Altair

File:AquilaCC.jpg

α Aquilae (Latinised to Alpha Aquilae) is the star's Bayer designation. The traditional name Altair has been used since medieval times. It is an abbreviation of the Arabic phrase {{lang|ar|النسر الطائر}} Al-Nisr Al-Ṭa'ir, "{{lang|en|the flying eagle}}".{{Cite web|url=https://www.dictionary.com/browse/altair|title=the definition of altair|website=www.dictionary.com|language=en|access-date=2018-09-30}}

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}} to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf |archive-date=2022-10-09 |url-status=live | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}} included a table of the first two batches of names approved by the WGSN, which included Altair for this star. It is now so entered in the IAU Catalog of Star Names.{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}

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File:Altair-Sun comparison.png

Along with β Aquilae and γ Aquilae, Altair forms the well-known line of stars sometimes referred to as the Family of Aquila or Shaft of Aquila.{{Citation page|page=190}}

Altair is a type-A main-sequence star with about 1.8 times the mass of the Sun and 11 times its luminosity. It is thought to be a young star close to the zero age main sequence at about 100 million years old, although previous estimates gave an age closer to one billion years old. Altair rotates rapidly, with a rotational period of under eight hours; for comparison, the equator of the Sun makes a complete rotation in a little more than 25 days. Altair's rotation is similar to, and slightly faster than, those of Jupiter and Saturn. Like those two planets, its rapid rotation causes the star to be oblate; its equatorial diameter is over 20 percent greater than its polar diameter.

File:AlphaAqlLightCurve.png for Altair, adapted from Buzasi et al. (2005)]]

Satellite measurements made in 1999 with the Wide Field Infrared Explorer showed that the brightness of Altair fluctuates slightly, varying by just a few thousandths of a magnitude with several different periods less than 2 hours. As a result, it was identified in 2005 as a Delta Scuti variable star. Its light curve can be approximated by adding together a number of sine waves, with periods that range between 0.8 and 1.5 hours.{{Cite journal |last1=Buzasi |first1=D. L. |last2=Bruntt |first2=H. |last3=Bedding |first3=T. R. |last4=Retter |first4=A. |last5=Kjeldsen |first5=H. |last6=Preston |first6=H. L. |last7=Mandeville |first7=W. J. |last8=Suarez |first8=J. C. |last9=Catanzarite |first9=J. |date=February 2005 |title=Altair: The Brightest δ Scuti Star |journal=The Astrophysical Journal |language=en |volume=619 |issue=2 |pages=1072–1076 |arxiv=astro-ph/0405127 |bibcode=2005ApJ...619.1072B |doi=10.1086/426704 |s2cid=16524681 |issn=0004-637X}} It is a weak source of coronal X-ray emission, with the most active sources of emission being located near the star's equator. This activity may be due to convection cells forming at the cooler equator.

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Image:Altair_PR_image6_(white).jpg]]

The angular diameter of Altair was measured interferometrically by R. Hanbury Brown and his co-workers at Narrabri Observatory in the 1960s. They found a diameter of 3{{nbsp}}milliarcseconds.{{cite journal |bibcode=1967MNRAS.137..393H |title=The stellar interferometer at Narrabri Observatory-II. The angular diameters of 15 stars |last1=Hanbury Brown |first1=R. |last2=Davis |first2=J. |last3=Allen |first3=L. R. |last4=Rome |first4=J. M. |journal=Monthly Notices of the Royal Astronomical Society |year=1967 |volume=137 |issue=4 |page=393 |doi=10.1093/mnras/137.4.393 |doi-access=free }} Although Hanbury Brown et al. realized that Altair would be rotationally flattened, they had insufficient data to experimentally observe its oblateness. Later, using infrared interferometric measurements made by the Palomar Testbed Interferometer in 1999 and 2000, Altair was found to be flattened. This work was published by G. T. van Belle, David R. Ciardi and their co-authors in 2001.

