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.

[7] 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.

The discoverers of HD 40307 g did not try to refute Barnes, on the nature of b and its extrapolation to the other planets.

[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.