Lambda Aquilae

Lambda Aquilae, Latinized from λ Aquilae, is a star in the constellation Aquila. It has the traditional name Al Thalimain /ælˌθælɪˈmeɪn/, which it shares with ι Aquilae. The name is derived from the Arabic الظلیمين al-ẓalīmayn "the two ostriches". Lambda Aquilae is more precisely Al Thalimain Prior. It has an apparent visual magnitude of 3.43,[2] which is bright enough to be seen with the naked eye. Parallax measurements place it at a distance of about 125 light-years (38 parsecs) from Earth.[1]

Lambda Aquilae
Location of λ Aquilae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 06m 14.93898s[1]
Declination −04° 52′ 57.2007″[1]
Apparent magnitude (V) 3.43[2]
Characteristics
Spectral type B9Vn[3]
U−B color index −0.27[2]
B−V color index −0.09[2]
Astrometry
Radial velocity (Rv)−12.0[4] km/s
Proper motion (μ) RA: −19.68[1] mas/yr
Dec.: −90.37[1] mas/yr
Parallax (π)26.05 ± 0.81[1] mas
Distance125 ± 4 ly
(38 ± 1 pc)
Absolute magnitude (MV)+0.54[5]
Details
Mass3.1+0.1
−0.1[6] M☉
Radius1.9[7] R☉
Luminosity55[7] L☉
Surface gravity (log g)4.31[7] cgs
Temperature11780[8] K
Metallicity [Fe/H]0.00[6] dex
Rotational velocity (v sin i)103[9] km/s
Age160+20
−20[6] Myr
Other designations
λ Aql, 16 Aql, BD-05° 4876, FK5 717, HD 177756, HIP 93805, HR 7236, SAO 143021.[10]
Database references
SIMBADdata

Properties

Lambda Aquilae is a main sequence star with a stellar classification of B9Vn,[3] which means that, like the Sun, it is generating energy at its core through the nuclear fusion of hydrogen. It is more massive than the Sun, with about three times its mass, and radiates about 55[7] times the Sun's luminosity from its outer envelope at a higher effective temperature of 11,780 K.[8] This temperature gives Lambda Aquilae the blue-white hue that is a characteristic of B-type stars.[11] Lambda Aquilae was one of the least variable stars observed by the Hipparcos satellite. It is a suspected Lambda Boötis star[12] and has an age of about 160 million years.[6]

This star lies about 5° from the galactic plane and about 30° from the line of sight to the Galactic Center. This region of the sky is crowded with other objects along the line of sight, with at least 55 located within 10 arcseconds of the star. Examination of the star shows no companions with an 85% probability.[6] Despite this, it is suspected of being a spectroscopic binary star.[12] That is, it may have an orbiting companion whose presence is revealed by displacements in the absorption lines in the spectrum caused by the Doppler effect. Based upon the width of these lines, the star is rotating rapidly, with a projected rotational velocity of 103 km s−1.[9]

NASA's Pioneer 11 space probe, launched in April 1973, exited the solar system in 1990 and continued in the direction of Lambda Aquilae. It is estimated that it will take around 4 million years for the probe to make its closest approach to its destination, assuming it will remain intact. However, NASA stopped communicating with Pioneer 11 since November 1995 because the space probe's power was already too weak to transmit any data.[13]

Etymology

In Chinese, 天弁 (Tiān Biàn), meaning Market Officer, refers to an asterism consisting of λ Aquilae, α Scuti, δ Scuti, ε Scuti, β Scuti, η Scuti, 12 Aquilae, 15 Aquilae and 14 Aquilae.[14] Consequently, the Chinese name for λ Aquilae itself is 天弁七 (Tiān Biàn qī, English: the Seventh Star of Market Officer.)[15]

This star, together with η Aql, θ Aql, δ Aql, ι Aql and κ Aql made up the obsolete constellation Antinous.[16]

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819
  4. Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, Astronomisches Rechen-Institut Heidelberg, 35 (35): 1, Bibcode:1999VeARI..35....1W
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  6. Janson, Markus; et al. (August 2011), "High-contrast Imaging Search for Planets and Brown Dwarfs around the Most Massive Stars in the Solar Neighborhood", The Astrophysical Journal, 736 (2): 89, arXiv:1105.2577, Bibcode:2011ApJ...736...89J, doi:10.1088/0004-637X/736/2/89, S2CID 119217803
  7. Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M
  8. Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147, S2CID 14969137
  9. Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298
  10. "lam Aql -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-29
  11. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16
  12. Lagrange, A.-M.; et al. (February 2009), "Extrasolar planets and brown dwarfs around A-F type stars. VI. High precision RV survey of early type dwarfs with HARPS", Astronomy and Astrophysics, 495 (1): 335–352, arXiv:0809.4636, Bibcode:2009A&A...495..335L, doi:10.1051/0004-6361:200810105, S2CID 62894956
  13. "Pioneer 10 and 11", Space Topics: Past Missions, The Planetary Society, archived from the original on 2012-01-18, retrieved 2012-02-05
  14. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  15. (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 23, 2010.
  16. Ian Ridpath's Star Tales - Antonious
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