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{{redirect|알나이르|센타우루스자리의 항성|센타우루스자리 제타}}
{{항성 정보
| 이름 = 두루미자리 알파<br>(알나이르)
| 로마자이름 = Alpha Gruis (Alnair)
| 그림 =
<div style="position: relative">[[File:Grus IAU.svg|250px|alt=Diagram showing star positions and boundaries of the Grus constellation and its surroundings]]
<div style="position: absolute; left: 54.6%; top: 47.5%;">[[File:Cercle rouge 100%.svg|12px]]</div>
</div>
| 그림설명 = Location of α Gruis (circled)
}}
{{Starbox observe
| epoch = J2000
| ra = {{RA|22|08|13.98473}}<ref name=aaa474_2_653/>
| dec = {{DEC|–46|57|39.5078}}<ref name=aaa474_2_653/>
| appmag_v = +1.74<ref name="bsc1"/>
| constell = [[Grus (constellation)|Grus]]
}}
{{Starbox character
| class = B6 V<ref name=aj132_1_161/>
| b-v = –0.13<ref name="bsc1"/>
| u-b = –0.47<ref name="bsc1"/>
| variable =
}}
{{Starbox astrometry
| radial_v = +11.8<ref name=wilson1953/>
| prop_mo_ra = +126.69<ref name=aaa474_2_653/>
| prop_mo_dec = −147.47<ref name=aaa474_2_653/>
| parallax = 32.29
| p_error = 0.21
| parallax_footnote = <ref name=aaa474_2_653/>
| absmag_v = −0.72<ref name=Anderson2012/>
}}
{{Starbox detail
| mass = 4.0<ref name=aass85_3_1015/>
| radius = 3.4<ref name=aaa431_773/>
| luminosity = 520<ref name=aj143_6/>
| gravity = {{nowrap|3.76 ± 0.11}}<ref name=apj525_2_1011/>
| temperature = 13,920<ref name=aaa501_1_297/>
| metal_fe = {{nowrap|–0.13 ± 0.02}}<ref name=aaa404_689/>
| rotational_velocity = 215<ref name=aaass43_427/>
| age_myr = 100<ref name=apj653_1_675/>
}}
{{Starbox catalog
| names = Al Na'ir, α Gru, [[Cordoba Durchmusterung|CD]]−47°14063, [[Fifth Fundamental Catalogue|FK5]] 829, [[General Catalogue of Trigonometric Parallaxes|GCTP]] 5339.00, [[Gliese Catalogue of Nearby Stars|Gl]] 848.2, [[Henry Draper catalogue|HD]] 209952, [[Hipparcos catalogue|HIP]] 109268, [[Harvard Revised catalogue|HR]] 8425, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 230992<ref name=SIMBAD/>
}}
{{Starbox reference
|Simbad=alf+Gru
}}
{{Starbox end}}
'''Alpha Gruis''', [[Latinisation of names|Latinized]] from '''α Gruis''', officially named '''Alnair''' {{IPAc-en|æ|l|'|n|ɛər}},<ref name=Kunitzsch>{{cite book
|last=Kunitzsch |first=Paul
|last2=Smart |first2=Tim
|date = 2006 |edition = 2nd rev.
|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
|publisher = Sky Pub |location = Cambridge, Massachusetts
|isbn = 978-1-931559-44-7
}}</ref> is a single [[star]] in the southern [[constellation]] of [[Grus (constellation)|Grus]]. At [[apparent magnitude|magnitude]] 1.7 it is the brightest [[star]] in Grus and [[List of brightest stars|one of the brightest stars]] in the sky. It is a [[B-type main-sequence star]] {{val|31|ul=pc}} away.