Theory predicts that, owing to Altair's rapid rotation, its surface gravity and effective temperature should be lower at the equator, making the equator less luminous than the poles. This phenomenon, known as gravity darkening or the von Zeipel effect, was confirmed for Altair by measurements made by the Navy Precision Optical Interferometer in 2001, and analyzed by Ohishi et al. (2004) and Peterson et al. (2006).{{cite journal | doi = 10.1086/422422| title = Asymmetric Surface Brightness Distribution of Altair Observed with the Navy Prototype Optical Interferometer| year = 2004| last1 = Ohishi| first1 = Naoko| last2 = Nordgren| first2 = Tyler E.| last3 = Hutter| first3 = Donald J.| journal = The Astrophysical Journal| volume = 612| issue = 1| pages = 463–471| arxiv = astro-ph/0405301| bibcode = 2004ApJ...612..463O| s2cid = 15857535}} Also, A. Domiciano de Souza et al. (2005) verified gravity darkening using the measurements made by the Palomar and Navy interferometers, together with new measurements made by the VINCI instrument at the VLTI.{{cite journal | doi = 10.1051/0004-6361:20042476| title = Gravitational-darkening of Altair from interferometry| year = 2005| last1 = Domiciano de Souza| first1 = A. | last2 = Kervella| first2 = P.| last3 = Jankov| first3 = S.| last4 = Vakili| first4 = F.| last5 = Ohishi| first5 = N.| last6 = Nordgren| first6 = T. E.| last7 = Abe| first7 = L.| journal = Astronomy & Astrophysics| volume = 442| issue = 2| pages = 567–578| bibcode = 2005A&A...442..567D| doi-access = free}}

Altair is one of the few stars for which a resolved image has been obtained.{{cite press release |url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=109612 |title=Gazing up at the Man in the Star? |publisher=National Science Foundation |date=May 31, 2007 |access-date=2022-08-03 }} In 2006 and 2007, J. D. Monnier and his coworkers produced an image of Altair's surface from 2006 infrared observations made with the MIRC instrument on the CHARA array interferometer; this was the first time the surface of any main-sequence star, apart from the Sun, had been imaged. The false-color image was published in 2007. The equatorial radius of the star was estimated to be 2.03 solar radii, and the polar radius 1.63 solar radii—a 25% increase of the stellar radius from pole to equator. The polar axis is inclined by about 60° to the line of sight from the Earth.

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Image:Altair.jpg

The term Al Nesr Al Tair appeared in Al Achsasi al Mouakket's catalogue, which was translated into Latin as Vultur Volans.{{cite journal|last=Knobel|first= E. B.|title=Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket|journal=Monthly Notices of the Royal Astronomical Society|volume=55|issue= 8|pages=429–438|date=June 1895|bibcode=1895MNRAS..55..429K|doi=10.1093/mnras/55.8.429|doi-access=free}} This name was applied by the Arabs to the asterism of Altair, β Aquilae and γ Aquilae and probably goes back to the ancient Babylonians and Sumerians, who called Altair "the eagle star".{{Citation page|pages=17-18}} The spelling Atair has also been used.{{Cite book |last=Allen |first=Richard Hinckley |url=http://archive.org/details/bub_gb_5xQuAAAAIAAJ |title=Star-names and their meanings |publisher=New York, Leipzig [etc.] G.E. Stechert |others=unknown library |year=1899 |pages=59–60}} Medieval astrolabes of England and Western Europe depicted Altair and Vega as birds.{{Cite journal | last1 = Gingerich | first1 = O.| doi = 10.1111/j.1749-6632.1987.tb37197.x | title = Zoomorphic Astrolabes and the Introduction of Arabic Star Names into Europe | journal = Annals of the New York Academy of Sciences | volume = 500 | pages = 89–104 | year = 1987 | issue = 1|bibcode = 1987NYASA.500...89G | s2cid = 84102853}}

The Koori people of Victoria also knew Altair as Bunjil, the wedge-tailed eagle, and β and γ Aquilae are his two wives the black swans. The people of the Murray River knew the star as Totyerguil.Aboriginal mythology: an A-Z spanning the history of aboriginal mythology from the earliest legends to the present day, Mudrooroo, London: HarperCollins, 1994, {{ISBN|1-85538-306-3}}.{{Citation page|page=4}} The Murray River was formed when Totyerguil the hunter speared Otjout, a giant Murray cod, who, when wounded, churned a channel across southern Australia before entering the sky as the constellation Delphinus.{{Citation page|page=115}}

