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Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Carina
Right ascension 11h 06m 51.19s[1]
Declination −61° 11′ 10.1″[1]
Spectral type F (primary)/M (b)[2]
Apparent magnitude (I) 15.40 (system)[1]
Variable type Eclipsing binary
Distance 5000 ± 1000 ly
(1600 ± 400[2] pc)
Period (P) 1.804[2] days
Semi-major axis (a) 0.031 ± 0.002 AU[2]
Eccentricity (e) 0[2]
Inclination (i) 86–90°[2]°
Mass 1.3 M
Radius 1.55 R
Temperature 6700 ± 300 K
Mass 0.085 M
Radius 0.13 R
Other designations
V816 Car, 2MASS J11065112-6111103
Database references

OGLE-TR-123 is a binary stellar system containing one of the smallest main-sequence stars whose radius has been measured. It was discovered when the Optical Gravitational Lensing Experiment (OGLE) survey observed the smaller star eclipsing the larger primary. The orbital period is approximately 1.80 days.[2]

The smaller star, OGLE-TR-123b, is estimated to have a radius around 0.13 solar radii, and a mass of around 0.085 solar masses (M), or approximately 90 times Jupiter's. OGLE-TR-123b's mass is close to the lowest possible mass, estimated to be around 0.07 or 0.08 M, for a hydrogen-fusing star.[3] OGLE-TR-123b is the second star with mass less than 0.1 M whose radius has been directly measured; the first such star was the similar OGLE-TR-122b.[2]


  1. ^ a b c The Optical Gravitational Lensing Experiment. Additional Planetary and Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational Campaigns, A. Udalski, G. Pietrzynski, M. Szymanski, M. Kubiak, K. Zebrun, I. Soszynski, O. Szewczyk, and L. Wyrzykowski, Acta Astronomica 53 (June 2003), pp. 133–149.
  2. ^ a b c d e f g h i Radius and mass of a transiting M dwarf near the hydrogen-burning limit. OGLE-TR-123, F. Pont, C. Moutou, F. Bouchy, R. Behrend, M. Mayor, S. Udry, D. Queloz, N. Santos, and C. Melo, Astronomy and Astrophysics 447, #3 (March 1, 2006), pp. 1035–1039. doi:10.1051/0004-6361:20053692. Bibcode2006A&A...447.1035P.
  3. ^ Theory of Low-Mass Stars and Substellar Objects, Gilles Chabrier and Isabelle Baraffe, Annual Review of Astronomy and Astrophysics 38 (2000), pp. 337–377.