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 2019, by radial velocity (NASA Exoplanet Archive).
Its planets
HD 31527 d — 3.5 times Earth's width (estimated from its mass, not measured), a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 270 days; about 54 °C, between freezing and boiling; found in 2019 by radial velocity.
HD 31527 b — 3.2 times Earth's width (estimated from its mass, not measured), a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 17 days; about 560 °C, hotter than boiling water; found in 2019 by radial velocity.
HD 31527 c — 3.9 times Earth's width (estimated from its mass, not measured), a 'sub-Neptune' — bigger than Earth, smaller than Neptune; its year lasts 51 days; about 300 °C, hotter than boiling water; found in 2019 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.