| 词条 | U Orionis |
| 释义 |
|name =U Orionis }}{{Starbox image | image={{Location mark |image=Gemini constellation map.svg|alt=|float=center|width=300 |label=|position=right |mark=Red circle.svg|mark_width=8|mark_link=U Ori |x=916|y=420 }} |caption=Location of U Orionis (circled) }}{{Starbox observe | epoch = J2000.0 | constell = Orion | ra={{RA|05|55|49.16994}}[1] | dec={{DEC|+20|10|30.6872}}[1] | appmag_v = 4.8 - 13.0 }}{{Starbox character | class = M8 III | r-i = | v-r = | b-v = +2.07[2] | u-b = | variable = Mira }}{{Starbox astrometry | parallax = 2.29 | p_error = 1.21 | parallax_footnote = [1] | dist_ly = 997.56 | dist_pc = 306 ± 61[3] }}{{Starbox detail | mass = | radius = 370 ± 96[4] | luminosity = 7,000[5] | temperature = ≈2,750[5] }}{{Starbox catalog | names = {{odlist|V=U Ori|HIP=28041|HD=39816|HR=2063|BD=+20° 1171a|SAO=77730}}[6] }}{{Starbox reference | Simbad = U+Ori }}{{Starbox end}} U Orionis (abbreviated U Ori) is a Mira-type variable star in the constellation Orion. It is a classical long period variable star that has been well observed from the United Kingdom for over 120 years. DiscoveryIt was discovered on 1885 December 13 by J.E. Gore and initially it was thought to be a nova in the early stages of decline (Gore's Nova and NOVA Ori 1885 as still listed in SIMBAD), but a spectrum taken at Harvard showed features similar to that of Mira. Thus U Orionis became the first long period variable to be identified by a photograph of its spectrum.[7] LocationU Orionis lies less than half a degree east of the small-amplitude variable star χ1 Orionis and less than an arc-minute from the much fainter eclipsing variable UW Orionis. χ1 Orionis is slightly brighter than U Orionis at its brightest maximum, while UW Orionis is more than a thousand times fainter, similar to U Orionis at minimum. Stellar parametersThe star has a low effective temperature (roughly 2700 K) but a large and bloated radius of 370 solar radii[4] and a high luminosity, 7,000 times higher than the Sun.[5] If the Sun were replaced with U Orionis, its radius would extend beyond Mars's orbital zone (about 1.7 astronomical units), and, to be habitable with water at liquid state and a comfortable temperature, a planet would have to be located within 85 AU, within the Kuiper belt's orbital zone.{{citation needed|date=August 2016}} Possible planetary systemAccording to Rudnitskij,[8] a 12- to 15-year "super-periodicity" has been observed. The author infers such periodicity could coincide with the revolution period of an invisible companion, probably planetary. So far no clear hint of planetary objects has been detected. References1. ^1 2 {{cite journal|title=Validation of the new Hipparcos reduction|url=http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL|author=van Leeuwen, F.|display-authors=etal|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|date=2007|arxiv=0708.1752|bibcode=2007A&A...474..653V|doi=10.1051/0004-6361:20078357}} {{Stars of Orion}}2. ^{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1|date=1986|bibcode= 1986EgUBV........0M}} 3. ^{{cite journal | author=Mondal| title=Evidence of asymmetry in Mira variable U Ori| journal=Bulletin of the Astronomical Society of India | volume=33| issue=2| pages=97–102 | date=2005 | bibcode=2005BASI...33...97M }} 4. ^1 {{cite journal | author=Van Belle| display-authors=etal| title=Angular Size Measurements of 18 Mira Variable Stars at 2.2 microns| journal=Astronomical Journal | volume=112| pages=2147 | date=1996 | bibcode=1996AJ....112.2147V | doi=10.1086/118170}} 5. ^1 2 {{cite journal | author=Mondal | author2=Chandrasekhar | last-author-amp=yes| title=Evidence of asymmetry in Mira variable U Ori| journal=Monthly Notices of the Royal Astronomical Society | volume=348| issue=4| pages=1332–1336 | date=2004 | doi=10.1111/j.1365-2966.2004.07454.x | bibcode=2004MNRAS.348.1332M}} 6. ^{{cite simbad|title=V* U Ori|access-date=25 January 2018}} 7. ^{{cite journal | author=Monck | title=Mr Gore's Nova Orionis | journal=The Observatory | volume=10| pages=69–71 | date=1887 | bibcode=1887Obs....10...69M}} 8. ^{{cite journal | author=Rudnitskij | title=Molecular Masers in Variable Stars | journal=Publications of the Astronomical Society of Australia | volume=19| issue=4| pages=499–504 | date=2002| bibcode=2002PASA...19..499R | doi=10.1071/AS02018 }} 8 : Orion (constellation)|Mira variables|Objects with variable star designations|M-type giants|Henry Draper Catalogue objects|HR objects|Hipparcos objects|Durchmusterung objects |
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