Altair
Proper names: Altair, Alpha Aquilae, 53 Aquilae
Catalog numbers:
Gliese (Gl) 768, Henry Draper (HD) 187642, Bonner Durchmusterung (BD) +8°4236, Luyten Half-Second (LHS) 3490, Hipparcos Input Catalog (HIC) 97649, Smithsonian Astrophysical Observatory (SAO) 125122, Fifth Fundamental Catalogue (FK5) 745, Hoffleit Bright Star (HR) 7557
Age: less than 1000 million years
Heavy element abundance: 58% of Sol
Arity: singular
Points of interest:
This star is one of the fastest rotating stars known, completing an entire rotation in only 6½ hours (our own sun takes 25 days to rotate once, and isn't as big around). According to Gerard T. Van Belle and collaborators using the Palomar Testbed Interferometer, this spin causes Altair to be 11-17% bigger across at its equator than from pole-to-pole, and to be shaped like a flattened ellipsoid or "oblate spheroid."
Right Ascension and Declination: 19h50m47.002s, +8°52'6.03" (epoch 2000.0)
Distance from Sol: 16.77 light-years (5.143 parsecs)
Standard error in distance: 0.4811%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 7.703, -14.68, 2.586
Galactic (X,Y,Z) coordinates in ly: 11.04, 12.33, -2.728
Proper motion: 0.662 arcsec/yr (54.3° from north)
Radial Velocity: -26.1 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -28.85, -10.19, -2.345
What do all these fields mean?
Spectral class: A7
Luminosity Class: V
Apparent visual magnitude: +0.77
Absolute visual magnitude: +2.21
Visual luminosity: 11.39 x Sol
Variable type: delta Scuti (pulsating variable)
Color indices: B-V= +0.22, U-B= +0.08, R-I= +0.02
Mass: 2 x Sol
Diameter: 1.631 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 3.375 A.U.s
Orbital period in CZ: 4.38376 years
Tidal index in CZ: 0.052036
Angular size of star in sky in CZ: 0.257584 degrees
Data for this star system were most recently updated on 14-April-2004.