HD 40307 g
| Exoplanet | List of exoplanets | |
|---|---|---|
| Parent star | ||
| Star | HD 40307 | |
| Constellation | Pictor | |
| Right ascension | (α) | 05h 54m 04.2409s |
| Declination | (δ) | −60° 01′ 24.498″ |
| Apparent magnitude | (mV) | 7.17 |
| Distance | 41.8 ± 0.3 ly (12.83 ± 0.09 pc) |
|
| Spectral type | K2.5V | |
| Radius | (r) | 0.716 ± 0.010 R☉ |
| Temperature | (T) | 4977 ± 59 K |
| Metallicity | [Fe/H] | −0.31 ± 0.03 |
| Age | 1.2 (≥ 0.2) Gyr | |
| Orbital elements | ||
| Semi-major axis | (a) | 0.600AU |
| Eccentricity | (e) | 0.22 |
| Orbital period | (P) | 197.8 ± 9.0d |
| Semi-amplitude | (K) | 0.95 ± 0.3m/s |
| Physical characteristics | ||
| Mass | (m) | 7.09M⊕ |
| Radius | (r) | 2.39 R⊕ |
| Stellar flux | (F⊙) | 0.62, 0.68⊕ |
| Maximum stellar flux | (F⊙max) | 1.03⊕ |
| Minimum stellar flux | (F⊙min) | 0.42⊕ |
| Temperature | (T) | 227.4 |
| 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 | |
| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
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 by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Goettingen, Germany.
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."
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, 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. 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."
Coordinates: 
05h 54m 04.2409s, −60° 01′ 24.498″
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