The planet was discovered by the radial velocity method, using the European Southern Observatory's HARPS apparatus, in June 2008.
As with many other extrasolar planets, HD 40307 b was discovered by measuring variations in the radial velocity of the star it orbits.
These measurements were made by the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph at the Chile-based La Silla Observatory.
This supports a hypothesis concerning the possibility that the metallicity of stars during their births may determine whether a protostar's accretion disk forms gas giants or terrestrial planets.
[2] The Arizonan astronomer Rory Barnes's mathematical model, in 2009, found that "Planet b's orbit must be more than 15◦ from face-on";[6] however it cannot be much more.