In Chinese astronomy, the asterism consisting of Altair, β Aquilae and γ Aquilae is known as Hé Gǔ ({{lang|zh|河鼓}}; lit. "river drum"). The Chinese name for Altair is thus Hé Gǔ èr ({{lang|zh|河鼓二}}; lit. "river drum two", meaning the "second star of the drum at the river").{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 26, 2008. However, Altair is better known by its other names: Qiān Niú Xīng ({{lang|zh-hans|牵牛星}} / {{lang|zh-hant|牽牛星}}) or Niú Láng Xīng ({{lang|zh|牛郎星}}), translated as the cowherd star.{{Cite book |last=Mayers |first=William Frederick |url=http://archive.org/details/chinesereadersm01mayegoog |title=The Chinese reader's manual: A handbook of biographical, historical ... |publisher=American Presbyterian Mission Press |others=Harvard University |year=1874 |pages=97–98, 161 |author-link=William Frederick Mayers}}p. 72, China, Japan, Korea Culture and Customs: Culture and Customs, Ju Brown and John Brown, 2006, {{ISBN|978-1-4196-4893-9}}. These names are an allusion to a love story, The Cowherd and the Weaver Girl, in which Niulang (represented by Altair) and his two children (represented by β Aquilae and γ Aquilae) are separated from respectively their wife and mother Zhinü (represented by Vega) by the Milky Way. They are only permitted to meet once a year, when magpies form a bridge to allow them to cross the Milky Way.pp. 105–107, Magic Lotus Lantern and Other Tales from the Han Chinese, Haiwang Yuan and Michael Ann Williams, Libraries Unlimited, 2006, {{ISBN|978-1-59158-294-6}}. In the Japanese version of this legend, celebrated in the Tanabata festival, Altair is known as Hikoboshi (彦星).{{cite web |title=Hikoboshi and Orihime (ひこぼし：彦星 and おりひめ：織姫) |url=https://xing.fmi.uni-jena.de/mediawiki/index.php/Hikoboshi_and_Orihime |website=All Skies Encyclopaedia |publisher=IAU Working Group on Star Names |access-date=26 May 2025}}

The people of Micronesia called Altair Mai-lapa, meaning "big/old breadfruit", while the Māori people called this star Poutu-te-rangi, meaning "pillar of heaven".{{Cite book |last1=Ross |first1=Malcolm |url=https://books.google.com/books?id=bJFfm59fVr4C |title=The Lexicon of Proto-Oceanic: The Culture and Environment of Ancestral Oceanic Society. The physical environment. Volume 2 |last2=Pawley |first2=Andrew |last3=Osmond |first3=Meredith |date=2007-03-01 |publisher=ANU E Press |isbn=978-1-921313-19-6 |page=175 |language=en}}

In Western astrology, the star was ill-omened, portending danger from reptiles.

This star is one of the asterisms used by Bugis sailors for navigation, called bintoéng timoro, meaning "eastern star".{{cite book|author1=Kelley, David H. |author2=Milone, Eugene F. |author3=Aveni, A.F. |title=Exploring Ancient Skies: A Survey of Ancient and Cultural Astronomy|publisher=Springer|location=New York, New York|year=2011|page=344|isbn=978-1-4419-7623-9|url=https://books.google.com/books?id=ILBuYcGASxcC&pg=PA307}}

A group of Japanese scientists sent a radio signal to Altair in 1983 with the hopes of contacting extraterrestrial life.{{cite news |url=https://www.asahi.com/ajw/articles/14985246 |title='Anybody there?' Astronomers waiting for a reply from Altair |date=August 20, 2023 |website= |access-date=2023-08-25 }}

NASA announced Altair as the name of the Lunar Surface Access Module (LSAM) on December 13, 2007.{{cite news |url=http://www.collectspace.com/news/news-121307a.html |title=NASA names next-gen lunar lander Altair |date=December 13, 2007 |website=.collectSPACE |access-date=2022-08-03 }} The Russian-made Beriev Be-200 Altair seaplane is also named after the star.{{cite press release |url=http://www.beriev.com/eng/Pr_rel_e/pr_58e.html |title=Results of the competition for the best personal names for the Be-103 and the Be-200 amphibious aircraft |publisher=Beriev Aircraft Company |date=February 12, 2003 |access-date=2022-08-03 |archive-date=2021-11-05 |archive-url=https://web.archive.org/web/20211105063444/http://www.beriev.com/eng/Pr_rel_e/pr_58e.html |url-status=dead }}

