HD 40307 B - Orbit and Mass

Orbit and Mass

HD 40307 b is the second lightest planet discovered in the system, with at least 4.2 times the mass of the Earth. The planet orbits the star HD 40307 every 4.3 Earth days, corresponding of its location at approximately 0.047 astronomical units from the star. The eccentricity of the planet's orbit was found to not differ significantly from zero, meaning that there is insufficient data to distinguish the orbit from an entirely circular one.

The star around which HD 40307 b orbits has a low metallicity, compared to other planet-bearing stars. 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.

The Arizonan astronomer Rory Barnes's mathematical model, in 2009, found that "Planet b’s orbit must be more than 15◦ from face-on"; however it cannot be much more.

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