scuti and the Delta Scuti Variables|last=Templeton|first=Matthew |date=16 July 2010|work=Variable Star of the Season|publisher=AAVSO (American Association of Variable Star Observers)|access-date=19 August 2014}}</ref> Also possibly a member of this class is [[Astronomy:Zeta Ursae Minoris|Zeta Ursae Minoris]],<ref name=kalerzet /> a white star of spectral type A3V,<ref name=SIMBADzet>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Zet+UMi&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Zeta Ursae Minoris – Variable Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 21 June 2014}}</ref> which has begun cooling, expanding and brightening. It is likely to have been a B3 main-sequence star and is now slightly variable.<ref name=kalerzet>{{cite web| first1=James B. | last1=Kaler | title=Alifa al Farkadain | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/alifa.html | access-date=21 June 2014}}</ref> At magnitude 4.95 the dimmest of the seven stars of the Little Dipper is [[Astronomy:Eta Ursae Minoris|Eta Ursae Minoris]].<ref name=kalereta /> A yellow-white main-sequence star of spectral type F5V, it is 97 light-years distant.<ref name=SIMBADeta>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Eta+Ursae+Minoris&submit=SIMBAD+search |title = Eta Ursae Minoris |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 30 July 2014}}</ref> It is double the Sun's diameter, 1.4&nbsp;times as massive, and shines with 7.4&nbsp;times its luminosity.<ref name=kalereta>{{cite web| first1=James B. | last1=Kaler | title=Anwar al Farkadain | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/anwar.html | access-date=21 June 2014}}</ref> Nearby Zeta lies 5.00-magnitude [[Astronomy:Theta Ursae Minoris|Theta Ursae Minoris]]. Located 860 ± 80&nbsp;light-years distant,<ref name=SIMBADtet>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Theta+Ursae+Minoris&submit=SIMBAD+search |title = Theta Ursae Minoris – Variable Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 30 July 2014}}</ref> it is an orange giant of spectral type K5III that has expanded and cooled off the main sequence, and has an estimated diameter around 4.8&nbsp;times that of the Sun.<ref name=aaa367_521>{{cite journal | last1=Pasinetti Fracassini | first1=L. E. | last2=Pastori | first2=L. | last3=Covino | first3=S. | last4=Pozzi | first4=A. | title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) – Third edition – Comments and statistics | journal=Astronomy and Astrophysics | volume=367 | pages=521–24 |date=February 2001 | issue=2 | doi=10.1051/0004-6361:20000451 | bibcode=2001A&A...367..521P | arxiv=astro-ph/0012289| s2cid=425754 }}</ref>

Making up the handle of the Little Dipper are [[Astronomy:Delta Ursae Minoris|Delta Ursae Minoris]], or Yildun,<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=8 August 2018}}</ref> and [[Astronomy:Epsilon Ursae Minoris|Epsilon Ursae Minoris]]. Just over 3.5 degrees from the north celestial pole, Delta is a [[Astronomy:A-type main-sequence star|white main-sequence star]] of spectral type [[Astronomy:Stellar classification|A1V]] with an apparent magnitude of 4.35,<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Delta+UMi&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Delta Ursae Minoris |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 21 June 2014}}</ref> located 172±1 light-years from Earth.<ref name="vanLeeuwen2007" /> It has around 2.8 times the diameter and 47 times the luminosity of the Sun.<ref name=kalerdel>{{cite web| first1=James B. | last1=Kaler | title=Yildun | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/yildun.html | access-date=30 July 2014}}</ref> A triple star system,<ref name=kalereps>{{cite web| first1=James B. | last1=Kaler | title=Epsilon Ursae Minoris | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/epsumi.html | access-date=21 June 2014}}</ref> Epsilon Ursae Minoris shines with a combined average light of magnitude 4.22.<ref name=SIMBADeps>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Eps+UMi&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Epsilon Ursae Minoris – Variable of RS CVn type |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 21 June 2014}}</ref> A yellow giant of spectral type G5III,<ref name=SIMBADeps /> the primary is a [[Astronomy:RS Canum Venaticorum variable|RS Canum Venaticorum variable]] star. It is a spectroscopic binary, with a companion 0.36&nbsp;AU distant, and a third star—an orange main-sequence star of spectral type K0—8100&nbsp;AU distant.<ref name=kalereps />

