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HD 139357 b
Extrasolar planet List of extrasolar planets
Parent star
Star HD 139357
Constellation Draco
Right ascension (α) 15h 35m 16.1992s
Declination (δ) +53° 55′ 19.717″
Apparent magnitude (mV) 5.977
Distance 396.0 ± 26.7 ly
(121.4 ± 8.2 pc)
Spectral type K4III
Orbital elements
Semimajor axis (a) 2.36 ± 0.2 AU
Periastron (q) 2.12 AU
Apastron (Q) 2.60 AU
Eccentricity (e) 0.1 ± 0.02
Orbital period (P) 1125.7 ± 9 d
(3.0819 ± 0.0246 y)
Argument of
(ω) 235.4 ± 10.6°
Time of periastron (T0) 2452466.7 ± 3.2 JD
Physical characteristics
Minimum mass (m sin i) 9.76 ± 2.15 MJ
Discovery information
Discovery date March 20, 2009
Discoverer(s) Doellinger et al.
Detection method radial velocity
Discovery site TLS
Discovery status Published
Other designations
HIP 76311 b, HR 5811 b
Database references
Extrasolar Planets

HD 139357 b is an extrasolar planet located approximately 396 light years away in the constellation of Draco, orbiting the 6th magnitude K-type giant star HD 139357. It has a minimum mass very massive, at nearly 10 times that of Jupiter, but its radius is unknown (probably no more than 1.2 Jupiters). This planet is probably most likely be a brown dwarf if true mass were to be known. The reason why true mass is unknown is due to its unknown inclination. Follow up observations via direct imaging may determine its radius, hence density and surface gravity, and inclination to allow it to determine whether this object actually be a brown dwarf or a supermassive planet. As it is typical for supermassive planets, this orbits further from stars than Earth is from the Sun. The planet’s year is over three Earth years. However, the orbital eccentricity of this planet is much greater than Earth, 0.1 vs 0.017. Like most known extrasolar planets, it was detected by a wobble method, which finds planet by studying wobbling motion of a star in circular motion caused by gravity of planets as they orbit the star. This detection took place on March 20, 2009, which was the first day of spring.

See also


  • Doellinger et al. (2009). Planetary companion candidates around the K giant stars 42 Draconis and HD 139357. . Astronomy & Astrophysics. arΧiv:0903.3593.  

Coordinates: Sky map 15h 35m 16.1992s, +53° 55′ 19.717″



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