P Eridani

Proper names: P Eridani
Catalog numbers:
Gliese (Gl) 66, Dunlop (DUN) 5
Arity: binary
Points of interest:
Either the luminosity data or the orbital data for this star are in error. According to the semimajor axis and the orbital period, these stars should have a total mass of 0.62 x Sol combined. However, their luminosities indicate that 0.62 solar masses should be the mass of just the A star by itself, which would also be consistent with what one would expect as the mass of an early class K main-sequence star.

Right Ascension and Declination: 1h39m47.8s, -56°11'41" (epoch 2000.0)
Distance from Sol: 26.6 light-years (8.15 parsecs)
Standard error in distance: 1.1356%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 13.4, 6.24, -22.1
Galactic (X,Y,Z) coordinates in ly: 4.33, -12.6, -23.0
Proper motion: 0.278 arcsec/yr (84.6° from north)
Radial Velocity: 19.5 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -5.61, -15.2, -15.2

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: +5.54
Combined visual luminosity: 0.53 x Sol
Period: 483.66 years
Semimajor Axis: 63.7 A.U.s
Eccentricity: 0.534
Periastron distance: 29.7 A.U.s
Apastron distance: 97.7 A.U.s
Year in which periastron occurs: 1813.49
Source for orbit data: G.B. van Albada
As seen from A:
     At periastron, B would appear as magnitude -17.86
     At apastron, B would appear as magnitude -15.28
As seen from B:
     At periastron, A would appear as magnitude -17.96
     At apastron, A would appear as magnitude -15.38

Component A:
Catalog numbers:
Henry Draper (HD) 10361, Cape Photographic Durchmusterung (CPD) -56°329, Smithsonian Astrophysical Observatory (SAO) 232490, Hoffleit Bright Star (HR) 487, Cordoba Durchmusterung (CD) -56°329
Spectral class: K2
Luminosity Class: V
Apparent visual magnitude: +5.80
Absolute visual magnitude: +6.25
Visual luminosity: 0.28 x Sol
Color indices: B-V= +0.86, U-B= +0.57, R-I= +0.30
Mass: 0.62 x Sol
Diameter: 0.79 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.53 A.U.s
Orbital period in CZ: 176.946 days
Tidal index in CZ: 4.26088
Angular size of star in sky in CZ: 0.800720 degrees

Component B:
Catalog numbers:
Henry Draper (HD) 10360, Cordoba Durchmusterung (CD) -56°328, Hipparcos Input Catalog (HIC) 7751, Smithsonian Astrophysical Observatory (SAO) 232492, Hoffleit Bright Star (HR) 486
Right Ascension and Declination: 1h39m47.76s, -56°11'41.8" (epoch 2000.0)
Celestial (X,Y,Z) coordinates in ly: 13.4, 6.24, -22.1
Galactic (X,Y,Z) coordinates in ly: 4.33, -12.6, -23.0
Proper motion: 0.278 arcsec/yr (84.6° from north)
Radial Velocity: 22.5 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -5.12, -16.7, -17.8
Spectral class: K3
Luminosity Class: V
Apparent visual magnitude: +5.90
Absolute visual magnitude: +6.35
Visual luminosity: 0.25 x Sol
Color indices: B-V= +0.80, U-B= +0.60, R-I= +0.31
Mass: 0.6 x Sol
Diameter: 1.03 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.50 A.U.s
Orbital period in CZ: 167.865 days
Tidal index in CZ: 4.73436
Angular size of star in sky in CZ: 1.096528 degrees

Data for this star system were most recently updated on 4-April-2001.