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HD 139357 b
Extrasolar planet List of extrasolar planets
Parent star

<tr> <td colspan="2">Star</td> <td>HD 139357</td></tr><tr> <td colspan="2">Constellation</td> <td>Draco</td></tr><tr> <td>Right ascension</td> <td style="text-align: center">(α)</td> <td>15h 35m 16.20s[1]</td></tr><tr> <td>Declination</td> <td style="text-align: center">(δ)</td> <td>+53° 55′ 19.7″[1]</td></tr><tr> <td>Apparent magnitude</td> <td style="text-align: center">(mV)</td> <td>5.977</td></tr><tr><td colspan="2">Distance</td><td>390 ± 10[1] ly
(118 ± 4[1] pc)</td></tr><tr><td colspan="2">Spectral type</td> <td>K4III</td></tr>

Orbital elements

<tr><td>Semimajor axis</td><td style="text-align: center">(a)</td> <td>2.36 ± 0.2 AU</td></tr><tr> <td>Periastron</td> <td style="text-align: center">(q)</td> <td>2.12 AU</td></tr><tr> <td>Apastron</td> <td style="text-align: center">(Q)</td> <td>2.60 AU</td></tr><tr> <td>Eccentricity</td> <td style="text-align: center">(e)</td> <td>0.1 ± 0.02</td></tr><tr><td>Orbital period</td><td style="text-align: center">(P)</td> <td>1125.7 ± 9 d
(3.0819 ± 0.0246 y)</td></tr><tr> <td>Argument of
periastron
</td> <td style="text-align: center">(ω)</td> <td>235.4 ± 10.6°</td></tr><tr> <td>Time of periastron</td> <td style="text-align: center">(T0)</td> <td>2452466.7 ± 3.2 JD</td></tr>

Physical characteristics

<tr><td>Minimum mass</td><td style="text-align: center">(m sin i)</td><td>9.76 ± 2.15 MJ</td></tr>

Discovery information

<tr> <td colspan="2">Discovery date</td> <td>March 20, 2009</td></tr><tr> <td colspan="2">Discoverer(s)</td> <td>Doellinger et al.[2]</td></tr><tr> <td colspan="2">Discovery method</td> <td>radial velocity</td></tr><tr> <td colspan="2">Discovery site</td> <td>TLS</td></tr><tr> <td colspan="2">Discovery status</td> <td>Published</td></tr>

Other designations
HIP 76311 b, HR 5811 b

<tr style="background-color: #A0B0FF;"><td align=center colspan=3>Database references</td></tr><tr valign=baseline><td colspan=2>Extrasolar Planets
Encyclopaedia
</td><td>data</td></tr><tr><td colspan=2>SIMBAD</td><td>data</td></tr>

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 Edit

References Edit

  1. 1.0 1.1 1.2 1.3 (2007). Validation of the new Hipparcos reduction. Astronomy and Astrophysics 474 (2): 653–664. Vizier catalog entry
  2. (2009). Planetary companion candidates around the K giant stars 42 Draconis and HD 139 357. Astronomy and Astrophysics 499 (3): 935–942.

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


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