K2-91 b
K2-91 b is a terrestrial planet orbiting K2-91 in the constellation Taurus. It lies about 204 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is K2-91 b?
K2-91 b has a radius of 1.10 times that of Earth.
Is K2-91 b in the Habitable Zone?
K2-91 b orbits inside the inner edge of the habitable zone of K2-91. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-91: 0.091–0.235 AU (conservative: 0.115–0.223 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 K2-91 b
K2-91 b receives 46.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-91 b — one full orbit around K2-91 — lasts just 34.1 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.016 AU — closer to its star than Mercury is to the Sun.
How Was K2-91 b Discovered?
K2-91 b was discovered in 2016 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 K2-91 b?
K2-91 b is 204.1 light-years (62.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1822. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,592,160 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. K2-91 b scores 0.32, ranking #1,043 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-91
K2-91
- Surface temperature
- 3,622 K (Sun: 5,772 K)
- Mass
- 0.29 M☉
- Radius
- 0.28 R☉
Planetary System
K2-91 b is the only planet known to orbit K2-91 so far.
K2-91 b — Complete Data
| Radius | 1.100 Earth radii (0.098 Jupiter radii) |
|---|---|
| Orbital period | 1.42 days |
| Orbital distance | 0.016 AU |
| Stellar irradiation | 46.00× Earth |
| Earth Similarity Index | 0.32 |
| Distance from Earth | 204.1 light-years (62.6 parsecs) |
| Constellation | Taurus |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-07-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-91 b
Is K2-91 b habitable?
No — K2-91 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-91 b?
K2-91 b is about 204 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,592,160 years to get there.
How big is K2-91 b compared to Earth?
K2-91 b has 1.10 times the radius of Earth.
How long is a year on K2-91 b?
One orbit around K2-91 takes 1.4 Earth days — short enough that 257 of its years would fit into one Earth year.
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