HD 139357 b

HD 139357 b

Exoplanet		List of exoplanets
Parent star
Star		HD 139357
Constellation		Draco
Right ascension	(α)	15^h 35^m 16.20^s[1]
Declination	(δ)	+53° 55′ 19.7″[1]
Apparent magnitude	(mV)	5.977
Distance		390 ± 10[1] ly (118 ± 4[1] pc)
Spectral type		K4III
Orbital elements
Semi-major 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 periastron	(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.[2]
Discovery method		radial velocity
Discovery site		TLS
Discovery status		Published
Other designations
HIP 76311 b, HR 5811 b
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		data
Exoplanet Archive		data
Open Exoplanet Catalogue		data

HD 139357 b is a very massive extrasolar planet or brown dwarf located approximately 390 light years away, orbiting the 6th magnitude K-type giant star HD 139357 in the constellation of Draco. The detection occurred on March 20, 2009, which was the first day of spring.

The actual mass and radius of this body remain known, but it has a minimum mass of nearly 10 times that of Jupiter and a radius of probably no more than 1.2 times Jupiter's. Most likely this is a brown dwarf rather than a planet. The reason why the object's true mass is unknown is due to the undetermined inclination of its orbital plane. Follow up observations via direct imaging may determine its radius and orbital inclination, thereby giving its density and surface gravity, which will allow a determination as to whether this object is a brown dwarf or a supermassive planet.

As it is typical for supermassive planets, this orbits further from its host star than Earth is from the Sun. The planet’s year is over three Earth years. However, the orbital eccentricity of this object is much greater than Earth's: 0.1 vs. 0.017. Like most known extrasolar planets, it was detected by the wobble method, which detects planets through the circular wobbling motion of the star caused by the gravity of orbiting body.

See also

• 42 Draconis b
• Iota Draconis b

References

1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
2. Döllinger, M. P.; et al. (2009). "Planetary companion candidates around the K giant stars 42 Draconis and HD 139 357". Astronomy and Astrophysics 499 (3): 935–942. arXiv:0903.3593. Bibcode:2009A&A...499..935D. doi:10.1051/0004-6361/200810837.

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