Located close to Polaris is [[Astronomy:Lambda Ursae Minoris|Lambda Ursae Minoris]], a [[Astronomy:Red giant|red giant]] of spectral type M1III. It is a semiregular variable varying between magnitudes 6.35 and 6.45.<ref name=AAVSOlam>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37416 |title=Lambda Ursae Minoris |author=Watson, Christopher |date=4 January 2010 |work=The International Variable Star Index|publisher=American Association of Variable Star Observers|access-date=21 June 2014}}</ref> The northerly nature of the constellation means that the variable stars can be observed all year: The red giant [[Astronomy:R Ursae Minoris|R Ursae Minoris]] is a semiregular variable varying from magnitude 8.5 to 11.5 over 328&nbsp;days, while [[Astronomy:S Ursae Minoris|S Ursae Minoris]] is a long-period variable that ranges between magnitudes 8.0 and 11 over 331&nbsp;days.<ref name="Levy 1998">{{cite book|last=Levy|first=David H.|title=Observing Variable Stars: A Guide for the Beginner|publisher=Cambridge University Press|location=Cambridge, UK|date=1998|page=133|isbn=978-0-521-62755-9|url=https://books.google.com/books?id=5-O2cd937FMC&pg=PA133}}</ref> Located south of Kochab and Pherkad towards Draco is [[Astronomy:RR Ursae Minoris|RR Ursae Minoris]],<ref name=Arnold99>{{cite book|author=Arnold, H. J. P.|author2= Doherty, Paul|author3= Moore, Patrick |title=The Photographic Atlas of the Stars|publisher=CRC Press|location=Boca Raton, Florida|date=1999|page=148|isbn=978-0-7503-0654-6|url=https://books.google.com/books?id=YjcvJUfnWBAC&pg=PA148}}</ref> 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 43.3&nbsp;days.<ref name=AAVSOrr>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37384 |title=RR Ursae Minoris |author=Otero, Sebastian Alberto |date=16 November 2009 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=18 May 2014}}</ref> [[Astronomy:T Ursae Minoris|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.<ref name="Uttenthaler">{{cite journal|author=Uttenthaler, S.|author2=van Stiphout, K.|author3=Voet, K.|author4=van Winckel, H.|author5=van Eck, S.|author6=Jorissen, A.|author7=Kerschbaum, F.|author8=Raskin, G.|author9=Prins, S.|author10=Pessemier, W.|author11=Waelkens, C.|author12=Frémat, Y.|author13=Hensberge, H.|author14=Dumortier, L.|author15=Lehmann, H.|date=2011|title=The Evolutionary State of Miras with Changing Pulsation Periods|journal=Astronomy and Astrophysics|volume=531|pages=A88|bibcode=2011A&A...531A..88U|arxiv = 1105.2198 |doi = 10.1051/0004-6361/201116463 |s2cid=56226953}}</ref> The star is thought to have undergone a [[Astronomy:Helium flash#shell helium flash|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.<ref name="mattei95">{{cite journal|author=Mattei, Janet A.|author2=Foster, Grant|date=1995|title=Dramatic Period Decrease in T Ursae Minoris|journal=The Journal of the American Association of Variable Star Observers|volume=23|issue=2|pages=106–16|bibcode=1995JAVSO..23..106M}}</ref> [[Astronomy:Z Ursae Minoris|Z Ursae Minoris]] is a faint variable star that suddenly dropped 6&nbsp;magnitudes in 1992 and was identified as one of a rare class of stars—[[Astronomy:R Coronae Borealis variable|R Coronae Borealis variable]]s.<ref>{{cite journal|author= Benson, Priscilla J.|author2= Clayton, Geoffrey C.|author3= Garnavich, Peter|author4= Szkody, Paula |title= Z Ursa Minoris – a New R Coronae Borealis Variable |journal= [[Astronomy:The Astronomical Journal|The Astronomical Journal]] | volume= 108|issue= #1| pages= 247–50 | date=1994 |bibcode=1994AJ....108..247B|doi = 10.1086/117063 |doi-access= free}}</ref>