==Nomenclature==
''α Gruis'' ([[Latinisation of names|Latinised]] to ''Alpha Gruis'') is the star's [[Bayer designation]]. (Its first depiction in a [[Celestial cartography|celestial atlas]] was in [[Johann Bayer]]'s ''[[Uranometria]]'' of 1603.<ref name=scalzi2008/>)
It bore the traditional name ''Alnair'' or ''Al Nair'' (sometimes ''Al Na'ir'' in [[List_of_selected_stars_for_navigation|lists of stars used by navigators]]<ref name="Bowditch"/>), from the [[Arabic]] ''al-nayyir'' "the bright one", itself derived from its Arabic name, ''al-nayyir min dhanab al-ḥūt (al-janūbiyy)'', "the bright one from the [[Piscis Austrinus|(southern) fish's]] tail" (see [[Aldhanab]]).<ref name=kunitzsch_smart2006/> Confusingly, ''Alnair'' was also given as the proper name for [[Zeta Centauri]] in an [[Bureau des Longitudes#Publications|astronomical ephemerides]] in the middle of the 20th century.<ref name=kunitzsch1959/> In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN approved the name ''Alnair'' for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN"/>
Along with [[Beta Gruis]], [[Delta Gruis]], [[Theta Gruis]], [[Iota Gruis]], and [[Lambda Gruis]], Alpha Gruis belonged to [[Piscis Austrinus]] in traditional [[Arabian astronomy|Arabic astronomy]].<ref name=allen1963/>
In [[Chinese language|Chinese]], {{lang|zh|鶴}} ({{lang|zh-Latn|Hè}}), meaning ''[[Chinese constellations#The Southern Asterisms (近南極星區)|Crane]]'', refers to an [[Asterism (astronomy)|asterism]] consisting of Alpha Gruis, [[Beta Gruis]], [[Delta2 Gruis|Delta<sup>2</sup> Gruis]], [[Epsilon Gruis]], [[Zeta Gruis]], [[Eta Gruis]], [[Iota Gruis]], [[Theta Gruis]], [[Mu1 Gruis|Mu<sup>1</sup> Gruis]] and [[Delta Tucanae]].<ref name=zh/> Consequently, Alpha Gruis itself is known as {{lang|zh|鶴一}} ({{lang|zh-Latn|Hè yī}}, {{lang-en|First Star of the Crane}}).<ref name=lcsd/> The Chinese name gave rise to another English name, ''Ke''.<ref name=allen/>
==Properties==
Alpha Gruis has a [[stellar classification]] of B6 V,<ref name=aj132_1_161/> although some sources give it a classification of B7 IV.<ref name=mnras389_2_869/> The first classification indicates that this is a [[B-type star]] on the [[main sequence]] of stars that are generating energy through the [[thermonuclear fusion]] of hydrogen at the core. However, a luminosity class of 'IV' would suggest that this is a [[subgiant star]]; meaning the supply of hydrogen at its core is becoming exhausted and the star has started the process of [[stellar evolution|evolving]] away from the main sequence. It has no known companions.<ref name=mnras389_2_869/>
The measured [[angular diameter]] of this star, after correcting for limb darkening, is {{nowrap|1.02 ± 0.07 [[milliarcseconds|mas]]}}.<ref name=aaa431_773/> At a [[parallax]]-measured distance of {{Convert|101|ly|pc|abbr=off|lk=on}} from [[Earth]], this yields a physical size of 3.4 times the [[Solar radius|radius of the Sun]].<ref name=lang2006/> It is rotating rapidly, with a [[stellar rotation|projected rotational velocity]] of about 215 km/s providing a lower bound for the rate of [[azimuth]]al rotation along the equator.<ref name=aaass43_427/> This star has around four times the [[Solar mass|Sun's mass]] and is radiating roughly 520 times the [[Solar luminosity|luminosity of the Sun]].<ref name=aj143_6/>
