AT Microscopii

Catalog numbers:
Gliese (Gl) 799, Henry Draper (HD) 196982, Cordoba Durchmusterung (CD) -32°16135, Hipparcos Input Catalog (HIC) 102141, Smithsonian Astrophysical Observatory (SAO) 212355, UGPMF 502, Luyten Double Star (LDS) 720
Arity: binary
Points of interest:
The orbit calculated by Wilson is the more likely of the two. It gives a combined mass of about 0.6 solar masses for both stars, for an average of 0.3 solar masses each -- an eminently reasonable value for M4.5 dwarfs. The Mourao orbit suggests a rather ludicrous combined mass of over 6 solar masses.

Right Ascension and Declination: 20h41m51.16s, -32°26'7.8" (epoch 2000.0)
Distance from Sol: 33.3 light-years (10.2 parsecs)
Standard error in distance: 4.5388%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 18.3, -21.4, -17.9
Galactic (X,Y,Z) coordinates in ly: 26.1, 5.33, -20.0
Proper motion: 0.429 arcsec/yr (140.5° from north)
Radial Velocity: -4 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -10.1, -15.3, -10.6

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: +10.19
Combined visual luminosity: 0.0073 x Sol
Period: 239.57 years
Semimajor Axis: 71.1 A.U.s
Eccentricity: 0.83
Periastron distance: 12.1 A.U.s
Apastron distance: 130 A.U.s
Year in which periastron occurs: 1920.69
Source for orbit data: R.R.F. Mourao
As seen from A:
     At periastron, B would appear as magnitude -15.21
     At apastron, B would appear as magnitude -10.05
As seen from B:
     At periastron, A would appear as magnitude -15.22
     At apastron, A would appear as magnitude -10.06

Data for A and B's orbit, take 2:
Period: 675 years
Semimajor Axis: 65.4 A.U.s
Eccentricity: 0.6
Periastron distance: 26.2 A.U.s
Apastron distance: 105 A.U.s
Year in which periastron occurs: 1894
Source for orbit data: R.H. Wilson
As seen from A:
     At periastron, B would appear as magnitude -13.53
     At apastron, B would appear as magnitude -10.52
As seen from B:
     At periastron, A would appear as magnitude -13.54
     At apastron, A would appear as magnitude -10.53

Component A:
Proper names: AT Microscopii
Spectral class: M4.5e
Luminosity Class: V
Apparent visual magnitude: +10.99 (increasing to +9.49)
Absolute visual magnitude: +10.94 (increasing to +9.44)
Visual luminosity: 0.0037 x Sol (increasing to 0.015 x Sol)
Variable type: UV Ceti flare star (eruptive variable)
Diameter: 0.41 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.060 A.U.s
Angular size of star in sky in CZ: 3.614104 degrees

Component B:
Proper motion: 0.429 arcsec/yr (140.5° from north)
Radial Velocity: -3 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -9.31, -15.2, -11.2
Spectral class: M4.5e
Luminosity Class: V
Apparent visual magnitude: +11.00
Absolute visual magnitude: +10.95
Visual luminosity: 0.0036 x Sol
Diameter: 0.37 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.060 A.U.s
Angular size of star in sky in CZ: 3.276563 degrees

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