Altair

This article is about a star in the constellation Aquila. For other uses, see Altair (disambiguation).

Altair
Location of Altair (circled)
Observation data
Epoch J2000.097      Equinox J2000.0 (ICRS)
Constellation Aquila
Pronunciation /ˈæltɛər/, /ˈæltaɪər/[1][2]
Right ascension 19h 50m 46.99855s[3]
Declination +08° 52′ 05.9563″[3]
Apparent magnitude (V) 0.76[4]
Characteristics
Evolutionary stage Main sequence
Spectral type A7Vn[5]
U−B color index +0.09[4]
B−V color index +0.22[4]
V−R color index +0.14[4]
R−I color index +0.13[4]
Variable type Delta Scuti[6]
Astrometry
Radial velocity (Rv)−26.1±0.9[7] km/s
Proper motion (μ) RA: +536.23[3] mas/yr
Dec.: +385.29[3] mas/yr
Parallax (π)194.95 ± 0.57 mas[3]
Distance16.73 ± 0.05 ly
(5.13 ± 0.01 pc)
Absolute magnitude (MV)2.22[6]
Details
Mass1.86±0.03[8] M☉
Radius1.57 – 2.01[8][nb 1] R☉
Luminosity10.6[9] L☉
Surface gravity (log g)4.29[10] cgs
Temperature6,860 – 8,621[8][nb 1] K
Metallicity [Fe/H]−0.2[11] dex
Rotation7.77 hours[9]
Rotational velocity (v sin i)242[8] km/s
Age100[8] Myr
Other designations
Atair, α Aquilae, α Aql, Alpha Aquilae, Alpha Aql, 53 Aquilae, 53 Aql, BD+08°4236, FK5 745, GJ 768, HD 187642, HIP 97649, HR 7557, SAO 125122, WDS 19508+0852A, LFT 1499, LHS 3490, LTT 15795, NLTT 48314[7][12][13]
Database references
SIMBADdata

Altair is the brightest star in the constellation of Aquila and the twelfth-brightest star in the night sky. It has the Bayer designation Alpha Aquilae, which is Latinised from α Aquilae and abbreviated Alpha Aql or α Aql. Altair is an A-type main-sequence star with an apparent visual magnitude of 0.77 and is one of the vertices of the Summer Triangle asterism; the other two vertices are marked by Deneb and Vega.[7][14][15] It is located at a distance of 16.7 light-years (5.1 parsecs) from the Sun.[16]: 194  Altair is currently in the G-cloud—a nearby interstellar cloud, an accumulation of gas and dust.[17][18]

Altair rotates rapidly, with a velocity at the equator of approximately 286 km/s.[nb 2][11] This is a significant fraction of the star's estimated breakup speed of 400 km/s.[19] 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.[20] Other interferometric studies with multiple telescopes, operating in the infrared, have imaged and confirmed this phenomenon.[11]

  1. ^ "Altair: definition of Altair in Oxford dictionary (American English)". Archived from the original on May 12, 2014.
  2. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  3. ^ a b c d e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  4. ^ a b c d e Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  5. ^ Cite error: The named reference gray_et_al_2003 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Buzasi et al 2005 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference sb0 was invoked but never defined (see the help page).
  8. ^ a b c d e Cite error: The named reference bouchaud2020 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference peterson06 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference aass85_3_1015 was invoked but never defined (see the help page).
  11. ^ a b c Monnier, J. D.; Zhao, M; Pedretti, E; Thureau, N; Ireland, M; Muirhead, P; Berger, J. P.; Millan-Gabet, R; Van Belle, G; Ten Brummelaar, T; McAlister, H; Ridgway, S; Turner, N; Sturmann, L; Sturmann, J; Berger, D (2007). "Imaging the surface of Altair". Science. 317 (5836): 342–345. arXiv:0706.0867. Bibcode:2007Sci...317..342M. doi:10.1126/science.1143205. PMID 17540860. S2CID 4615273. See second column of Table 1 for stellar parameters.
  12. ^ Cite error: The named reference bsc1 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference wds was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference darlingaltair was invoked but never defined (see the help page).
  15. ^ Darling, David. "Summer Triangle". www.daviddarling.info. Retrieved 2008-11-26.
  16. ^ Hoboken, Fred Schaaf (2008). The brightest stars : discovering the universe through the sky's most brilliant stars. New Jersey: John Wiley & Sons, Inc. ISBN 978-0-471-70410-2. OCLC 440257051.
  17. ^ "Our Local Galactic Neighborhood". NASA. Archived from the original on 2013-11-21.
  18. ^ Gilster, Paul (2010-09-01). "Into the Interstellar Void". Centauri Dreams. Retrieved 2017-03-26.
  19. ^ Cite error: The named reference robrade2009 was invoked but never defined (see the help page).
  20. ^ Belle, Gerard T. van; Ciardi, David R.; Thompson, Robert R.; Akeson, Rachel L.; Lada, Elizabeth A. (2001). "Altair's Oblateness and Rotation Velocity from Long-Baseline Interferometry". The Astrophysical Journal. 559 (2): 1155–1164. Bibcode:2001ApJ...559.1155V. doi:10.1086/322340. ISSN 0004-637X. S2CID 13969695.


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