The [[effective temperature]] of Alpha Gruis's outer envelope is 13,920 K,<ref name=aaa501_1_297/> giving it the blue-white hue characteristic of B-type stars.<ref name=csiro/> The abundance of elements other than [[hydrogen]] and [[helium]], what astronomers term the [[metallicity]], is about 74% of the abundance in the [[Sun]].<ref name=aaa404_689/>
Based on the estimated age and motion, it may be a member of the [[AB Doradus moving group]] that share a common motion through space. This group has an age of about 70 million years,<ref name=apj732_2_61/> which is consistent with α Gruis's 100-million-year<ref name=apj653_1_675/> estimated age (allowing for a margin of error). The [[space velocity (astronomy)|space velocity]] components of this star in the [[Galactic coordinate system]] are [''U'', ''V'', ''W''] = {{nowrap|[–7.0 ± 1.1}}, {{nowrap|–25.6 ± 0.7}}, {{nowrap|–15.5 ± 1.4] km/s}}.<ref name=apj732_2_61/>
== References ==
{{Reflist|30em|refs=
<ref name=aaa474_2_653>{{cite journal | title=Validation of the new Hipparcos reduction | last=van Leeuwen | first=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 |date=November 2007 | pages=653–664 | doi=10.1051/0004-6361:20078357 | bibcode=2007A&A...474..653V |arxiv = 0708.1752 }}</ref>
<ref name=Anderson2012>{{cite journal
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 }}</ref>
<ref name=aj132_1_161>{{cite journal | display-authors=1 | last1=Gray | first1=R. O. | last2=Corbally | first2=C. J. | last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T. | last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E. | last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R. | title=Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample | journal=[[The Astronomical Journal]] | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G | arxiv=astro-ph/0603770 }}</ref>
<ref name=wilson1953>{{cite journal | last=Wilson | first=Ralph Elmer | date=1953 | title=General catalogue of stellar radial velocities | journal=Washington | pages=0 | bibcode=1953GCRV..C......0W }}</ref>
<ref name="bsc1">{{cite web|url=http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/50/catalog&recno=8425 |title= HR 8425, database entry |work= The Bright Star Catalogue |edition=5th Revised (Preliminary) |author=Hoffleit, D. |author2=Warren, W. H. Jr.| publisher= [[Centre de Données astronomiques de Strasbourg|CDS]] |accessdate=5 September 2015}}</ref>
<ref name=SIMBAD>{{cite web | title=LTT 8869 -- High proper-motion Star | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alpha+Gruis | accessdate=2011-12-24 }}</ref>
<ref name=apj732_2_61>{{cite journal | display-authors=1 | last1=Zuckerman | first1=B. | last2=Rhee | first2=Joseph H. | last3=Song | first3=Inseok | last4=Bessell | first4=M. S. | title=The Tucana/Horologium, Columba, AB Doradus, and Argus Associations: New Members and Dusty Debris Disks | journal=The Astrophysical Journal | volume=732 | issue=2 | page=61 |date=May 2011 | doi=10.1088/0004-637X/732/2/61 | bibcode=2011ApJ...732...61Z |arxiv = 1104.0284 }}</ref>
<ref name=aaa501_1_297>{{cite journal | display-authors=1 | last1=Zorec | first1=J. | last2=Cidale | first2=L. | last3=Arias | first3=M. L. | last4=Frémat | first4=Y. | last5=Muratore | first5=M. F. | last6=Torres | first6=A. F. | last7=Martayan | first7=C. | title=Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff | journal=Astronomy and Astrophysics | volume=501 | issue=1 | pages=297–320 |date=July 2009 | doi=10.1051/0004-6361/200811147 | bibcode=2009A&A...501..297Z |arxiv = 0903.5134 }}</ref>
