HD 139357 b

Extrasolar planet in the constellation Draco

Periastron

2.12 AU (317,000,000 km)
Semi-major axis	2.36 ± 0.2 AU (353,000,000 ± 30,000,000 km)
Eccentricity	0.1 ± 0.02
Orbital period (sidereal)	1125.7 ± 9 d 3.0819 ± 0.0246 y
Time of periastron	2452466.7 ± 3.2
Argument of periastron	235.4 ± 10.6
Star	HD 139357

HD 139357 b is a very massive

. The detection occurred on March 20, 2009, which was the first day of spring.

The actual mass and radius of this body remain uncertain, but it has a

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.

A 2022 study estimated the true mass of HD 139357 b at about 16.38 M_J via astrometry, although this estimate is poorly constrained. If this is the true mass, the object would be a brown dwarf.^[2]

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

, 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

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