Eclipsing variables are star systems that vary in brightness because of one star passing in front of the other rather than from any intrinsic change in luminosity. [[Astronomy:W Ursae Minoris|W Ursae Minoris]] is one such system, its magnitude ranging from 8.51 to 9.59 over 1.7 days.<ref name=AAVSOW>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37380 |title=W Ursae Minoris |author=Watson, Christopher |date=4 January 2010  |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=18 July 2015}}</ref> The combined spectrum of the system is A2V, but the masses of the two component stars are unknown. A slight change in the orbital period in 1973 suggests there is a third component of the multiple star system—most likely a [[Astronomy:Red dwarf|red dwarf]]—with an orbital period of 62.2±3.9 years.<ref>{{cite journal | title=Period Analysis of Three Close Binary Systems: TW And, TT Her and W UMi |author1=Kreiner, J. M. |author2=Pribulla, T. |author3=Tremko, J. |author4=Stachowski, G. S. |author5=Zakrzewski, B. | journal =Monthly Notices of the Royal Astronomical Society | volume = 383 | issue = #4 |pages= 1506–12|date=2008 |doi=10.1111/j.1365-2966.2007.12652.x |bibcode=2008MNRAS.383.1506K|doi-access=free }}</ref> [[Astronomy:RU Ursae Minoris|RU Ursae Minoris]] is another example, ranging from 10 to 10.66 over 0.52&nbsp;days.<ref name=AAVSOru>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37387 |title=RU Ursae Minoris |author=Watson, Christopher |date=4 January 2010  |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=18 July 2015}}</ref> It is a [[Astronomy:Semidetached binary|semidetached]] system, as the secondary star is filling its [[Physics:Roche lobe|Roche lobe]] and transferring matter to the primary.<ref name="Manimanis">{{cite journal|title=A Photometric Study of the Near-contact System RU Ursae Minoris |author1=Manimanis, V. N. |author2=Niarchos, P. G. | journal=Astronomy and Astrophysics |volume=369 |issue=3 |pages=960–64 |date=2001|doi=10.1051/0004-6361:20010178 |bibcode=2001A&A...369..960M|doi-access=free }}</ref>

[[Astronomy:RW Ursae Minoris|RW Ursae Minoris]] is a cataclysmic variable star system that flared up as a [[Astronomy:Nova|nova]] in 1956, reaching magnitude 6. In 2003, it was still two magnitudes brighter than its baseline, and dimming at a rate of 0.02 magnitude a year. Its distance has been calculated as 5,000±800&nbsp;parsecs (16,300&nbsp;light-years), which puts its location in the [[Astronomy:Galactic halo|galactic halo]].<ref name=bianchini2003>{{cite journal |title = RW Ursae Minoris (1956): An Evolving Postnova System |author =Bianchini, A. |author2 =Tappert, C. |author3 = Canterna, R. |author4 =Tamburini, F. |author5 =Osborne, H. |author6 =Cantrell, K. |journal= Publications of the Astronomical Society of the Pacific |volume =115 |issue= #809 | pages = 811–18 | bibcode=2003PASP..115..811B|doi = 10.1086/376434 |year =2003 |doi-access =free }}</ref>