<ref name=mnras389_2_869>{{cite journal | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=389 | issue=2 | pages=869–879 |date=September 2008 | doi=10.1111/j.1365-2966.2008.13596.x | bibcode=2008MNRAS.389..869E |arxiv = 0806.2878 }}</ref>
<ref name=aaa404_689>{{cite journal | last1=Niemczura | first1=E. | title=Metallicities of the SPB stars from the IUE ultraviolet spectra | journal=Astronomy and Astrophysics | volume=404 | issue=2 | pages=689–700 |date=June 2003 | doi=10.1051/0004-6361:20030546 | bibcode=2003A&A...404..689N | doi-access=free }}. The fractional abundance relative to the Sun is given by:
:10<sup>−0.13</sup> = 0.74, or 74%.</ref>
<ref name=apj653_1_675>{{cite journal | display-authors=1 | last1=Su | first1=K. Y. L. | last2=Rieke | first2=G. H. | last3=Stansberry | first3=J. A. | last4=Bryden | first4=G. | last5=Stapelfeldt | first5=K. R. | last6=Trilling | first6=D. E. | last7=Muzerolle | first7=J. | last8=Beichman | first8=C. A. | last9=Moro-Martin | first9=A. | title=Debris Disk Evolution around A Stars | journal=The Astrophysical Journal | volume=653 | issue=1 | pages=675–689 |date=December 2006 | doi=10.1086/508649 | bibcode=2006ApJ...653..675S |arxiv = astro-ph/0608563 }}</ref>
<ref name=aaass43_427>{{cite journal | display-authors=1 | last1=Dachs | first1=J. | last2=Eichendorf | first2=W. | last3=Schleicher | first3=H. | last4=Schmidt-Kaler | first4=T. | last5=Stift | first5=M. | last6=Tug | first6=H. | title=Photoelectric scanner measurements of Balmer emission line profiles for southern Be stars. II - A survey for variations | journal=Astronomy and Astrophysics Supplement Series | volume=43 | pages=427–453 |date=March 1981 | bibcode=1981A&AS...43..427D }}</ref>
<ref name=apj525_2_1011>{{cite journal | last1=Fitzpatrick | first1=Edward L. | last2=Massa | first2=Derck | title=Determining the Physical Properties of the B Stars. I. Methodology and First Results | journal=The Astrophysical Journal | volume=525 | issue=2 | pages=1011–1023 |date=November 1999 | doi=10.1086/307944 | bibcode=1999ApJ...525.1011F |arxiv = astro-ph/9906257 }}</ref>
<ref name=aaa431_773>{{cite journal | last1=Richichi | first1=A. | last2=Percheron | first2=I. | last3=Khristoforova | first3=M. | title=CHARM2: An updated Catalog of High Angular Resolution Measurements | journal=Astronomy and Astrophysics | volume=431 | issue=2 | pages=773–777 |date=February 2005 | doi=10.1051/0004-6361:20042039 | bibcode=2005A&A...431..773R | doi-access=free }}</ref>
<ref name=lang2006>{{cite book | first1=Kenneth R. | last1=Lang | title=Astrophysical formulae | volume=1 | series=Astronomy and astrophysics library | edition=3rd | publisher=Birkhäuser | date=2006 | isbn=978-3-540-29692-8 | url=https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41 }}. The radius (R<sub>*</sub>) is given by:
:<math>\begin{align} 2\cdot R_*
& = \frac{(10^{-3}\cdot 31\cdot 1.02)\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
& \approx 6.8\cdot R_{\bigodot}
\end{align}</math></ref>
<ref name=kunitzsch_smart2006>{{cite book | last1=Kunitzsch | first1=P. | last2=Smart | first2=T. | date=2006 | title=A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations | edition=2nd | publisher=[[Sky Publishing Corporation|Sky Publishing]] | location=[[Cambridge, Massachusetts|Cambridge]], [[Massachusetts|MA]] | isbn=978-1-931559-44-7 | page=39 }}</ref>
<ref name=kunitzsch1959>{{cite book | last1=Kunitzsch | first1=P. | date=1959 | title=Arabische Sternnamen in Europa | publisher=[[Otto Harrassowitz]] | location=[[Wiesbaden]] | page=128 }}</ref>