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The bright primary star has the multiple star designation WDS 19508+0852A and has several faint visual companion stars, WDS 19508+0852B, C, D, E, F and G. All are much more distant than Altair and not physically associated.{{cite DR2}}

{{Componentbox begin

|designation=WDS 19508+0852

|footnote=Entry 19508+0852,

[http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewframe4.html The Washington Double Star Catalog] {{Webarchive|url=https://web.archive.org/web/20090131051103/http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewframe4.html |date=2009-01-31 }},

United States Naval Observatory. Accessed online November 25, 2008.

|expanded = yes

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{{Componentbox component

|letter = B

|primary = A

|appmag_v = 9.8

|epoch = 2015

|posang= 286

|angdist= 195.8

|ra = {{RA|19|50|40.5}}

|dec = {{DEC|+08|52|13}}

|radec_footnote = {{SIMBAD link|CCDM+19508%2B0852B|BD+08 4236B -- Star in double system}}, database entry, SIMBAD. Accessed online November 25, 2008.

|simbad = CCDM+19508%2B0852B

|expanded = yes

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{{Componentbox component

|letter = C

|primary = A

|appmag_v = 10.3

|epoch = 2015

|posang= 110

|angdist= 186.4

|ra = {{RA|19|51|00.8}}

|dec = {{DEC|+08|50|58}}

|radec_footnote = {{SIMBAD link|CCDM+19508%2B0852C|BD+08 4238 -- Star in double system}}, database entry, SIMBAD. Accessed online November 25, 2008.

|simbad = CCDM+19508%2B0852C

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{{Componentbox component

|letter = D

|primary = A

|appmag_v = 11.9

|epoch = 2015

|posang= 105

|angdist= 26.8

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|radec_footnote =

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{{Componentbox component

|letter = E

|primary = A

|appmag_v = 11.0

|epoch = 2015

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|angdist= 157.3

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|letter = F

|primary = A

|appmag_v = 10.3

|epoch = 2015

|posang= 48

|angdist= 292.4

|ra = {{RA|19|51|02.0}}

|dec = {{DEC|+08|55|33}}

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|simbad = CCDM+19510%2B0856AB

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|letter = G

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|posang= 121

|angdist= 185.1

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|simbad =

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{{Componentbox end}}

• Historical brightest stars
• Lists of stars
• List of brightest stars
• List of nearest bright stars
• List of most luminous stars

{{reflist|group=nb}}

{{Reflist|refs=

{{cite journal |bibcode=2020A&A...633A..78B |title=A realistic two-dimensional model of Altair |last1=Bouchaud |first1=K. |last2=Domiciano De Souza |first2=A. |last3=Rieutord |first3=M. |last4=Reese |first4=D. R. |last5=Kervella |first5=P. |journal=Astronomy and Astrophysics |year=2020 |volume=633 |pages=A78 |doi=10.1051/0004-6361/201936830 |arxiv=1912.03138 |s2cid=208857428 }}

{{Cite journal |last=Rieutord |first=Michel |last2=Reese |first2=Daniel R. |last3=Mombarg |first3=Joey S. G. |last4=Charpinet |first4=Stéphane |date=2024-07-01 |title=An improved asteroseismic age of the rapid rotator Altair from TESS data |journal=Astronomy & Astrophysics |language=en |volume=687 |pages=A259 |doi=10.1051/0004-6361/202449833 |arxiv=2406.09220 |issn=0004-6361}}

{{Cite journal | last1=van Leeuwen | first1=F. | title=Validation of the new Hipparcos reduction | 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 | s2cid=18759600 }}

{{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 }}

{{cite web

| title=HR 7557, database entry

| url=http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/50/catalog&recno=7557

| work=The Bright Star Catalogue | edition=5th Revised Ed. (Preliminary Version)

| first1=D. | last1=Hoffleit | first2=W. H. | last2=Warren, Jr.

| publisher=CDS

| access-date=2008-11-25 }} ID [http://vizier.u-strasbg.fr/viz-bin/Cat?V/50 V/50]

{{SIMBAD link|alf+aql|NAME ALTAIR -- Variable Star of delta Sct type}}, database entry, SIMBAD. Accessed on line November 25, 2008.

