Gliese 229

light-years

Catalog numbers:
     Gliese (Gl) 229, Henry Draper (HD) 42581, Bonner Durchmusterung (BD) -21°1377, Luyten Half-Second (LHS) 1827, Hipparcos Input Catalog (HIC) 29295, Smithsonian Astrophysical Observatory (SAO) 171334, Vyssotsky McCormick (McC) 471, New Suspected Variable (NSV) 2863
Age: 3000 million years
Standard error in age: 33%
Source for age: Apr. 2000 Scientific American, p. 82
Arity: singular, with a brown dwarf companion
Points of interest:
     In late 1995, the existence of an extremely dim, cool companion (luminosity no higher than 0.000006 x Sol, surface temperature less than 1200 K) was confirmed by several joint observations.  This companion, dubbed Gliese 229B, is most likely a brown dwarf: a star-like object too small to sustain nuclear fusion reactions in its core.  Its mass is 20-50 times that of Jupiter (0.03-0.07 x Sol), although close-up Hubble Space Telescope photographs show a disc that would give it only about the same diameter as Jupiter.  Its orbital period is so long that no accurate measurements of the shape of its orbit have yet been made; at last sighting, it was 44 A.U.s away from the main star.  Theoretically, a solid planet orbiting Gliese 229B at a very short distance (300 000 km) would receive as much energy from it as the Earth does from our own sun; however, brown dwarfs cool off with age, and so such a planet wouldn’t remain warm for very long.
     Since the main star itself is a flare star, it is probably incapable of harboring planets with surface life as we know it.

Right Ascension and Declination: 6h10m34.617s, -21°51'53.51" (epoch 2000.0)
Distance from Sol: 18.83 light-years (5.774 parsecs)
Standard error in distance: 0.6425%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: -0.806, 17.46, -7.014
Galactic (X,Y,Z) coordinates in ly: -11.79, -13.48, -5.817
Proper motion: 0.737 arcsec/yr (190.2° from north)
Radial Velocity: 5.2 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: 11.69, -12.26, -12.12

What do all these fields mean?


Spectral class: M1n
Luminosity Class: V
Apparent visual magnitude: +8.15
Absolute visual magnitude: +9.34
Visual luminosity: 0.0160 x Sol
Variable type: UV Ceti flare star (eruptive variable)
Color indices: B-V= +1.50, U-B= +1.23, R-I= +0.82
Mass: 0.46 x Sol
Diameter: 0.527 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.126 A.U.s
Orbital period in CZ: 24.1915 days
Tidal index in CZ: 227.958
Angular size of star in sky in CZ: 2.225287 degrees
Detected companions: 1
Companion b:
     Mass: 45 x Jupiter
     Standard error in mass: 44.4%
     Source for mass: Allard et al. (1996)
     Diameter: 1 x Jupiter
     Standard error in diameter: 10%
     Source for diameter: Marley et al. (1996)
     Observed Separation: 44 A.U.s
     Source for orbit data: Allard & Marley

light-years
but not more than light-years away
Data for this star system were most recently updated on 4-April-2001.