<ref name=allen1963>{{cite book | last1=Allen | first1=Richard H. | author-link=Richard Hinckley Allen | date=1963 | title=Star Names: Their Lore and Meaning | edition=reprint | publisher=[[Dover Publications]] Inc. | location=[[New York City|New York]], [[New York (state)|NY]] | isbn=978-0-486-21079-7 | page=[https://archive.org/details/starnamestheirlo00alle/page/237 237] | title-link=Star Names: Their Lore and Meaning }}</ref>
<ref name=scalzi2008>{{cite book | first1=John | last1=Scalzi | title=Rough Guide to the Universe | publisher=Penguin | date=2008 | isbn=978-1-4053-8370-7 | page=306 | url=https://books.google.com/books?id=dTE00bLcbPMC&pg=PA306 }}</ref>
<ref name=csiro>{{cite web|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |url-status=dead |archiveurl=https://www.webcitation.org/6630AbtJZ?url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=March 10, 2012 }}</ref>
<ref name=aass85_3_1015>{{cite journal | last1=Malagnini | first1=M. L. | last2=Morossi | first2=C. | title=Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars | journal=Astronomy and Astrophysics Supplement Series | volume=85 | issue=3 | pages=1015–1019 |date=November 1990 | bibcode=1990A&AS...85.1015M }}</ref>
<ref name=aj143_6>{{cite journal
| title=The Sizes of the Nearest Young Stars
| last1=McCarthy | first1=K. | last2=White | first2=R. J.
| journal=The Astronomical Journal
| volume=143 | issue=6 | pages=134
| date=June 2012
| bibcode=2012AJ....143..134M | doi=10.1088/0004-6256/143/6/134
| arxiv=1201.6600 }}</ref>
<ref name="Bowditch">{{cite book
| first = Nathaniel
| last = Bowditch, LL.D.
| authorlink = Nathaniel Bowditch
| title = The American Practical Navigator: An Epitome of Navigation
| publisher = [[National Imagery and Mapping Agency]]
| chapter-url = http://www.1yachtua.com/nauticalcharts/downloads/Practical_navigator.pdf
| date = 2002
| origyear = 1802
| location= Bethesda, MD
| isbn = 978-0-939837-54-0
| chapter = 15: Navigational Astronomy
| page= 248
| ref=Bowditch2002
| accessdate=2016-09-20
}}</ref>
<ref name="WGSN">{{cite web
| url=https://www.iau.org/science/scientific_bodies/working_groups/280/
| title=IAU Working Group on Star Names (WGSN)
| publisher=International Astronomical Union
| accessdate=22 May 2016 }}</ref>
<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |accessdate=28 July 2016}}</ref>
<ref name=zh>{{cite book|language=zh|author=陳久金|title=中國星座神話|url=https://books.google.com/books?id=0Vex0rYzdu8C|year=2005|publisher=五南圖書出版股份有限公司|isbn=978-986-7332-25-7}}</ref>
<ref name=allen>{{cite web |url=http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Grus*.html |author=Richard Hinckley Allen |title=Star Names — Their Lore and Meaning: Grus |accessdate=2019-01-15}}</ref>
<ref name=lcsd>{{cite web|language=zh|url=http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |title=香港太空館 - 研究資源 - 亮星中英對照表 |archive-url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |archive-date=2008-10-25 |publisher=Hong Kong Space Museum |accessdate=2019-01-15}}</ref>
}}
==External links==
*{{citation | first1=James B. | last1=Kaler | title=AL NAIR (Alpha Gruis) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/alnair.html | accessdate=2011-12-26 }}
{{두루미자리}}
[[분류:두루미자리]]
[[분류:준거성]]
[[분류:바이어 천체]]
[[분류:B형 주계열성]]
[[분류:헨리 드레이퍼 목록 천체]]
[[분류:HR 천체]]
[[분류:글리제 천체]]
[[분류:히파르코스 천체]]
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