Voyager 1 at the speed it moved outward over the year to 2026-10-25 (JPL Horizons). Driving: nonstop, never refuelling.
Facts
HD 40307 g has an equilibrium temperature between −50 and +50 °C.
How it was found
First planet found in 2009, by radial velocity (NASA Exoplanet Archive).
Its planets
HD 40307 f — 2.1 times Earth's width (estimated from its mass, not measured), a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 52 days; about 130 °C, hotter than boiling water; found in 2013 by radial velocity.
HD 40307 d — about 1,800 times Earth's mass; its year lasts 20 days; about 270 °C, hotter than boiling water; found in 2009 by radial velocity.
HD 40307 g — 2.6 times Earth's width (estimated from its mass, not measured), a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 200 days; about −18 °C, below freezing; found in 2013 by radial velocity.
HD 40307 b — about 1,200 times Earth's mass; its year lasts 4 days; about 640 °C, hotter than boiling water; found in 2009 by radial velocity.
HD 40307 c — about 1,900 times Earth's mass; its year lasts 10 days; about 420 °C, hotter than boiling water; found in 2009 by radial velocity.
NASA Exoplanet Archive, Planetary Systems Composite Parameters (fetched 2026-11-02). Composite values: where a planet's size or mass was not measured, the archive estimates it from the other.
This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.