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Altair

Altair Altair in the constellation of Aquila. Observation data Epoch J2000.0      Equinox J2000.0 (ICRS) Constellation Aquila Right ascension 19h 50m 46.99855s Declination +08° 52' 05.9563? Apparent magnitude (V) 0.77 Characteristics Spectral type A7 V U-B color index +0.08 B-V color index +0.22 V-R color index 0.0 R-I color index +0.14 Variable type Delta Scuti Astrometry Radial velocity (Rv) -26.1 ± 0.9 km/s Proper motion (µ) RA: +536.23 mas/yr Dec.: +385.29 mas/yr Parallax (p) 194.95 ± 0.57 mas Distance 16.73 ± 0.05 ly (5.13 ± 0.01 pc) Absolute magnitude (MV) 2.21 Details Mass 1.79 M? Radius 1.63 to 2.03 R? Luminosity 10.6 L? Surface gravity (log g) 4.29 cgs Temperature 6,900 to 8,500 K Metallicity -0.2 dex Rotation 8.9 hours Rotational velocity (v sin i) 240 km/s Age  Gyr Other designations Database references SIMBAD data Altair (Alpha Aquilae, Alpha Aql, a Aquilae, a Aql, Atair) is the brightest star in the constellation Aquila and the twelfth brightest star in the night sky. It is currently in the G-cloud. 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 (the other two vertices are marked by Deneb and Vega).Altair rotates rapidly, with a velocity at the equator of approximately 286 km/s. 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. Other interferometric studies with multiple telescopes, operating in the infrared, have imaged and confirmed this phenomenon. ^ Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page). ^ Cite error: The named reference sb0 was invoked but never defined (see the help page). ^ Cite error: The named reference bsc1 was invoked but never defined (see the help page). ^ a b c d e f g Imaging the Surface of Altair, J. Monnier et al., Science 317, #5836 (July 20, 2007), pp. 342–345, doi:10.1126/science.1143205, Bibcode: 2007Sci...317..342M, PubMed 17540860. Accessed on line November 25, 2008. See second column of Table 1 for stellar parameters. ^ Cite error: The named reference peterson06 was invoked but never defined (see the help page). ^ Cite error: The named reference aass85_3_1015 was invoked but never defined (see the help page). ^ Cite error: The named reference darlingaltair was invoked but never defined (see the help page). ^ Cite error: The named reference wds was invoked but never defined (see the help page). ^ http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/neighborhood.html, Our Local Galactic Neighborhood, NASA ^ http://www.centauri-dreams.org/?p=14203, Into the Interstellar Void, Centauri Dreams ^ Summer Triangle, entry, The Internet Encyclopedia of Science, David Darling. Accessed on line November 26, 2008. ^ Altair's Oblateness and Rotation Velocity from Long-Baseline Interferometry, Gerard T. van Belle, David R. Ciardi, Robert R. Thompson, Rachel L. Akeson, and Elizabeth A. Lada, Astrophysical Journal 559 (October 1, 2001), pp. 1155–1164, doi:10.1086/322340, Bibcode: 2001ApJ...559.1155V. Cite error: There are tags on this page, but the references will not show without a {{reflist|group=nb}} template (see the help page).
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