Editing Altair (section)

{{Short description|Brightest star in the constellation Aquila}}
{{About|a star in the constellation Aquila}}
{{good article}}
{{Starbox begin}}
{{Starbox image
 | image=
   {{Location mark
     | image=Aquila constellation map.svg
     | float=center | width=260 | position=right
     | mark=Red circle.svg | mark_width=12 | mark_link=Altair (star)
     | x=440 | y=339
   }}
 | caption=Location of Altair (circled)
}}
{{Starbox observe
 | epoch = [[J2000.0]]97
 | equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]])
 | constell = [[Aquila (constellation)|Aquila]]
 | pronounce = {{IPAc-en|'|æ|l|t|ɛər|audio=LL-Q1860 (eng)-Naomi Persephone Amethyst (NaomiAmethyst)-Altair.wav}}, {{IPAc-en|'|æ|l|t|aɪər|audio=LL-Q1860 (eng)-Naomi Persephone Amethyst (NaomiAmethyst)-Altair (alt).wav}}<ref>{{cite web|url=http://www.oxforddictionaries.com/definition/american_english/altair|archive-url=https://web.archive.org/web/20140512142137/http://www.oxforddictionaries.com/definition/american_english/Altair|url-status=dead|archive-date=May 12, 2014|title=Altair: definition of Altair in Oxford dictionary (American English)}}</ref><ref name=Kunitzsch>{{cite book |last1=Kunitzsch |first1=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>
 | ra = {{RA|19|50|46.99855}}<ref name=aaa474_2_653/>
 | dec = {{DEC|+08|52|05.9563}}<ref name=aaa474_2_653/>
 | appmag_v = 0.76<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|date=2002}}</ref>
}}
{{Starbox character
 | type=[[Main sequence]]
 | class = A7Vn<ref name=gray_et_al_2003/>
 | u-b = +0.09<ref name=ducati/>
 | b-v = +0.22<ref name=ducati/>
 | v-r = +0.14<ref name=ducati/>
 | r-i = +0.13<ref name=ducati/>
 | variable = [[Delta Scuti variable|Delta Scuti]]<ref name="Buzasi et al 2005"/>
}}
{{Starbox astrometry
 | radial_v = {{val|−26.1|0.9}}<ref name=sb0/>
 | prop_mo_ra = +536.23<ref name=aaa474_2_653/>
 | prop_mo_dec = +385.29<ref name=aaa474_2_653/>
 | parallax = 194.95
 | p_error = 0.57
 | parallax_footnote = <ref name=aaa474_2_653/>
 | absmag_v= 2.22<ref name="Buzasi et al 2005"/>
}}
{{Starbox detail|
 | mass = {{val|1.86|0.03}}<ref name=bouchaud2020/>
 | radius = 2.007 (equatorial)<br>1.565 (polar)<ref name=bouchaud2020/>
 | gravity = 4.29<ref name=aass85_3_1015/>
 | rotation = 7.77 hours<ref name=peterson06/>
 | luminosity = 10.6<ref name=peterson06/>
 | temperature = 6,780 (equatorial)<br>8,620 (polar)<ref name=bouchaud2020/>
 | metal_fe = −0.2<ref name=monnier07/>
 | rotational_velocity = 242<ref name=bouchaud2020/>
 | age_myr = {{val|88|10}}<ref name=Rieutord2024/>
}}
{{Starbox catalog
| names = {{odlist | name=Atair | B=α&nbsp;Aquilae, α&nbsp;Aql, Alpha&nbsp;Aquilae, Alpha&nbsp;Aql | F=53&nbsp;Aquilae, 53&nbsp;Aql | BD=+08°4236 | FK5=745 | GCTP=4665.00 | GJ=768 | HD=187642 | HIP=97649 | HR=7557 | LFT=1499 | LHS=3490 | LTT=15795 | NLTT=48314 | SAO=125122 | WDS=19508+0852A }}<ref name=sb0/><ref name=bsc1/><ref name=wds/> | LA001
}}
{{Starbox reference
 | Simbad = alf+aql
}}
{{Starbox end
}}

