Summary
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]
 Approximate size comparison of HD 40307 g with Earth. | |
| Discovery | |
|---|---|
| Discovered by | Mikko Tuomi et al. |
| Discovery site | La Silla Observatory, Chile |
| Discovery date | October 28, 2012 |
| radial velocity, using HARPS | |
| Orbital characteristics | |
| 0.600 AU (89,800,000 km) | |
| Eccentricity | 0.22[1] |
| 197.8 ± 9.0[1] d | |
| Semi-amplitude | 0.95 ± 0.3[1] |
| Star | HD 40307 |
| Physical characteristics | |
Mean radius | 2.39[2] R🜨 |
| Mass | 7.09[2] ME |
| Temperature | 277.6[3] |
The existence of the planet was disputed in 2015, as more Doppler spectroscopy data has become available.[7]
Planetary characteristics 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."[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 edit
References edit
- ^ 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.
- ^ a b "PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo". Archived from the original on 2019-05-21. Retrieved 2014-01-09.
- ^ "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.
- ^ a b c Wall, Mike (November 7, 2012). "'Super-Earth' Alien Planet May Be Habitable for Life". Space.com. Retrieved November 8, 2012.
- ^ Tate, Karl (November 7, 2012). "Super-Earth Planet: Potentially Habitable Alien World Explained (Infographic)". Space.com. Retrieved November 8, 2012.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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 edit
- "Super-Earth Discovered in Star's Habitable Zone". Exoplanets. 2017-05-10. Archived from the original on 2012-11-28. Retrieved 2012-11-08.