Exoplanet · mini-Neptune
GJ 3998 d
GJ 3998 d is a mini-Neptune orbiting the star GJ 3998. Its year lasts 41.8 Earth days. It was discovered in 2025 by the Radial Velocity method.
| Host star | GJ 3998 |
|---|---|
| Distance | 59.2 light-years (18.1 pc) |
| Orbital period | 41.8 days |
| Orbital radius | 0.189 AU |
| Eccentricity | 0.000 |
| Radius | 2.34 R⊕ · 0.209 R♃ |
| Mass (minimum) | 6.07 M⊕ · 0.0191 M♃ |
| Density | 2.6 g/cm³ |
| Equilibrium temperature | 292 K (19 °C) |
| Stellar flux received | 1.2 × Earth |
| Discovery method | Radial Velocity |
| Discovery year | 2025 |
| Discovered by | Multiple Observatories |
Habitable zone
At the edge of the habitable zone (within the optimistic limits): liquid water would be possible only with a favourable atmosphere.
Its star in the sky
In the planet's sky its star is a disc 1.4° across: 2.6 times the Sun as we see it from Earth.
In the sky
A telescope is needed to see it: its apparent magnitude is 11.01. Visible from the whole Northern Hemisphere and south to latitude 79° S. North of latitude 79° N it never sets. It stands highest at midnight in June, the best time to observe it.
Light's journey
The light you see tonight set out around the year 1967. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 1.0 million years.
Planets in the same system
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.