HD 203857

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HD 203857
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 21h 21m 46.81s
Declination +37° 08′ 10.2″
Apparent magnitude (V) 6.45
Spectral type K5III
Distance≈919.32 ly
(282±50 pc)
Mass1.7 [1] M
Radius46-50[1] R
Luminosity513[1] L
Temperature3980[1] K
Other designations
HD 203857, HIP 105637, SAO 71280, HR 8193, BD+36° 4543, CCDM J21237+3722A
Database references

HD 203857 is a late type K giant star in the constellation Cygnus, located nearly 920 light years away from the Sun. The star is thought to form a visual binary system with the F-type bright giant BDS 10966 A, though it's likely they are actually not gravitationally bound. The star likely hosts an extrasolar planet, though yet unconfirmed.

Substellar companion[edit]

Okayama Planet Search team has published a paper in late 2008 reporting investigations on radial velocity variations observed for a set of evolved stars, announcing possible detection of a substellar companion orbiting the giant star HD 203857.[1] Orbital period is estimated 2.3 years, but planet has still to be confirmed.

The HD 203857 planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (unconfirmed) ≥8.1 MJ 2.1 836.8 0.3


  1. ^ a b c d e 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.

External links[edit]