Altair

Coordinates: Sky map 19h 50m 46.9990s, +08° 52′ 05.959″
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This article is about a star in the constellation Aquila. For other uses, see Altair (disambiguation).

Altair
Location of Altair (circled)
Observation data
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]
Distance
16.73 ± 0.05 ly
(5.13 ± 0.01 pc)
Absolute magnitude (MV)2.22[6]
Details
Myr
NLTT 48314[7][12][13]
Database references
SIMBADdata

Altair is the brightest

G-cloud—a nearby interstellar cloud, an accumulation of gas and dust.[17][18]

Altair rotates rapidly, with a velocity at the

interferometric studies with multiple telescopes, operating in the infrared, have imaged and confirmed this phenomenon.[11]

Nomenclature

Altair is the brightest star in the constellation Aquila.

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 النسر الطائر Al-Nisr Al-Ṭa'ir, "the flying eagle".[21]

In 2016, the

Working Group on Star Names (WGSN)[22] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[23] 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.[24]

Physical characteristics

Altair in comparison with the Sun

Along with

γ Aquilae, Altair forms the well-known line of stars sometimes referred to as the Family of Aquila or Shaft of Aquila.[16]
: 190 

Altair is a

oblate; its equatorial diameter is over 20 percent greater than its polar diameter.[11]

A light curve for Altair, adapted from Buzasi et al. (2005)[6]

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.[6] 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.[6] 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.[19]

Rotational effects

Direct image of Altair, taken with the CHARA array

The angular diameter of Altair was measured

milliarcseconds.[25] 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.[20]

Theory predicts that, owing to Altair's rapid rotation, its

VLTI.[27]

Altair is one of the few

solar radii, and the polar radius 1.63 solar radii—a 25% increase of the stellar radius from pole to equator.[11] The polar axis is inclined by about 60° to the line of sight from the Earth.[19]

Etymology, mythology and culture

Altair

The term Al Nesr Al Tair appeared in

γ Aquilae and probably goes back to the ancient Babylonians and Sumerians, who called Altair "the eagle star".[2]: 17–18  The spelling Atair has also been used.[30] Medieval astrolabes of England and Western Europe depicted Altair and Vega as birds.[31]

The

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.[32]: 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.[32]
: 115 

In Chinese belief, the asterism consisting of Altair, β Aquilae and γ Aquilae is known as Hé Gǔ (河鼓; lit. "river drum").

γ Aquilae) are separated from respectively their wife and mother Zhinu (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.[35][36]

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".[37]

In Western astrology, the star was ill-omened, portending danger from reptiles.[30]

This star is one of the asterisms used by Bugis sailors for navigation, called bintoéng timoro, meaning "eastern star".[38]

A group of Japanese scientists sent a radio signal to Altair in 1983 with the hopes of contacting extraterrestrial life.[39]

NASA announced Altair as the name of the

Lunar Surface Access Module (LSAM) on December 13, 2007.[40] The Russian-made Beriev Be-200 Altair seaplane is also named after the star.[41]

Visual companions

The bright primary

multiple star designation WDS 19508+0852A and has several faint visual companion stars, WDS 19508+0852B, C, D, E, F and G.[13] All are much more distant than Altair and not physically associated.[42]

Multiple/double star designation: WDS 19508+0852[13]
Component Primary
J2000.0
J2000.0
 Epoch of
observed
separation		 Angular
distance
from
primary		 Position
angle
(relative
to primary)		 Apparent
magnitude
(V)		 Database
reference
B A 19h 50m 40.5s+08° 52′ 13″[43] 2015 195.8
″
 286° 9.8 SIMBAD
C A 19h 51m 00.8s+08° 50′ 58″[44] 2015 186.4
″
 110° 10.3 SIMBAD
D A 2015 26.8
″
 105° 11.9
E A 2015 157.3
″
 354° 11.0
F A 19h 51m 02.0s+08° 55′ 33″ 2015 292.4
″
 48° 10.3 SIMBAD
G A 2015 185.1
″
 121° 13.0

See also

Notes

  1. ^ a b Owing to its rapid rotation, Altair's radius is larger at its equator than at its poles; it is also cooler at the equator than at the poles.
  2. ^ From values of v sin i and i in the second column of Table 1, Monnier et al. 2007.

References

  1. ^ "Altair: definition of Altair in Oxford dictionary (American English)". Archived from the original on May 12, 2014.
  2. ^
    ISBN 978-1-931559-44-7
    .
  3. ^
    S2CID 18759600
  4. ^
    Bibcode:2002yCat.2237....0D
    .
  5. S2CID 119417105
    .
  6. ^
    S2CID 16524681
    .
  7. ^ a b c NAME ALTAIR -- Variable Star of delta Sct type, database entry, SIMBAD. Accessed on line November 25, 2008.
  8. ^
    S2CID 208857428
    .
  9. ^
    S2CID 18683397
    . See Table 2 for stellar parameters.
  10. Bibcode:1990A&AS...85.1015M
  11. ^
    S2CID 4615273
    . See second column of Table 1 for stellar parameters.
  12. CDS ID V/50
    . Accessed on line November 25, 2008.
  13. ^ a b c Entry 19508+0852, The Washington Double Star Catalog Archived 2009-01-31 at the Wayback Machine, United States Naval Observatory. Accessed online November 25, 2008.
  14. ^ David Darling. "Altair". The Internet Encyclopedia of Science. Retrieved 2022-08-03.
  15. ^ Darling, David. "Summer Triangle". www.daviddarling.info. Retrieved 2008-11-26.
  16. ^
    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. ^
    S2CID 14320453
    .
  20. ^
    S2CID 13969695
    .
  21. ^ "the definition of altair". www.dictionary.com. Retrieved 2018-09-30.
  22. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  23. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved 28 July 2016.
  24. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  25. doi:10.1093/mnras/137.4.393
    .
  26. S2CID 15857535
    .
  27. doi:10.1051/0004-6361:20042476
    .
  28. ^ a b "Gazing up at the Man in the Star?" (Press release). National Science Foundation. May 31, 2007. Retrieved 2022-08-03.
  29. doi:10.1093/mnras/55.8.429
    .
  30. ^ a b c Allen, Richard Hinckley (1899). Star-names and their meanings. unknown library. New York, Leipzig [etc.] G.E. Stechert. pp. 59–60.
  31. S2CID 84102853
    .
  32. ^
    ISBN 1-85538-306-3
    .
  33. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 26, 2008.
  34. ^ Mayers, William Frederick (1874). The Chinese reader's manual: A handbook of biographical, historical ... Harvard University. American Presbyterian Mission Press. pp. 97–98, 161.
  35. ^
    ISBN 978-1-4196-4893-9
    .
  36. ISBN 978-1-59158-294-6
    .
  37. ISBN 978-1-921313-19-6
    .
  38. ISBN 978-1-4419-7623-9
    .
  39. ^ "'Anybody there?' Astronomers waiting for a reply from Altair". August 20, 2023. Retrieved 2023-08-25.
  40. ^ "NASA names next-gen lunar lander Altair". .collectSPACE. December 13, 2007. Retrieved 2022-08-03.
  41. Beriev Aircraft Company. February 12, 2003. Archived from the original
    on 2021-11-05. Retrieved 2022-08-03.
  42. doi:10.1051/0004-6361/201833051
    .
  43. ^ BD+08 4236B -- Star in double system, database entry, SIMBAD. Accessed online November 25, 2008.
  44. ^ BD+08 4238 -- Star in double system, database entry, SIMBAD. Accessed online November 25, 2008.

External links

Wikimedia Commons has media related to Altair.


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