HIP 79431 b

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HIP 79431 b
Exoplanet List of exoplanets
Parent star
Star HIP 79431
Constellation Scorpius
Right ascension (α) 16h 12m 41.77s
Declination (δ) –18° 52′ 31.8″
Apparent magnitude (mV) 11.337
Distance 47.0 ± 2.2 ly
(14.4 ± 0.7 pc)
Spectral type M3V
Mass (m) 0.49 ± 0.05 M
Temperature (T) 3191 ± 100 K
Metallicity [Fe/H] 0.4 ± 0.1
Orbital elements
Semi-major axis (a) 0.36 AU
(54 Gm)
Periastron (q) 0.25 AU
(38 Gm)
Apastron (Q) 0.46 AU
(69 Gm)
Eccentricity (e) 0.29
Orbital period (P) 111.7 ± 0.7 d
(0.306 y)
Orbital speed (υ) 35 km/s
Argument of
(ω) 287.4 ± 3.2°
Time of periastron (T0) 2454980.3 ± 1.2 JD
Physical characteristics
Minimum mass (m sin i) 2.1 MJ
Discovery information
Discovery date January 7, 2010
Discoverer(s) Apps et al.
Discovery method Doppler spectroscopy
Discovery site Keck Observatory
Discovery status Published
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

HIP 79431 b is an extrasolar planet discovered by the W. M. Keck Observatory in 2010. The planet is found in an M type dwarf star catalogued as HIP 79431 and is located within the Scorpius constellation approximately 47 light years away from the Earth. Its orbital period lasts about 111.7 days and has an orbital eccentricity of 0.29. The planet is the 6th giant planet to be detected in the Doppler surveys of M dwarfs and is considered to be one of the most massive planets found around M dwarf stars.[1][2][3][4]


HIP 79431 b is located in orbit around a star whose metallicity had been challenging to be assessed due to the uncertainties within the molecular data line however it has not been typical for M Dwarfs to have strong emissions from the core data lines. This led to the inclusion of the HIP 79431 star to the KECK program in April 2009 as part of the exoplanet studies for low mass stars. During this study, 13 Doppler measurements of the star were done over a 6-month period using the High Resolution Echelle Spectrometer (HIRES). The exposure times used in its observation was 600 seconds which yielded a signal-to-noise ratio of just under 100. Each program observation required the use of iodine absorption lines in order to model the wavelength scale as well as the instrumental profile of the telescope and spectrometer optics. The Doppler experiments derived radial velocities fit the Keplerian model showing an unambiguous signal and orbital parameters which best fit planetary gravitational pull, this revealed the presence of the planet HIP 79431 b. However, there is no evidence that any additional planets was found.[5][6][7]

Low transit possibility[edit]

The planet HIP 79431 b has a low transit probability mainly due to its semi-major axis orientation. Another observation with regard to its eccentricity orbit is that it brings the planet closer to its star periastron increasing the probability of a transit, which was estimated as a meager 0.5%. According to the KECK program, if a transit would occur, the depth would be remarkable mainly due to the calculated mass of the planet.[8]

See also[edit]


  1. ^ "M Dwarf Planets". Deep Fly. Retrieved 2010-02-09. 
  2. ^ "Planet : HIP 79431 b". Exo Planet.eu. Retrieved 2010-02-09. 
  3. ^ Kevin Apps; Clubb; Fischer; Eric Gaidos; Howard; Johnson; Marcy; Howard Isaacson; Giguere (2010). "M2K A Jovian Mass Planet around M3V star HIP 79431". arXiv:1001.1174free to read [astro-ph.EP]. 
  4. ^ "Estrella: HIP 79431". NASA. Retrieved 2010-02-09. 
  5. ^ "M2K: I. A Jupiter-Mass Planet Orbiting the M3V Star HIP 79431". Publications of the Astronomical Society of the Pacific, 122:156–161. arXiv:1001.1174free to read. Bibcode:2010PASP..122..156A. doi:10.1086/651058. 
  6. ^ Kevin Apps; Clubb; Fischer; Eric Gaidos; Howard; Johnson; Marcy; Howard Isaacson; Giguere (2010). "Addition to the KECK Program of HIP 79431". arXiv:1001.1174free to read [astro-ph.EP]. 
  7. ^ M. B. N. Kouwenhoven; A. G. A. Brown; L. Kaper (2007). "A brown dwarf desert for intermediate mass stars in Scorpius OB2?". Astronomy and Astrophysics. 464: 581–599. arXiv:astro-ph/0611903free to read. Bibcode:2007A&A...464..581K. doi:10.1051/0004-6361:20054396. 
  8. ^ Kevin Apps; Clubb; Fischer; Eric Gaidos; Howard; Johnson; Marcy; Howard Isaacson; Giguere (2010). "Transit Ephemeris". arXiv:1001.1174free to read [astro-ph.EP].