Upsilon1 Hydrae

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Upsilon1 Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 09h 51m 28.6937s
Declination −14° 50′ 47.771″
Apparent magnitude (V) 4.12
Spectral type G6/8III[1]
Distance 273.48 ly
(83.89 pc)
Mass 3.34 [1] M
Radius 17.1 R
Luminosity 174[1] L
Temperature 5045[1] K
Age 270[1] million years
Other designations
υ1 Hya, 39 Hya, HD 85444, BD-14° 2963, HIP 48356, HR 3903, SAO 155542.
Database references

Upsilon1 Hydrae is a yellow giant star in the constellation of Hydra. The star is one of Okayama Planet Search's main target for planet search and has turned out to host a substellar companion.

Substellar companion[edit]

The Okayama Planet Search team published a paper in 2005 reporting investigations on radial velocity variations observed for a set of class G giants and announcing the detection of a brown dwarf companion in an eccentric orbit around Upsilon1 Hydrae.[2] The orbital period is roughly 4.1 years.

The Upsilon1 Hydrae planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b ≥49 MJ 3.9 1500 0.57


  1. ^ a b c d e Takeda; et al. (2008). "Stellar Parameters and Elemental Abundances of Late-G Giants". Publications of the Astronomical Society of Japan. 60 (4): 781–802. Bibcode:2008PASJ...60..781T. arXiv:0805.2434Freely accessible. doi:10.1093/pasj/60.4.781. 
  2. ^ Sato; et al. (2005). "Radial-Velocity Variability of G-Type Giants: First Three Years of the Okayama Planet Search Program". Publications of the Astronomical Society of Japan. 57 (1): 97–107. Bibcode:2005PASJ...57...97S. doi:10.1093/pasj/57.1.97.