K2-401 b
K2-401 b is a mini-Neptune orbiting K2-401 in the constellation Sextans. It lies about 655 light-years from Earth and was discovered in 2022 using the transit method.
How Big Is K2-401 b?
K2-401 b has a radius of 2.26 times that of Earth.
Is K2-401 b in the Habitable Zone?
The position of K2-401 b relative to the habitable zone of K2-401 cannot be precisely determined from the available orbital data.
Habitable zone of K2-401: 0.290–0.725 AU (conservative: 0.367–0.688 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 ›
Orbit and Year Length
A year on K2-401 b — one full orbit around K2-401 — lasts 6.29 Earth days, shorter than Mercury's 88-day year.
How Was K2-401 b Discovered?
K2-401 b was discovered in 2022 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 K2-401 b?
K2-401 b is 654.7 light-years (200.7 parsecs) from Earth. Light arriving here tonight left the planet around the year 1372. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,522,720 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. K2-401 b scores 0.28, ranking #2,351 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-401
K2-401
- Surface temperature
- 4,213 K (Sun: 5,772 K)
- Mass
- 0.87 M☉
- Radius
- 0.68 R☉
Planetary System
K2-401 b is the only planet known to orbit K2-401 so far.
K2-401 b — Complete Data
| Radius | 2.262 Earth radii (0.202 Jupiter radii) |
|---|---|
| Orbital period | 6.29 days |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 654.7 light-years (200.7 parsecs) |
| Constellation | Sextans |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2022-03-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-401 b
Is K2-401 b habitable?
K2-401 b is not known to orbit within the habitable zone of K2-401, and as a mini-Neptune it is an unlikely candidate for life as we know it.
How far away is K2-401 b?
K2-401 b is about 655 light-years from Earth in the constellation Sextans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,522,720 years to get there.
How big is K2-401 b compared to Earth?
K2-401 b has 2.26 times the radius of Earth.
How long is a year on K2-401 b?
One orbit around K2-401 takes 6.3 Earth days — short enough that 58 of its years would fit into one Earth year.
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