GJ 3998 d
GJ 3998 d is a super-Earth orbiting GJ 3998 in the constellation Ophiuchus. It lies about 59 light-years from Earth and was discovered in 2025 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is GJ 3998 d in the Habitable Zone?
GJ 3998 d orbits within the optimistic habitable zone of GJ 3998 — the broader region where liquid water might be possible under favorable atmospheric conditions.
Habitable zone of GJ 3998: 0.171–0.438 AU (conservative: 0.216–0.415 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 3998 d
GJ 3998 d receives 1.20 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 3998 d — one full orbit around GJ 3998 — lasts 41.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.189 AU — closer to its star than Mercury is to the Sun.
How Was GJ 3998 d Discovered?
GJ 3998 d was discovered in 2025 using the radial velocity method, with observations from Multiple Observatories.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is GJ 3998 d?
GJ 3998 d is 59.2 light-years (18.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1967. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,041,920 years to make the journey.
The Host Star: GJ 3998
GJ 3998
- Surface temperature
- 3,726 K (Sun: 5,772 K)
- Mass
- 0.52 M☉
- Radius
- 0.50 R☉
- Luminosity
- 0.0439 L☉
- Age
- 8.4 billion years (Sun: 4.6)
The GJ 3998 Planetary System
GJ 3998 d is one of 3 known planets in the GJ 3998 system. Its siblings:
GJ 3998 d — Complete Data
| Mass (best estimate) | 6.07 Earth masses |
|---|---|
| Orbital period | 41.78 days |
| Orbital distance | 0.189 AU |
| Stellar irradiation | 1.20× Earth |
| Distance from Earth | 59.2 light-years (18.1 parsecs) |
| Constellation | Ophiuchus |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-03-11. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 3998 d
Is GJ 3998 d habitable?
GJ 3998 d orbits within the habitable zone of GJ 3998, the region where liquid water could exist on a planet's surface. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is GJ 3998 d?
GJ 3998 d is about 59 light-years from Earth in the constellation Ophiuchus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,041,920 years to get there.
How long is a year on GJ 3998 d?
One orbit around GJ 3998 takes 41.8 Earth days.
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