Voyager 1 at the speed it moved outward over the year to 2026-10-25 (JPL Horizons). Driving: nonstop, never refuelling.
How it was found
First planet found in 2011, by transit (NASA Exoplanet Archive).
Its planets
Kepler-31 c — 5.3 times Earth's width, Neptune-sized; its year lasts 43 days; about 340 °C, hotter than boiling water; found in 2011 by transit.
Kepler-31 d — 3.9 times Earth's width, a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 88 days; about 210 °C, hotter than boiling water; found in 2014 by transit.
Kepler-31 b — 5.5 times Earth's width, Neptune-sized; its year lasts 21 days; about 510 °C, hotter than boiling water; found in 2011 by transit.
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.