K2-291 b
K2-291 b is a super-Earth orbiting K2-291 in the constellation Taurus. It lies about 294 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is K2-291 b?
K2-291 b has a radius of 1.59 times that of Earth. Its mass is 6.5 times that of Earth, giving it a density of 8.84 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is K2-291 b in the Habitable Zone?
K2-291 b orbits inside the inner edge of the habitable zone of K2-291. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-291: 0.629–1.494 AU (conservative: 0.797–1.416 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-291 b
K2-291 b receives 633 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-291 b — one full orbit around K2-291 — lasts 2.23 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.033 AU — closer to its star than Mercury is to the Sun.
How Was K2-291 b Discovered?
K2-291 b 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 K2-291 b?
K2-291 b is 293.7 light-years (90.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1733. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,169,120 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. K2-291 b scores 0.28, ranking #2,360 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-291
K2-291
- Surface temperature
- 5,520 K (Sun: 5,772 K)
- Mass
- 0.93 M☉
- Radius
- 0.90 R☉
- Luminosity
- 0.6820 L☉
- Age
- 3.7 billion years (Sun: 4.6)
Planetary System
K2-291 b is the only planet known to orbit K2-291 so far.
K2-291 b — Complete Data
| Radius | 1.589 Earth radii (0.142 Jupiter radii) |
|---|---|
| Mass | 6.49 Earth masses (0.020 Jupiter masses) |
| Density | 8.84 g/cm³ (Earth: 5.51) |
| Orbital period | 2.23 days |
| Orbital distance | 0.033 AU |
| Stellar irradiation | 633.00× Earth |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 293.7 light-years (90.1 parsecs) |
| Constellation | Taurus |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-01-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-291 b
Is K2-291 b habitable?
No — K2-291 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-291 b?
K2-291 b is about 294 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,169,120 years to get there.
How big is K2-291 b compared to Earth?
K2-291 b has 1.59 times the radius of Earth and about 6.5 times its mass.
How long is a year on K2-291 b?
One orbit around K2-291 takes 2.2 Earth days — short enough that 164 of its years would fit into one Earth year.
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