Epsilon Eridani

light-years
Proper names: Epsilon Eridani, 18 Eridani
Catalog numbers:
     Gliese (Gl) 144, Henry Draper (HD) 22049, Bonner Durchmusterung (BD) -9697 , Luyten Half-Second (LHS) 1557 , Hipparcos Input Catalog (HIC) 16537, Smithsonian Astrophysical Observatory (SAO) 130564, Fifth Fundamental Catalogue (FK5) 127, Hoffleit Bright Star (HR) 1084
Heavy element abundance: 59% of Sol
Standard error in heavy element abundance: 5%
Source for heavy element abundance: Strobel [Fe/H] Determinations
Arity: an unseen companion is suspected
Points of interest:
     In addition to the Jupiter-mass planet discovered around this star on August 7, 2000 at the University of Texas MacDonald Observatory, tiny wobbles in the position of Epsilon Eridani also suggest that a second invisible companion is orbiting this star farther out.  Such a companion would be 1.07 light-hours (7.7 AUs) away, orbit the main star once every 25 years, and have a mass less than 0.05 x Sol.  It is debatable whether this object would be a brown dwarf or a star too dim to be seen from an Earth-based telescope.
     Asymmetric, primordial dust rings made up of 1-millimeter-size particles extend 60 AUs from this star.  The irregular shape of this ring may be due to yet another undiscovered planet orbiting just inside the ring, at 30 AUs.
     As of the late 1990s, this is officially the star about which Babylon 5 orbits.

Right Ascension and Declination: 3h32m55.846s, -9°27'29.72" (epoch 2000.0)
Distance from Sol: 10.50 light-years (3.218 parsecs)
Standard error in distance: 0.2728%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 6.197, 8.294, -1.725
Galactic (X,Y,Z) coordinates in ly: -6.820, -1.966, -7.733
Proper motion: 0.98 arcsec/yr (271.1° from north)
Radial Velocity: 16.9 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -4.150, 6.971, -21.06

What do all these fields mean?


Spectral class: K2
Luminosity Class: V
Apparent visual magnitude: +3.73
Absolute visual magnitude: +6.19
Visual luminosity: 0.292 x Sol
Variable type: BY Draconis (rotating variable)
Color indices: B-V= +0.88, U-B= +0.58, R-I= +0.30
Mass: 0.85 x Sol
Source for mass: Cochran
Diameter: 0.865 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.540 A.U.s
Orbital period in CZ: 157.197 days
Tidal index in CZ: 5.39876
Angular size of star in sky in CZ: 0.853643 degrees
Detected companions: 1
Companion b:
     Mass: 1.2 x Jupiter
     Standard error in mass: 33%
     Source for mass: William Cochran et al. (2000)
     Period: 7.064 years
     Semimajor Axis: 3.4 A.U.s
     Eccentricity: 0.6
     Periastron distance: 1.36 A.U.s
     Apastron distance: 5.44 A.U.s
     Source for orbit data: Cochran et al.

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