Voyager 1 at the speed it moved outward over the year to 2026-10-25 (JPL Horizons). Driving: nonstop, never refuelling.
Facts
K2-3 d has an equilibrium temperature between −50 and +50 °C.
How it was found
First planet found in 2015, by transit (NASA Exoplanet Archive).
Its planets
K2-3 b — 2.1 times Earth's width, a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 10 days; about 230 °C, hotter than boiling water; found in 2015 by transit.
K2-3 c — 1.6 times Earth's width, about Earth-sized — probably rocky; its year lasts 25 days; about 99 °C, between freezing and boiling; found in 2015 by transit.
K2-3 d — 1.5 times Earth's width, about Earth-sized — probably rocky; its year lasts 45 days; about 32 °C, between freezing and boiling; found in 2015 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.