HD 40307 g

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HD 40307 g
Exoplanet List of exoplanets
Parent star
Star HD 40307
Constellation Pictor
Right ascension (α) 05h 54m 04.2409s[1]
Declination (δ) −60° 01′ 24.498″[1]
Apparent magnitude (mV) 7.17[1]
Distance41.8 ± 0.3 ly
(12.83 ± 0.09[1] pc)
Spectral type K2.5V[1]
Radius (r) 0.716 ± 0.010[2] R
Temperature (T) 4977 ± 59[3] K
Metallicity [Fe/H] −0.31 ± 0.03[3]
Age 1.2 (≥ 0.2)[4] Gyr
Orbital elements
Semi-major axis(a) 0.600[5] AU
Eccentricity (e) 0.22[5]
Orbital period(P) 197.8 ± 9.0[5] d
Semi-amplitude (K) 0.95 ± 0.3[5] m/s
Physical characteristics
Mass(m)7.09[6] M
Radius(r)2.39 [6] R
Stellar flux(F)0.62,[7][8] 0.68[9]
Maximum stellar flux(F⊙max)1.03[8]
Minimum stellar flux(F⊙min)0.42[8]
Temperature (T) 277.6[citation needed][9]
Discovery information
Discovery date October 28, 2012
Discoverer(s) Mikko Tuomi et al.
Discovery method radial velocity, using HARPS
Discovery site La Silla Observatory, Chile
Discovery status Announced[5]
Database references
Extrasolar Planets
Exoplanet Archivedata
Open Exoplanet Cataloguedata

HD 40307 g is an exoplanet orbiting in the habitable zone of HD 40307. It is located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Observatory's HARPS apparatus[5][10][11] by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Goettingen, Germany.[12]

Composition theories[edit]

The codiscoverer Hugh Jones, of the University of Hertfordshire in England, surmised: "The longer orbit of the new planet means that its climate and atmosphere may be just right to support life." [10]

However, another astronomer, Rory Barnes of the University of Washington, had already studied the orbits of the planets b, c, and d. First, Barnes had presumed b to take on too much tidal heating for it to be terrestrial, instead predicting a "mini-Neptune". He thought that b, c, and d had all migrated inward,[13] which extrapolates to e and f as well, which are further out, but not by much. It is possible that HD 40307 g has also migrated into where it is now. The discoverers of HD 40307 g did not try to refute Barnes, on the nature of b and its extrapolation to the other planets. The composition of g is unsettled.[14] Lead author Mikko Tuomi, also of the University of Hertfordshire, stated "If I had to guess, I would say 50-50 ... But the truth at the moment is that we simply do not know whether the planet is a large Earth or a small, warm Neptune without a solid surface."[10]

See also[edit]


  1. ^ a b c d e "HD 40307". SIMBAD. Centre de Données astronomiques de Strasbourg. 2008. Retrieved 18 June 2008.
  2. ^ HD 40307, entry, CDS database J/A+A/450/735; described in Effective temperature scale and bolometric corrections from 2MASS photometry, E. Masana, C. Jordi, and I. Ribas, Astronomy and Astrophysics 450, #2 (May 2006), pp. 735–746. Bibcode2006A&A...450..735M. doi:10.1051/0004-6361:20054021.
  3. ^ a b M. Mayor; S. Udry; C. Lovis; F. Pepe; D. Queloz; W. Benz; J.-L. Bertaux; F. Bouchy; C. Mordasini; D. Segransan (2009). "The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 Super-Earths (4.2, 6.9, & 9.2 Earth masses)". Astronomy and Astrophysics. 493 (2): 639–644. arXiv:0806.4587. Bibcode:2009A&A...493..639M. doi:10.1051/0004-6361:200810451.
  4. ^ HD 40307, database entry, Geneva-Copenhagen Survey of Solar neighbourhood, J. Holmberg et al., 2007, CDS database V/117A, accessed November 19, 2008; described in The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ~14 000 F and G dwarfs, B. Nordström, M. Mayor, J. Andersen, J. Holmberg, F. Pont, B. R. Jørgensen, E. H. Olsen, S. Udry, and N. Mowlavi, Astronomy and Astrophysics 418 (May 2004), pp. 989–1019, Bibcode2004A&A...418..989N, doi:10.1051/0004-6361:20035959.
  5. ^ a b c d e f Tuomi, Mikko; Anglada-Escude, Guillem; Gerlach, Enrico; Jones, Hugh R. R.; Reiners, Ansgar; Rivera, Eugenio J.; Vogt, Steven S.; Butler, R. Paul (2012). "Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307". Astronomy. 549: A48. arXiv:1211.1617. Bibcode:2013A&A...549A..48T. doi:10.1051/0004-6361/201220268.
  6. ^ a b PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo
  7. ^ Kopparapu, Ravi Kumar; Ramirez, Ramses; Kasting, James F; Eymet, Vincent; Robinson, Tyler D; Mahadevan, Suvrath; Terrien, Ryan C; Domagal-Goldman, Shawn; Meadows, Victoria; Deshpande, Rohit (2013). "Habitable Zones around Main-sequence Stars: New Estimates". The Astrophysical Journal. 765 (2): 131. arXiv:1301.6674. Bibcode:2013ApJ...765..131K. doi:10.1088/0004-637X/765/2/131.
  8. ^ a b c Brasser, R.; Ida, S.; Kokubo, E. (2014). "A dynamical study on the habitability of terrestrial exoplanets - II the super-Earth HD 40307 g". Monthly Notices of the Royal Astronomical Society. 440 (4): 3685. arXiv:1403.5868. Bibcode:2014MNRAS.440.3685B. doi:10.1093/mnras/stu555.
  9. ^ a b "HEC: Data of Potential Habitable Worlds". University of Puerto Rico at Arecibo (Planetary Habitability Laboratory). November 12, 2012.
  10. ^ a b c Wall, Mike (November 7, 2012). "'Super-Earth' Alien Planet May Be Habitable for Life". Space.com. Retrieved November 8, 2012.
  11. ^ Tate, Karl (November 7, 2012). "Super-Earth Planet: Potentially Habitable Alien World Explained (Infographic)". Space.com. Retrieved November 8, 2012.
  12. ^ Murrin, Marc (November 8, 2012). "Astronomers discover a potentially habitable Super-Earth HD 40307g (Infographic)". tech-stew.com. Retrieved November 8, 2012.
  13. ^ Barnes, R.; Jackson, B.; Raymond, S.; West, A.; Greenberg, R. (2009). "The HD 40307 Planetary System: Super-Earths or Mini-Neptunes?". The Astrophysical Journal. 695 (2): 1006–1011. arXiv:0901.1698. Bibcode:2009ApJ...695.1006B. doi:10.1088/0004-637X/695/2/1006.
  14. ^ University of Toronto astronomer Ray Jayawardhana, author of Strange New Worlds: The Search for Alien Planets and Life beyond Our Solar System. Paraphrased in Dan Vergano (November 7, 2012). "Habitable zone 'Super Earth' candidate planet detected".

External links[edit]

Coordinates: Sky map 05h 54m 04.2409s, −60° 01′ 24.498″