Taken from the villain in ''The Magnificent Seven'', [[Astronomy:Calvera (X-ray source)|Calvera]] is the nickname given to an [[Astronomy:Astrophysical X-ray source|X-ray source]] known as 1RXS J141256.0+792204 in the ''[[Astronomy:ROSAT|ROSAT]] All-Sky Survey Bright Source Catalog'' (RASS/BSC).<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/science/nature/6955769.stm|title=Rare Dead Star Found Near Earth|publisher=BBC |work= BBC News: Science/Nature |date=20 August 2007|access-date=21 August 2007|archive-date=13 July 2014 |archive-url=https://web.archive.org/web/20140713133234/http://news.bbc.co.uk/2/hi/science/nature/6955769.stm|url-status=live}}</ref> It has been identified as an isolated [[Astronomy:Neutron star|neutron star]], one of the closest of its kind to Earth.<ref>{{cite journal| author=Rutledge, Robert| author2=Fox, Derek| author3=Shevchuk, Andrew |date=2008 |title=Discovery of an Isolated Compact Object at High Galactic Latitude | journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]]| volume= 672| issue= #2 |pages= 1137–43 |bibcode=2008ApJ...672.1137R|arxiv = 0705.1011 |doi = 10.1086/522667 | s2cid=7915388}}</ref> Ursa Minor has two enigmatic [[Astronomy:White dwarf|white dwarf]]s. Documented on January 27, 2011, [[Astronomy:H1504+65|H1504+65]] is a faint (magnitude 15.9) star with the hottest surface temperature—200,000 K—yet discovered for a white dwarf. Its atmosphere, composed of roughly half carbon, half oxygen and 2% neon, is devoid of hydrogen and helium—its composition unexplainable by current models of stellar evolution.<ref>{{cite journal|last=Werner|first=K.|author2=Rauch, T.|date=2011|title=UV Spectroscopy of the Hot Bare Stellar Core H1504+65 with the HST Cosmic Origins Spectrograph|journal=[[Physics:Astrophysics and Space Science|Astrophysics and Space Science]]|volume=335|issue=1|pages=121–24|doi=10.1007/s10509-011-0617-x|bibcode = 2011Ap&SS.335..121W |s2cid=116910726}}</ref> [[Astronomy:WD 1337+705|WD 1337+705]] is a cooler white dwarf that has magnesium and silicon in its spectrum, suggesting a companion or circumstellar disk, though no evidence for either has come to light.<ref>{{cite journal|author1=Dickinson, N. J. |author2=Barstow, M. A. |author3=Welsh, B. Y. |author4=Burleigh, M. |author5=Farihi, J. |author6=Redfield, S. |author7=Unglaub, K. |date=2012|title=The Origin of Hot White Dwarf Circumstellar Features|journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] |volume=423|issue=2|pages=1397–1410| doi=10.1111/j.1365-2966.2012.20964.x |bibcode=2012MNRAS.423.1397D|arxiv = 1203.5226 |s2cid=119212643 }}</ref> [[Astronomy:WISE 1506+7027|WISE 1506+7027]] is a [[Astronomy:Brown dwarf|brown dwarf]] of spectral type T6 that is a mere {{val|11.1|+2.3|-1.3}} light-years away from Earth.