Characteristics
HD 40307 b does not transit and has not been imaged. More specific characteristics, such as its radius, composition, and possible surface temperature cannot be determined.
With a lower mass bound of 4.2 times the mass of the Earth, HD 40307 b is presumably too small to be a jovian planet. This concept was challenged in a 2009 study, which stated that if HD 40307 b is terrestrial, the planet would be highly unstable and would be affected by tidal heating in a manner greater than Io, a volcanic satellite of planet Jupiter; restrictions that seem to bind terrestrial planets, however, do not restrict ice giant planets like Neptune or Uranus.
As strong tidal forces often result in the destruction of larger natural satellites in planets orbiting close to a star, it is unlikely that HD 40307 b hosts any satellites.
HD 40307 b, c, and d are presumed to have migrated in to their present orbits.
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