K2-198 d
K2-198 d is a mini-Neptune orbiting K2-198 in the constellation Virgo. It lies about 361 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is K2-198 d?
K2-198 d has a radius of 2.44 times that of Earth.
Is K2-198 d in the Habitable Zone?
The position of K2-198 d relative to the habitable zone of K2-198 cannot be precisely determined from the available orbital data.
Habitable zone of K2-198: 0.478–1.145 AU (conservative: 0.605–1.086 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on K2-198 d
The equilibrium temperature of K2-198 d is about 943 K (670 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on K2-198 d — one full orbit around K2-198 — lasts 7.45 Earth days, shorter than Mercury's 88-day year.
How Was K2-198 d Discovered?
K2-198 d was discovered in 2019 using the transit method, with observations from K2.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is K2-198 d?
K2-198 d is 360.6 light-years (110.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1666. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,346,560 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. K2-198 d scores 0.25, ranking #3,122 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-198
K2-198
- Surface temperature
- 5,213 K (Sun: 5,772 K)
- Mass
- 0.80 M☉
- Radius
- 0.76 R☉
The K2-198 Planetary System
K2-198 d is one of 3 known planets in the K2-198 system. Its siblings:
K2-198 d — Complete Data
| Radius | 2.438 Earth radii (0.218 Jupiter radii) |
|---|---|
| Orbital period | 7.45 days |
| Equilibrium temperature | 943 K (670 °C) |
| Earth Similarity Index | 0.25 |
| Distance from Earth | 360.6 light-years (110.6 parsecs) |
| Constellation | Virgo |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-08-09. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-198 d
Is K2-198 d habitable?
K2-198 d is not known to orbit within the habitable zone of K2-198, and as a mini-Neptune it is an unlikely candidate for life as we know it.
How far away is K2-198 d?
K2-198 d is about 361 light-years from Earth in the constellation Virgo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,346,560 years to get there.
How big is K2-198 d compared to Earth?
K2-198 d has 2.44 times the radius of Earth.
How long is a year on K2-198 d?
One orbit around K2-198 takes 7.5 Earth days — short enough that 49 of its years would fit into one Earth year.
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