27 Hydrae

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27 Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension  09h 20m 29.0181s
Declination −09° 33′ 20.501″
Apparent magnitude (V) 4.82
Spectral type G8III-IV/?M5V
B−V color index 0.92
Distance243.4 ly
(74.68 pc)
Mass2.32/≥0.25 M
Radius≈8/0.3? R
Luminosity40.3/0.0074? L
Temperature5150/>3100? K
Period (P)≈1.6 million yr
Semi-major axis (a)15,800 AUs
Other designations
27 Hya, HD 80586, BD -08° 2643, HIP 45811, HR 3709, SAO 136768.
Database references

27 Hydrae is an evolved yellow giant star in the constellation of Hydra. The star is suspected to host a low-mass companion.

Substellar companion[edit]

The Okayama Planet Search team published a paper in late 2008 reporting investigations into radial velocity variations observed for a set of evolved stars, showing hints of a substellar companion orbiting the wide binary system 27 Hydrae.[1] The orbital period is estimated at 9.3 years, but no planet has been confirmed yet.

The 27 Hydrae planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (unconfirmed) ≥10 MJ ≈5.9 3400 ?


  1. ^ Toyota; et al. (2008). "Radial Velocity Search for Extrasolar Planets in Visual Binary Systems". Publications of the Astronomical Society of Japan. 61 (1): 19–28. Bibcode:2009PASJ...61...19T. doi:10.1093/pasj/61.1.19.