{{cite web |url=http://www.daviddarling.info/encyclopedia/A/Altair.html |title=Altair |website=The Internet Encyclopedia of Science |author=David Darling |access-date=2022-08-03 }}

{{cite journal | doi = 10.1086/497981| title = Resolving the Effects of Rotation in Altair with Long-Baseline Interferometry| year = 2006| last1 = Peterson| first1 = D. M.| last2 = Hummel| first2 = C. A.| last3 = Pauls| first3 = T. A.| last4 = Armstrong| first4 = J. T.| last5 = Benson| first5 = J. A.| last6 = Gilbreath| first6 = G. C.| last7 = Hindsley| first7 = R. B.| last8 = Hutter| first8 = D. J.| last9 = Johnston| first9 = K. J.| last10 = Mozurkewich| first10 = D.| last11 = Schmitt| first11 = H.| display-authors=3 | journal = The Astrophysical Journal| volume = 636| issue = 2| pages = 1087–1097| arxiv = astro-ph/0509236| bibcode = 2006ApJ...636.1087P| s2cid = 18683397}} See Table 2 for stellar parameters.

{{Cite journal | title=Altair - the "hottest" magnetically active star in X-rays | last1=Robrade | first1=J. | last2=Schmitt | first2=J. H. M. M. | journal=Astronomy and Astrophysics | volume=497 | issue=2 | pages=511–520 | date=April 2009 | doi=10.1051/0004-6361/200811348 | bibcode=2009A&A...497..511R | arxiv=0903.0966 | s2cid=14320453 }}

{{Cite journal

| title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I

| last1=Gray | first1=R. O. | last2=Corbally | first2=C. J.

| last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T.

| last5=Robinson | first5=P. E. | display-authors=1

| journal=The Astronomical Journal

| volume=126 | issue=4 | pages=2048 | year=2003

| bibcode=2003AJ....126.2048G | doi=10.1086/378365

| arxiv=astro-ph/0308182 | s2cid=119417105 }}

}}

{{Commons category|Altair}}

• [https://web.archive.org/web/20090414054427/http://origins.jpl.nasa.gov/library/story/072501-a.html Star with Midriff Bulge Eyed by Astronomers], JPL press release, July 25, 2001.
• [https://sl.voxastro.org/library/UVES-POP/details/?star=Altair Spectrum of Altair]
• [http://www.astro.lsa.umich.edu/~monnier/Altair2007/altair2007.html Imaging the Surface of Altair], University of Michigan news release detailing the CHARA array direct imaging of the stellar surface in 2007.
• [http://photojournal.jpl.nasa.gov/catalog/PIA04204 PIA04204: Altair], NASA. Image of Altair from the Palomar Testbed Interferometer.
• [http://www.solstation.com/stars/altair.htm Altair], SolStation.
• [http://news.bbc.co.uk/2/hi/science/nature/6709345.stm Secrets of Sun-like star probed], BBC News, June 1, 2007.
• [http://www.astromart.com/news/news.asp?news_id=697 Astronomers Capture First Images of the Surface Features of Altair] {{Webarchive|url=https://web.archive.org/web/20090629063240/http://www.astromart.com/news/news.asp?news_id=697 |date=2009-06-29 }}, Astromart.com
• [http://aladin.u-strasbg.fr/AladinPreview?-c=NAME+ALTAIR&ident=NAME+ALTAIR&submit=Aladin+previewer Image of Altair] from Aladin.

{{Sky|19|50|46.9990|+|08|52|05.959|17}}

{{Nearest systems|4}}

{{Stars of Aquila}}

{{Portal bar|Astronomy|Stars|Outer space}}

{{Authority control}}

{{DEFAULTSORT:Altair}}

Category:A-type main-sequence stars

Category:Delta Scuti variables

4

Category:G-Cloud

Category:Aquila (constellation)

Aquilae, Alpha

7557

BD+08 4236

Aquilae, 53

0768

187642

097649

Altair

Category:TIC objects

Category:Astronomical objects known since antiquity