Planetary System
After spending five years observing the star, the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) announced that they had discovered three super-Earths in orbit around HD 40307 in June 2008. All three planets were detected by the radial velocity method, using the HARPS spectrograph system.
In 2012, an independent analysis carried out by a team of astronomers led by Mikko Tuomi of the University of Hertfordshire confirmed the existence of these planets and found an additional three planets in the systems.
Five of the planets orbit very close to the star, with the farthest of them located twice as close to HD 40307 than is the planet Mercury is to the Sun. The outermost planet orbits at a distance similar to the distance of Venus to the Sun and is situated well in the system's liquid water habitable zone.
The minimum masses of the planets in the system ranges from three to ten times the mass of the Earth, placing them somewhere between Earth and gas giants like Uranus and Neptune. Dynamical analysis of the innermost planets suggests that planet b is unstable at its age unless it is an ice giant, having migrated from further away. That implies similar for the other planets, even further out. The most recent discovery also indicates via dynamical analysis that the true planetary masses can not be much higher than their minimum masses.
| Companion |
Mass | Semimajor axis |
Orbital period |
Eccentricity | Radius |
|---|---|---|---|---|---|
| b | ≥ 4.0 +0.8 −0.7 M⊕ |
0.0468 +0.0023 −0.0024 |
4.3123 +0.0011 −0.0012 |
0.20 +0.16 −0.14 |
— |
| c | ≥ 6.6 +1.1 −1.0 M⊕ |
0.0799 ± 0.0040 | 9.6184 +0.0050 −0.0049 |
0.06 +0.06 −0.11 |
— |
| d | ≥ 9.5 +1.7 −1.5 M⊕ |
0.1321 +0.0066 −0.0064 |
20.432 +0.022 −0.024 |
0.07 +0.11 −0.07 |
— |
| e | ≥ 3.5 ± 1.4 M⊕ | 0.1886 +0.083 −0.0104 |
34.62 +0.21 −0.20 |
0.15 +0.13 −0.15 |
— |
| f | ≥ 5.2 +1.5 −1.6 M⊕ |
0.247 +0.011 −0.014 |
51.76 +0.50 −0.46 |
0.02 +0.20 −0.02 |
— |
| g | ≥ 7.1 ± 2.6 M⊕ | 0.600 +0.034 −0.033 |
197.8 +9.0 −5.7 |
0.29 +0.31 −0.29 |
— |
Read more about this topic: HD 40307
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