 Approximate size comparison of HD 40307 g withEarth. | |
| Discovery | |
|---|---|
| Discovered by | Mikko Tuomi et al. |
| Discovery site | La Silla Observatory,Chile |
| Discovery date | October 28, 2012 |
| radial velocity, usingHARPS | |
| 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 | |
| 2.39[2]R🜨 | |
| Mass | 7.09[2]ME |
| Temperature | 277.6[3] |
HD 40307 g is anexoplanet candidate suspected to be orbiting in thehabitable zone ofHD 40307. It is located 42light-years away in the direction of the southern constellationPictor. The planet was discovered by theradial velocity method, using theEuropean Southern Observatory'sHARPS apparatus[1][4][5] by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of theUniversity of Göttingen,Germany.[6]
The existence of the planet was disputed in 2015, as moreDoppler spectroscopy data has become available.[7]
The codiscoverer Hugh Jones, of theUniversity of Hertfordshire inEngland, 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]
2012 in space | ||
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Space probe launches |
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| Impact events | ||
| SelectedNEOs | ||
| Exoplanets |
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| Discoveries | ||
| Comets | ||
| Space exploration | ||
