Voyager 1 at the speed it moved outward over the year to 2026-10-25 (JPL Horizons). Driving: nonstop, never refuelling.
Facts
Kepler-68 d has an equilibrium temperature between −50 and +50 °C.
How it was found
First planet found in 2013, by transit and radial velocity (NASA Exoplanet Archive).
Its planets
Kepler-68 c — 1 times Earth's width, about Earth-sized — probably rocky; its year lasts 10 days; about 780 °C, hotter than boiling water; found in 2013 by transit.
Kepler-68 d — 14 times Earth's width (estimated from its mass, not measured), a giant, Jupiter-sized or more; its year lasts 630 days; about −12 °C, below freezing; found in 2013 by radial velocity.
Kepler-68 e — 11 times Earth's width (estimated from its mass, not measured), a giant, Jupiter-sized or more; its year lasts about 9 Earth years; about −130 °C, below freezing; found in 2023 by radial velocity.
Kepler-68 b — 2.4 times Earth's width, a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 5 days; about 1,000 °C, hot enough to melt rock; found in 2013 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.