<ref name="Marsh2013">{{cite journal | last=Marsh |first=Kenneth A. | author2=Wright, Edward L. | author3=Kirkpatrick, J. Davy | author4=Gelino, Christopher R. | author5=Cushing, Michael C. | author6=Griffith, Roger L. | author7=Skrutskie, Michael F. | author8=Eisenhardt, Peter R. | date=2013 | title=Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T | journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] | volume=762 | issue=2 | pages=119 | arxiv=1211.6977 | bibcode=2013ApJ...762..119M | doi=10.1088/0004-637X/762/2/119|s2cid=42923100 }}</ref> A faint object of magnitude 14, it was discovered by the [[Astronomy:Wide-field Infrared Survey Explorer|Wide-field Infrared Survey Explorer]] (WISE) in 2011.<ref name="Kirkpatrick2011">{{cite journal |doi=10.1088/0067-0049/197/2/19 |last1=Kirkpatrick |first1=J. Davy |last2=Cushing |first2=Michael C. |last3=Gelino |first3=Christopher R. |last4=Griffith |first4=Roger L. |last5=Skrutskie |first5=Michael F. |last6=Marsh |first6=Kenneth A. |last7=Wright |first7=Edward L. |last8=Mainzer |first8=Amy K. |last9=Eisenhardt |first9=Peter R. |last10=McLean |first10=Ian S. |last11=Thompson |first11=Maggie A. |last12=Bauer |first12=James M. |last13=Benford |first13=Dominic J. |last14=Bridge |first14=Carrie R. |last15=Lake |first15=Sean E. |last16=Petty |first16=Sara M. |last17=Stanford |first17=Spencer Adam |last18=Tsai |first18=Chao-Wei |last19=Bailey |first19=Vanessa |last20=Beichman |first20=Charles A. |last21=Bloom |first21=Joshua S. |last22=Bochanski |first22=John J. |last23=Burgasser |first23=Adam J. |last24=Capak |first24=Peter L. |last25=Cruz |first25=Kelle L. |last26=Hinz |first26=Philip M. |last27=Kartaltepe |first27=Jeyhan S. |last28=Knox |first28=Russell P. |last29=Manohar |first29=Swarnima |last30=Masters |first30=Daniel |last31=Morales-Calderon |first31=Maria |last32=Prato |first32=Lisa A. |last33=Rodigas |first33=Timothy J. |last34=Salvato |first34=Mara |last35=Schurr |first35=Steven D. |last36=Scoville |first36=Nicholas Z. |last37=Simcoe |first37=Robert A. |last38=Stapelfeldt |first38=Karl R. |last39=Stern |first39=Daniel |last40=Stock |first40=Nathan D. |last41=Vacca |first41=William D. |title=The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE) |date=2011 |journal=The Astrophysical Journal Supplement |volume=197 |issue=2 |pages=19 |arxiv=1108.4677v1 |bibcode=2011ApJS..197...19K |s2cid=16850733 }}</ref>

