# HD 128311 c

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Exoplanet in the constellation Boötes

HD 128311 c Discovery Discovered by Vogt et al. Discovery site California, United States Discovery date June 24, 2005 Detection method Doppler spectroscopy Orbital characteristics[1] Apastron 2.02 AU (302,000,000 km) Periastron 1.46 AU (218,000,000 km) Semi-major axis 1.740 ± 0.010 AU (260,300,000 ± 1,500,000 km) Eccentricity 0.159±0.006 Orbital period (sidereal) 921.538 ± 1.15 d (2.52303 ± 0.00315 a) Average orbital speed 20.7 Inclination 55.950±14.553 Longitude of ascending node 229.392±14.473 Time of periastron 2449565.615±18.01 Argument of periastron 15.445±6.87 Semi-amplitude 74.799±1.497 Star HD 128311 Physical characteristics[1] Mass 3.789+0.924 −0.432 MJ

**HD 128311 c** is an [exoplanet](/source/Exoplanet) located approximately 54 [light-years](/source/Light-year) away in the [constellation](/source/Constellation) of [Boötes](/source/Bo%C3%B6tes_(constellation)). This planet orbits in an eccentric orbit at 1.74 [AU](/source/Astronomical_unit) from its [star](/source/Star) ([HD 128311](/source/HD_128311)). The planet has a [minimum mass](/source/Minimum_mass) of 3.22 [MJ](/source/Jupiter_mass),[2] and [astrometric](/source/Astrometry) observations in 2014 revealed its true mass to be 3.789 [MJ](/source/Jupiter_mass).[1]

## References

1. ^ [***a***](#cite_ref-McArthur2014_1-0) [***b***](#cite_ref-McArthur2014_1-1) [***c***](#cite_ref-McArthur2014_1-2) McArthur, Barbara E.; et al. (2014). ["Astrometry, Radial Velocity, and Photometry: The HD 128311 System Remixed with Data from HST, HET, and APT"](https://doi.org/10.1088%2F0004-637X%2F795%2F1%2F41). *[The Astrophysical Journal](/source/The_Astrophysical_Journal)*. **795** (1): 41. [Bibcode](/source/Bibcode_(identifier)):[2014ApJ...795...41M](https://ui.adsabs.harvard.edu/abs/2014ApJ...795...41M). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/795/1/41](https://doi.org/10.1088%2F0004-637X%2F795%2F1%2F41). [hdl](/source/Hdl_(identifier)):[2152/35199](https://hdl.handle.net/2152%2F35199). [S2CID](/source/S2CID_(identifier)) [122980723](https://api.semanticscholar.org/CorpusID:122980723).

1. **[^](#cite_ref-Vogt2005_2-0)** Vogt, Steven S.; et al. (2005). ["Five New Multicomponent Planetary Systems"](https://authors.library.caltech.edu/36250/1/0004-637X_632_1_638.pdf) (PDF). *The Astrophysical Journal*. **632** (1): 638–658. [Bibcode](/source/Bibcode_(identifier)):[2005ApJ...632..638V](https://ui.adsabs.harvard.edu/abs/2005ApJ...632..638V). [doi](/source/Doi_(identifier)):[10.1086/432901](https://doi.org/10.1086%2F432901). [S2CID](/source/S2CID_(identifier)) [16509245](https://api.semanticscholar.org/CorpusID:16509245).

## External links

- ["Notes for planet HD 128311 c"](https://exoplanet.eu/catalog/hd_128311_c--266/). *[Extrasolar Planets Encyclopaedia](/source/Extrasolar_Planets_Encyclopaedia)*. Retrieved 2008-08-18.

- ["HD 128311"](https://web.archive.org/web/20080514224054/http://media4.obspm.fr/exoplanets/base/etoile.php?nom=HD+128311). *Exoplanets*. Archived from [the original](http://media4.obspm.fr/exoplanets/base/etoile.php?nom=HD+128311) on 2008-05-14. Retrieved 2008-08-18.

v t e HD 128311 System Stars HD 128311 Planets HD 128311 b HD 128311 c

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