# HD 139357 b

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Extrasolar planet in the constellation Draco

HD 139357 b Discovery Discovered by Doellinger et al.[1] Discovery site TLS Discovery date March 20, 2009 Detection method radial velocity Orbital characteristics Apastron 2.60 AU (389,000,000 km) 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 [extrasolar planet](/source/Extrasolar_planet) or [brown dwarf](/source/Brown_dwarf) located approximately 390 [light years](/source/Light_year) away, orbiting the 6th [magnitude](/source/Apparent_magnitude) [K-type](/source/K-type_star) [giant](/source/Giant_star) [star](/source/Star) [HD 139357](/source/HD_139357) in the [constellation](/source/Constellation) of [Draco](/source/Draco_(constellation)). 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 [minimum mass](/source/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](/source/Brown_dwarf) rather than a planet. The reason why the object's [true mass](/source/True_mass) was initially unknown is due to the undetermined [inclination](/source/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 MJ via [astrometry](/source/Astrometry), although this estimate is poorly constrained. If this is the true mass, the object would be a [brown dwarf](/source/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 [orbital eccentricity](/source/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](/source/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](/source/42_Draconis_b)

- [Iota Draconis b](/source/Iota_Draconis_b)

## References

1. **[^](#cite_ref-Döllinger2009_1-0)** Döllinger, M. P.; et al. (2009). ["Planetary companion candidates around the K giant stars 42 Draconis and HD 139 357"](http://www.aanda.org/articles/aa/full_html/2009/21/aa10837-08/aa10837-08.html). *Astronomy and Astrophysics*. **499** (3): 935–942. [arXiv](/source/ArXiv_(identifier)):[0903.3593](https://arxiv.org/abs/0903.3593). [Bibcode](/source/Bibcode_(identifier)):[2009A&A...499..935D](https://ui.adsabs.harvard.edu/abs/2009A&A...499..935D). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/200810837](https://doi.org/10.1051%2F0004-6361%2F200810837). [S2CID](/source/S2CID_(identifier)) [15677079](https://api.semanticscholar.org/CorpusID:15677079).

1. **[^](#cite_ref-Feng2022_2-0)** Feng, Fabo; Butler, R. Paul; et al. (August 2022). ["3D Selection of 167 Substellar Companions to Nearby Stars"](https://doi.org/10.3847%2F1538-4365%2Fac7e57). *[The Astrophysical Journal Supplement Series](/source/The_Astrophysical_Journal_Supplement_Series)*. **262** (21): 21. [arXiv](/source/ArXiv_(identifier)):[2208.12720](https://arxiv.org/abs/2208.12720). [Bibcode](/source/Bibcode_(identifier)):[2022ApJS..262...21F](https://ui.adsabs.harvard.edu/abs/2022ApJS..262...21F). [doi](/source/Doi_(identifier)):[10.3847/1538-4365/ac7e57](https://doi.org/10.3847%2F1538-4365%2Fac7e57). [S2CID](/source/S2CID_(identifier)) [251864022](https://api.semanticscholar.org/CorpusID:251864022).

v t e Constellation of Draco List of stars in Draco Draco in Chinese astronomy Stars Bayer α (Thuban) β (Rastaban) γ (Eltanin) δ (Altais) ε (Tyl) ζ (Aldhibah) η (Athebyne) θ ι (Edasich) κ λ (Giausar) μ (Alrakis) ν (Kuma) ξ (Grumium) ο π ρ σ (Alsafi) τ υ φ χ ψ1 (Dziban) ψ2 ω Flamsteed 4 6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 50 59 64 (e) 68 Variable TW YY AG BY CL CM CX DO EK HP V581 HR 3751 4126 4934 5811 6237 6518 6618 (Alruba) 6817 7137 7783 HD 109246 (Funi) 101364 128717 147379 156279 158259 176693 191939 Other 2MASS 1237+6526 2MASS J17554042+6551277 G 240-72 GD 356 Gliese 420 Gliese 625 Gliese 687 GRW +70 8247 Kepler-4 Kepler-10 Kepler-12 Kepler-90 Kepler-296 KOI-256 LP 71-82 Qatar-1 SDSS J1240+6710 Struve 2398 TOI-1136 WD 1856+534 WISE 1647+5632 WISE 1841+7000 Exoplanets HD 139357 b HD 167042 b ι Dra b (Hypatia) Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i Kepler-296b c d e f TOI-1452 b TrES-2b Star clusters LAMOST 1 Nebulae Cat's Eye Nebula NGC 6742 Galaxies NGC 3147 3197 3735 4121 4125 4221 4236 4319 4331 4332 4363 4441 4513 4545 4589 5678 5777 5866 5866B 5879 5905 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6338 6340 6365 6373 6394 6412 6503 6505 6566 6621 6622 6670 6676 6786 6789 Other 1ES 1927+654 1ES 1959+650 3C 249.1 3C 305 3C 319 3C 343 3C 343.1 3C 351 3C 356 3C 371 3C 380 3C 390.3 3C 401 4C +72.26 4C 73.08 8C 1241+735 Abell 2218 BCG Bean galaxy Beaver galaxy BZQ J1727+5510 Draco Dwarf Draco II GB 1508+5714 Goldfish galaxy H1821+643 HFLS3 IERS B1946+708 IRAS F17179+5444 IRAS 18580+6527 J120011.1+680924.8 KKR 25 Markarian 817 Markarian 876 Original TRG PGC 39058 Porphyrion QSO B1823+568 RGZ J172749.5+534647 S5 1803+784 S5 2007+777 SDSS J1715+6008 Tadpole Galaxy UGC 9391 UGC 9405 UGC 11241 UGC 11411 WISEA J145223.62+611707.5 WN B1851+5707 Galaxy clusters Abell 2218 CL1358+62 Draco Supercluster NGC 5866 Group Astronomical events SN 2003jb SN 2005B SN 2016aps Swift J1644+57 Category

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Adapted from the Wikipedia article [HD 139357 b](https://en.wikipedia.org/wiki/HD_139357_b) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HD_139357_b?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.