Kochab aside, three more stellar systems have been discovered to contain planets. [[Astronomy:11 Ursae Minoris|11 Ursae Minoris]] is an orange giant of spectral type K4III around 1.8&nbsp;times as massive as the Sun. Around 1.5&nbsp;billion years old, it has cooled and expanded since it was an A-type main-sequence star. Around 390 light-years distant, it shines with an apparent magnitude of 5.04. A planet around 11 times the mass of Jupiter was discovered in 2009 orbiting the star with a period of 516 days.<ref name="Döllinger2009">{{cite journal | title=Planetary Companions around the K Giant Stars 11 Ursae Minoris and HD 32518 | last1=Döllinger | first1=M. P. | last2=Hatzes | first2=A.P. | last3=Pasquini | first3=L. | last4=Guenther | first4=E. W. | last5=Hartmann | first5=M. | journal=Astronomy and Astrophysics | volume=505 | issue=3 | pages=1311–17 | date=2009 | arxiv=0908.1753 | bibcode=2009A&A...505.1311D | doi=10.1051/0004-6361/200911702 | s2cid=9686080 }}</ref> [[Astronomy:HD 120084|HD 120084]] is another evolved star, a yellow giant of spectral type G7III, around 2.4 times the mass of the Sun. It has a planet 4.5 times the mass of Jupiter, with one of the most eccentric planetary orbits (e = 0.66), discovered by precisely measuring the radial velocity of the star in 2013.<ref>{{cite journal | arxiv=1304.4328  |title=Planetary Companions to Three Evolved Intermediate-Mass Stars: HD 2952, HD 120084, and omega Serpentis| url=https://archive.org/details/arxiv-1304.4328  |author= Sato, Bun'ei|author2= Omiya, Masashi|author3=  Harakawa, Hiroki|author4=  Liu, Yu-Juan|author5=  Izumiura, Hideyuki|author6=  Kambe, Eiji|author7=  Takeda, Yoichi|author8=  Yoshida, Michitoshi|author9=  Itoh, Yoichi|author10=  Ando, Hiroyasu|author11=  Kokubo, Eiichiro|author12=  Ida, Shigeru | journal= [[Organization:Publications of the Astronomical Society of Japan|Publications of the Astronomical Society of Japan]] |pages = [https://archive.org/details/arxiv-1304.4328/page/n0 1]–15 |date=2013|volume=65|issue=4|bibcode = 2013PASJ...65...85S |doi = 10.1093/pasj/65.4.85 |s2cid=119248666}}</ref> [[Astronomy:HD 150706|HD 150706]] is a sunlike star of spectral type G0V some 89 light-years distant from the Solar System. It was thought to have a planet as massive as Jupiter at a distance of 0.6 AU, but this was discounted in 2007.<ref>{{cite journal|author=Wright, J.T.|author2=Marcy, G.W.|author3=Fischer, D. A.|author4=Butler, R. P.|author5=Vogt, S. S.|author6=Tinney, C. G.|author7=Jones, H. R. A.|author8=Carter, B. D.|author9=Johnson, J. A.|author10=McCarthy, C.|author11=Apps, K.|date=2007|title=Four New Exoplanets and Hints of Additional Substellar Companions to Exoplanet Host Stars|journal=The Astrophysical Journal|volume=657|issue=1|pages=533–45|doi=10.1086/510553 |bibcode=2007ApJ...657..533W|arxiv = astro-ph/0611658 |s2cid=35682784}}</ref> A further study published in 2012 showed that it has a companion around 2.7 times as massive as Jupiter that takes around 16 years to complete an orbit and is 6.8 AU distant from its star.<ref name="Boisse2012">{{citation |doi=10.1051/0004-6361/201118419 |arxiv=1205.5835 |url=http://www.aanda.org/articles/aa/full_html/2012/09/aa18419-11/aa18419-11.html |title=The SOPHIE search for northern extrasolar planets V. Follow-up of ELODIE candidates: Jupiter-analogs around Sun-like stars |year=2012 |last1=Boisse |first1=Isabelle |last2=Pepe |first2=Francesco |last3=Perrier |first3=Christian |last4=Queloz |first4=Didier |last5=Bonfils |first5=Xavier |last6=Bouchy |first6=François |last7=Santos |first7=Nuno C. |last8=Arnold |first8=Luc |last9=Beuzit |first9=Jean-Luc |last10=Dìaz |first10=Rodrigo F. |last11=Delfosse |first11=Xavier |last12=Eggenberger |first12=Anne |last13=Ehrenreich |first13=David |last14=Forveille |first14=Thierry |last15=Hébrard |first15=Guillaume |last16=Lagrange |first16=Anne-Marie |last17=Lovis |first17=Christophe |last18=Mayor |first18=Michel |last19=Moutou |first19=Claire |last20=Naef |first20=Dominique |last21=Santerne |first21=Alexandre |last22=Ségransan |first22=Damien |last23=Sivan |first23=Jean-Pierre |last24=Udry |first24=Stéphane |journal=Astronomy and Astrophysics |volume=545 |pages=A55 |bibcode=2012A&A...545A..55B |s2cid=119109836 }}</ref>

