HD 40307 g
Approximate size comparison of HD 40307 g with Earth.
Discovery
Discovered byMikko Tuomi et al.
Discovery siteLa Silla Observatory, Chile
Discovery dateOctober 28, 2012
radial velocity, using HARPS
Orbital characteristics
0.600 AU (89,800,000 km)
Eccentricity0.22[1]
197.8 ± 9.0[1] d
Semi-amplitude0.95 ± 0.3[1]
StarHD 40307
Physical characteristics
Mean radius
2.39[2] R🜨
Mass7.09[2] ME
Temperature277.6[3]
NASA Exoplanet Exploration Program "travel poster" for HD 40307 g

HD 40307 g is an exoplanet candidate suspected to be 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[1][4][5] by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Göttingen, Germany.[6]

The existence of the planet was disputed in 2015, as more Doppler spectroscopy data has become available.[7]

Planetary characteristics

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."[4]

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,[8] 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.[9] 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."[4]

See also

References

  1. ^ a b c d Tuomi, Mikko; Anglada-Escudé, Guillem; Gerlach, Enrico; Jones, Hugh R. A.; Reiners, Ansgar; Rivera, Eugenio J.; Vogt, Steven S.; Butler, R. Paul (17 December 2012). "Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307". Astronomy & Astrophysics. 549: A48. arXiv:1211.1617. Bibcode:2013A&A...549A..48T. doi:10.1051/0004-6361/201220268. S2CID 7424216.
  2. ^ a b "PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo". Archived from the original on 2019-05-21. Retrieved 2014-01-09.
  3. ^ "HEC: Data of Potential Habitable Worlds". University of Puerto Rico at Arecibo (Planetary Habitability Laboratory). November 12, 2012. Archived from the original on December 1, 2017. Retrieved November 16, 2012.
  4. ^ a b c Wall, Mike (November 7, 2012). "'Super-Earth' Alien Planet May Be Habitable for Life". Space.com. Retrieved November 8, 2012.
  5. ^ Tate, Karl (November 7, 2012). "Super-Earth Planet: Potentially Habitable Alien World Explained (Infographic)". Space.com. Retrieved November 8, 2012.
  6. ^ Murrin, Marc (November 8, 2012). "Astronomers discover a potentially habitable Super-Earth HD 40307g (Infographic)". tech-stew.com. Archived from the original on November 10, 2012. Retrieved November 8, 2012.
  7. ^ Díaz, R. F.; et al. (2016). "The HARPS search for southern extra-solar planets. XXXVIII. Bayesian re-analysis of three systems. New super-Earths, unconfirmed signals, and magnetic cycles". Astronomy and Astrophysics. 585. A134. arXiv:1510.06446. Bibcode:2016A&A...585A.134D. doi:10.1051/0004-6361/201526729. S2CID 118531921.
  8. ^ 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. S2CID 18849636.
  9. ^ 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". USA Today.

External links


HD 40307 system
2012 in space
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