Lambda Aquilae

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Lambda Aquilae
Diagram showing star positions and boundaries of the Aquila constellation and its surroundings
Cercle rouge 100%.svg

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
Distance 125 ± 4 ly
(38 ± 1 pc)
Details
Mass 3.1+0.1
−0.1
[5] M
Radius 1.9[6] R
Luminosity 55[6] L
Surface gravity (log g) 4.31[6] cgs
Temperature 11780[7] K
Metallicity [Fe/H] 0.00[5] dex
Rotational velocity (v sin i) 103[8] km/s
Age 160+20
−20
[5] Myr
Other designations
16 Aql, BD-05° 4876, FK5 717, HD 177756, HIP 93805, HR 7236, SAO 143021.[9]

Lambda Aquilae (λ Aql, λ Aquilae) is a star in the constellation Aquila. It has the traditional name Al Thalimain, which it shares with ι Aquilae. The name is derived from the Arabic الثالمين al-thalīmain "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]

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.[10] Consequently, λ Aquilae itself is known as 天弁七 (Tiān Biàn qī, English: the Seventh Star of Market Officer.)[11]

Properties[edit]

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[6] times the Sun's luminosity from its outer envelope at a higher effective temperature of 11,780 K.[7] This temperature gives Lambda Aquilae the blue-white hue that is a characteristic of B-type stars.[12] Lambda Aquilae was one of the least variable stars observed by the Hipparcos satellite. It is a suspected Lambda Boötis star[13] and has an age of about 160 million years.[5]

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.[5] Despite this, it is suspected of being a spectroscopic binary star.[13] 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.[8]

Related space mission[edit]

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.[14]

References[edit]

  1. ^ a b c d e f 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 
  2. ^ a b c d 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. ^ a b 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. ^ a b c d e 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 
  6. ^ a b c d 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 
  7. ^ a b 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, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147 
  8. ^ a b 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 
  9. ^ "lam Aql -- Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2011-12-29 
  10. ^ (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.
  11. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  13. ^ a b 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 
  14. ^ "Pioneer 10 and 11", Space Topics: Past Missions (The Planetary Society), retrieved 2012-02-05 

External links[edit]