Gliese 105

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Gliese 105 A/B/C
Observation data
Epoch J2000      Equinox J2000
Constellation Cetus
Right ascension A: 02h 36m 04.89s[1] B: 02h 36m 15.0s
C: 02h 35m 58.8s
Declination A: +06° 53′ 12.7″[1]
B: +06° 52′ 18″
C: +06° 52′ 00″
Apparent magnitude (V) 5.82/11.66/16.9
Spectral type K3 V/M3.5 Vn/M7 V
U−B color index 0.81/1.12
B−V color index 0.97/1.60
Variable type None/BY Draconis
Radial velocity (Rv) 25.7 km/s
Proper motion (μ) RA: 1807.78 ± 0.89[1] mas/yr
Dec.: 1444.02 ± 0.40[1] mas/yr
Parallax (π) 139.27 ± 0.45[1] mas
Distance 23.42 ± 0.08 ly
(7.18 ± 0.02 pc)
Absolute magnitude (MV) 6.49/12.34/17.58
Mass 0.81/0.21/0.08 M
Radius 0.650 ± 0.053[2]/0.28 R
Luminosity (bolometric) 0.29/ ? L
Luminosity (visual, LV) 0.22/0.001/0.0000075 L
Temperature 4,841[3] K
Metallicity 85.11%[3]/ ? Z
Rotation ?
Age 4.8-6.6 (Sun=4.6) ×109 years
Other designations
268 G. Cet, Gl 105, CCDM J02361+0653, BD+06° 398
Gliese 105 AC: HR 753, HD 16160, LHS 15, LTT 10858, SAO 110636, FK5 1073, G 73-70, G 76-11, LFT 217, HIP 12114
Gliese 105 B: BX Cet, LHS 16, LTT 10859, G 73-71, G 76-12, LFT 217
Database references
Gl 105 A
Gl 105 B
Gl 105 C
Gliese 105.

Gliese 105 (also known as 268 G. Ceti) is a triple star system in the constellation of Cetus. It is located relatively near the Sun at an estimated distance of less than 24 light years,[1] but even the brightest component is barely visible with the unaided eye (see Bortle scale). No planets have yet been detected around any of the stars in this system.

The companion star B has a common proper motion with A, and the two have an estimated separation of 1,200 AUs. It is a BY Draconis variable star that has been given the designation BX Ceti.

The third companion C lies much closer to A, presently at a distance of approximately 24 AU. The pair A-C have an estimated orbital period of 61 years. C's orbit is estimated to have a high eccentricity of around 0.75 and a semi-major axis of 15 AU,[4] giving an aphelion of 26.25 AU and a perihelion of just 3.75 AU. Component C is a relatively minuscule star that lies at the low end of the mass range needed to achieve nuclear fusion.

From the surface of a theoretical Earth-like planet at 0.55 AU distance from Gliese 105 A, near the inner edge of that star's habitable zone, component C at perihelion would only ever get about half as bright as the full moon does, despite it being a star, and at aphelion it would appear about as bright as Venus becoming barely even visible to the naked eye in the daytime.


  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ van Belle, Gerard T.; von Braun, Kaspar (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". The Astrophysical Journal. 694 (2): 1085–1098. arXiv:0901.1206Freely accessible. Bibcode:2009ApJ...694.1085V. doi:10.1088/0004-637X/694/2/1085. 
  3. ^ a b Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. arXiv:0712.1370Freely accessible. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788. 
  4. ^ Golimowski, David A.; et al. (2000). "The Very Low Mass Component of the Gliese 105 System". The Astronomical Journal. 120 (4): 2082–2088. arXiv:astro-ph/0006230Freely accessible. Bibcode:2000AJ....120.2082G. doi:10.1086/301567. 

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