=== Deep-sky objects ===
[[File:NGC 6217 hs-2009-25-bc-full.jpg|thumb|right|NGC 6217]]
Ursa Minor is rather devoid of deep-sky objects. The [[Astronomy:Ursa Minor Dwarf|Ursa Minor Dwarf]], a [[Astronomy:Dwarf spheroidal galaxy|dwarf spheroidal galaxy]], was discovered by [[Biography:Albert George Wilson|Albert George Wilson]] of the [[Astronomy:Lowell Observatory|Lowell Observatory]] in the Palomar Sky Survey in 1955.<ref>{{cite book|last=Bergh|first=Sidney |title=The Galaxies of the Local Group|publisher=Cambridge University Press|location=Cambridge, UK|date=2000|page=257|isbn=978-1-139-42965-8|url=https://books.google.com/books?id=H0JMeoqFqEcC&q=variable+stars+ursa+minor&pg=PA257}}</ref> Its centre is around {{val|225,000}} light-years distant from Earth.<ref>{{cite journal|author=Grebel, Eva K.|author2=Gallagher, John S., III|author3=Harbeck, Daniel|title=The Progenitors of Dwarf Spheroidal Galaxies|journal=The Astronomical Journal|date=2003|volume=125|issue=4|pages=1926–39|doi=10.1086/368363 | bibcode=2003AJ....125.1926G|arxiv = astro-ph/0301025 |s2cid=18496644}}</ref> In 1999, Kenneth Mighell and Christopher Burke used the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] to confirm that the galaxy had had a single burst of [[Astronomy:Star formation|star formation]] that took place around 14&nbsp;billion years ago and lasted around 2&nbsp;billion years,<ref name="Bergh2000">{{Cite journal | last1 = van den Bergh | first1 = Sidney |  title = Updated Information on the Local Group  | date = April 2000 | journal = The Publications of the Astronomical Society of the Pacific | volume = 112 | issue = #770 | bibcode = 2000PASP..112..529V | pages = 529–36 | doi = 10.1086/316548 |arxiv = astro-ph/0001040 | s2cid = 1805423 }}</ref> and that the galaxy was probably as old as the Milky Way itself.<ref>{{cite journal|author=Mighell, Kenneth J.|author2=Burke, Christopher J.|date=1999|title=WFPC2 Observations of the Ursa Minor Dwarf Spheroidal Galaxy|journal=The Astronomical Journal|volume=118|issue=366|pages=366–380|doi=10.1086/300923|arxiv = astro-ph/9903065 |bibcode = 1999AJ....118..366M |s2cid=119085245}}</ref>

