K2-201 b
K2-201 b is a super-Earth orbiting K2-201 in the constellation Sagittarius. It lies about 646 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-201 b?
K2-201 b has a radius of 1.40 times that of Earth.
Is K2-201 b in the Habitable Zone?
The position of K2-201 b relative to the habitable zone of K2-201 cannot be precisely determined from the available orbital data.
Habitable zone of K2-201: 0.608–1.444 AU (conservative: 0.770–1.369 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 K2-201 b — one full orbit around K2-201 — lasts just 25.4 hours, shorter than Mercury's 88-day year.
How Was K2-201 b Discovered?
K2-201 b was discovered in 2018 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 K2-201 b?
K2-201 b is 645.6 light-years (197.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1381. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,362,560 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. K2-201 b scores 0.28, ranking #2,105 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-201
K2-201
- Surface temperature
- 5,507 K (Sun: 5,772 K)
- Mass
- 0.96 M☉
- Radius
- 0.88 R☉
The K2-201 Planetary System
K2-201 b is one of 2 known planets in the K2-201 system. Its siblings:
- K2-201 c (Sub Neptune)
K2-201 b — Complete Data
| Radius | 1.400 Earth radii (0.125 Jupiter radii) |
|---|---|
| Orbital period | 1.06 days |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 645.6 light-years (197.9 parsecs) |
| Constellation | Sagittarius |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-02-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-201 b
Is K2-201 b habitable?
K2-201 b is not known to orbit within the habitable zone of K2-201, and as a super-Earth it is an unlikely candidate for life as we know it.
How far away is K2-201 b?
K2-201 b is about 646 light-years from Earth in the constellation Sagittarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,362,560 years to get there.
How big is K2-201 b compared to Earth?
K2-201 b has 1.40 times the radius of Earth.
How long is a year on K2-201 b?
One orbit around K2-201 takes 1.1 Earth days — short enough that 345 of its years would fit into one Earth year.
Explore K2-201 b in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
