Confirmed exoplanet · Database record + computed analysis
GJ 3942 b
A confirmed world orbiting GJ 3942, 55.2 light-years away.
A sub-Neptune
2.57 Earth radii, likely a rocky core under a thick gas or steam envelope rather than a walkable surface.
The orbit
Its year, one full orbit, takes just 6.9 Earth days. Orbiting this tightly around a cool star, it is very likely tidally locked: one hemisphere in permanent day, the other in permanent night.
Temperature and starlight
Its equilibrium temperature (the airless-world estimate) is about 317 °C. Above water's boiling point. It receives 20.5 times the starlight Earth gets.
Its sun
Its star is a red dwarf (3,867 K surface), type M0: small, dim, flare-prone, and destined to outlive the Sun many times over.
How far is that, really?
At 55 light-years, tonight's light from this system left it around the year 1970. A Voyager-speed probe would need roughly 976,879 years to get there.
How we found it
It was found by the radial-velocity method: the planet's gravity swings its star in a small circle, and that wobble shows up as a rhythmic Doppler shift in the starlight. The wobble's size gives the planet's minimum mass. The discovery was announced in 2017 from Roque de los Muchachos Observatory.
Everything above is computed from the archive’s measured values for this planet. Where a quantity is missing, the statement is omitted rather than guessed.
About this record
The measured values come from the NASA Exoplanet Archive, and any missing value has not been determined yet; the Atlas never fills gaps with guesses. More standout worlds: Proxima b, TRAPPIST-1e, K2-18 b, 55 Cancri e, and the detection methods that found them all.