[[Astronomy:NGC 3172|NGC 3172]] (also known as Polarissima Borealis) is a faint, magnitude-14.9 [[Astronomy:Galaxy|galaxy]] that happens to be the closest [[Astronomy:NGC object|NGC object]] to the north celestial pole.<ref name="SIMBAD NGC3172">{{Cite web|title=NGC 3172|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%40331138&Name=NGC++3172&submit=display+all+measurements#lab_meas%20SIMBAD:%20NGC%203054%20--%20Galaxy|website=sim-id|access-date=2020-05-29}}</ref> It was discovered by [[Biography:John Herschel|John Herschel]] in 1831.<ref>{{Cite web|title=New General Catalog Objects: NGC 3150 - 3199|url=https://cseligman.com/text/atlas/ngc31a.htm#3172|website=cseligman.com|access-date=2020-05-30}}</ref>

[[Astronomy:NGC 6217|NGC 6217]] is a [[Astronomy:Barred spiral galaxy|barred spiral galaxy]] located some 67 million light-years away,<ref name="Gusev2012">{{Cite journal  | last1   = Gusev | first1  = A. S. | last2   = Pilyugin | first2  = L. S. | last3   = Sakhibov | first3  = F. | last4   = Dodonov | first4  = S. N. | last5   = Ezhkova | first5  = O. V. | last6   = Khramtsova | first6  = M. S. | last7   = Garzónhuhed | first7  = F. | title   = Oxygen and Nitrogen Abundances of H II regions in Six Spiral Galaxies | journal = [[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] | volume  = 424 | issue   = #3 | pages   = 1930–40 |date=2012 | arxiv   = 1205.3910 | doi     = 10.1111/j.1365-2966.2012.21322.x | bibcode = 2012MNRAS.424.1930G| s2cid = 118437910 }}</ref> which can be located with a {{Convert|4|in|cm|abbr=on|order=flip}} or larger [[Astronomy:Telescope|telescope]] as an 11th-magnitude object about 2.5° east-northeast of Zeta Ursae Minoris.<ref name="OMeara2007">{{Cite book | first1  = Stephen James | last1= O'Meara | title= Steve O'Meara's Herschel 400 Observing Guide | publisher = Cambridge University Press |location=Cambridge, UK| page= 227 | date = 2007 | isbn= 978-0-521-85893-9 | url = https://books.google.com/books?id=Nyh9fAC_tpIC&pg=PA227}}</ref> It has been characterized as a [[Astronomy:Starburst galaxy|starburst galaxy]], which means it is undergoing a high rate of star formation compared with a typical galaxy.<ref>{{cite journal|last= Calzetti|first=Daniela|date=1997|title=Reddening and Star Formation in Starburst Galaxies|journal=Astronomical Journal|volume=113|pages=162–84|doi=10.1086/118242 | bibcode=1997AJ....113..162C|arxiv = astro-ph/9610184 |s2cid=16526015}}</ref>

[[Astronomy:NGC 6251|NGC 6251]] is an active supergiant elliptical [[Astronomy:Radio galaxy|radio galaxy]] more than 340 million light-years away from Earth. It has a Seyfert 2 [[Active galactic nucleus|active galactic nucleus]], and is one of the most extreme examples of a [[Astronomy:Seyfert galaxy|Seyfert galaxy]]. This galaxy may be associated with gamma-ray source 3EG J1621+8203, which has high-energy gamma-ray emission.<ref name=SIMBADngc6251>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=QSO+B1637%2B826 |title = NGC 6251 – Seyfert 2 Galaxy  |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 21 July 2015}}</ref><!-- cites previous 3 sentences --> It is also noted for its one-sided [[Astronomy:Astrophysical jet|radio jet]]—one of the brightest known—discovered in 1977.<ref>{{cite journal|author1=Perley, R. A. |author2=Bridle, A. H. |author3=Willis, A. G. |date=1984|title=High-resolution VLA Observations of the Radio Jet in NGC 6251|journal=Astrophysical Journal Supplement Series|volume=54|pages=291–334|doi=10.1086/190931 | bibcode=1984ApJS...54..291P}}</ref>

=== Meteor showers ===
The [[Astronomy:Ursids|Ursids]], a prominent meteor shower that occurs in Ursa Minor, peaks between December 18 and 25. Its parent body is the comet 8P/Tuttle.<ref>{{cite journal |last = Jenniskens |first = Peter |date = September 2012 |title = Mapping Meteoroid Orbits: New Meteor Showers Discovered | journal = Sky & Telescope |page = 24}}</ref>

== See also ==
* [[Astronomy:Polaris Flare|Polaris Flare]]
* Ursa Minor Beta, fictional planet in ''The Hitchhiker's Guide to the Galaxy''
* Ursa Minor (Chinese astronomy)

== Notes ==
{{Notelist}}

== References ==
{{Reflist|30em}}

== External links ==
{{Commons}}
* [http://www.allthesky.com/constellations/ursaminor/ The Deep Photographic Guide to the Constellations: Ursa Minor]
* [http://astrojan.nhely.hu/ursami.htm The clickable Ursa Minor]
* [https://iconographic.warburg.sas.ac.uk/category/vpc-taxonomy-017039 Warburg Institute Iconographic Database (ca 160 medieval and early modern images of Ursa Minor)]

{{Sky|15|00|00|+|75|00|00|10}}

{{Stars of Ursa Minor}}
{{Constellations}}

[[Category:Constellations]]
[[Category:Northern constellations]]
[[Category:Constellations listed by Ptolemy]]

{{Sourceattribution|Ursa Minor}}