'''Altair''' is the brightest [[star]] in the [[constellation]] of [[Aquila (constellation)|Aquila]] and the [[list of brightest stars|twelfth-brightest star]] in the [[night sky]]. It has the [[Bayer designation]] Alpha&nbsp;Aquilae, which is [[Latinisation of names|Latinised]] from '''α&nbsp;Aquilae''' and abbreviated '''Alpha&nbsp;Aql''' or '''α&nbsp;Aql'''. Altair is an [[A-type main-sequence star|A-type]] [[main-sequence star]] with an [[apparent visual magnitude]] of 0.77 and is one of the vertices of the [[Summer Triangle]] [[Asterism (astronomy)|asterism]]; the other two vertices are marked by [[Deneb]] and [[Vega]].<ref name=sb0/><ref name=darlingaltair/><ref name="darlingsummer">{{Cite web |last=Darling |first=David |title=Summer Triangle |url=http://www.daviddarling.info/encyclopedia/S/Summer_Triangle.html |access-date=2008-11-26 |website=www.daviddarling.info}}</ref> It is located at a distance of {{convert|16.7|ly|pc|abbr=off|lk=on}} from the [[Sun]].<ref name="schaaf2008">{{Cite book |last=Hoboken |first=Fred Schaaf |title=The brightest stars : discovering the universe through the sky's most brilliant stars |publisher=John Wiley & Sons, Inc. |year=2008 |isbn=978-0-471-70410-2 |location=New Jersey |pages= |oclc=440257051}}</ref>{{Citation page|page=194}} Altair is currently in the [[G-cloud]]—a nearby [[interstellar cloud]] formed from an accumulation of gas and dust.<ref>{{Cite web|url=http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/neighborhood.html|title=Our Local Galactic Neighborhood|publisher=[[NASA]]|archive-url=https://web.archive.org/web/20131121061128/http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/neighborhood.html|archive-date=2013-11-21|url-status=dead}}</ref><ref>{{Cite news|url=http://www.centauri-dreams.org/?p=14203|title=Into the Interstellar Void|last=Gilster|first=Paul|date=2010-09-01|work=Centauri Dreams|access-date=2017-03-26|language=en-US}}</ref> 

Altair rotates rapidly, with a velocity at the [[equator]] of approximately 286&nbsp;km/s.<ref group=nb>From values of ''v'' sin ''i'' and ''i'' in the second column of Table 1, Monnier et al. 2007.</ref><ref name=monnier07/> This is a significant fraction of the star's estimated breakup speed of 400&nbsp;km/s.<ref name=robrade2009/> A study with the [[Palomar Testbed Interferometer]] revealed that Altair is not spherical, but is flattened at the poles due to its high rate of rotation.<ref name="pti2001">{{Cite journal|last1=Belle|first1=Gerard T. van|last2=Ciardi|first2=David R.|last3=Thompson|first3=Robert R.|last4=Akeson|first4=Rachel L.|last5=Lada|first5=Elizabeth A.|year=2001|title=Altair's Oblateness and Rotation Velocity from Long-Baseline Interferometry|url=http://stacks.iop.org/0004-637X/559/i=2/a=1155|journal=The Astrophysical Journal|language=en|volume=559|issue=2|pages=1155–1164|bibcode=2001ApJ...559.1155V|doi=10.1086/322340|s2cid=13969695 |issn=0004-637X}}</ref> Other [[interferometric]] studies with multiple telescopes, operating in the [[infrared]], have imaged and confirmed this phenomenon.<ref name="monnier07">{{Cite journal|last2=Zhao|first2=M|last3=Pedretti|first3=E|last4=Thureau|first4=N|last5=Ireland|first5=M|last6=Muirhead|first6=P|last7=Berger|first7=J. P.|last8=Millan-Gabet|first8=R|last9=Van Belle|first9=G|year=2007|title=Imaging the surface of Altair|journal=Science|volume=317|issue=5836|pages=342–345|bibcode=2007Sci...317..342M|doi=10.1126/science.1143205|pmid=17540860|last1=Monnier|first1=J. D.|last10=Ten Brummelaar|first10=T|last11=McAlister|first11=H|last12=Ridgway|first12=S|last13=Turner|first13=N|last14=Sturmann|first14=L|last15=Sturmann|first15=J|last16=Berger|first16=D|arxiv = 0706.0867 |s2cid=4615273}}  See second column of Table 1 for stellar parameters.</ref>