K2-288 B b
K2-288 B b is a super-Earth orbiting the M3 V star K2-288 B in the constellation Taurus. It lies about 214 light-years from Earth and was discovered in 2018 using the transit method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
How Big Is K2-288 B b?
K2-288 B b has a radius of 1.90 times that of Earth.
Is K2-288 B b in the Habitable Zone?
K2-288 B b orbits inside the conservative habitable zone of K2-288 B — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of K2-288 B: 0.089–0.232 AU (conservative: 0.112–0.220 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-288 B b
The equilibrium temperature of K2-288 B b is about 226 K (-47 °C) — well below freezing. 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 K2-288 B b — one full orbit around K2-288 B — lasts 31.4 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.164 AU — closer to its star than Mercury is to the Sun.
How Was K2-288 B b Discovered?
K2-288 B 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 K2-288 B b?
K2-288 B b is 214.0 light-years (65.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1812. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,766,400 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. K2-288 B b scores 0.65, ranking #100 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-288 B
K2-288 B b belongs to a system of 2 stars; it orbits K2-288 B.
K2-288 B
- Spectral type
- M3 V
- Surface temperature
- 3,341 K (Sun: 5,772 K)
- Mass
- 0.33 M☉
- Radius
- 0.32 R☉
- Luminosity
- 0.0117 L☉
- Age
- 1.0 billion years (Sun: 4.6)
Planetary System
K2-288 B b is the only planet known to orbit K2-288 B so far.
K2-288 B b — Complete Data
| Radius | 1.900 Earth radii (0.170 Jupiter radii) |
|---|---|
| Orbital period | 31.39 days |
| Orbital distance | 0.164 AU |
| Equilibrium temperature | 226 K (-47 °C) |
| Earth Similarity Index | 0.65 |
| Distance from Earth | 214.0 light-years (65.6 parsecs) |
| Constellation | Taurus |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2019-01-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-288 B b
Is K2-288 B b habitable?
K2-288 B b orbits within the habitable zone of K2-288 B, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is K2-288 B b?
K2-288 B b is about 214 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,766,400 years to get there.
How big is K2-288 B b compared to Earth?
K2-288 B b has 1.90 times the radius of Earth.
How long is a year on K2-288 B b?
One orbit around K2-288 B takes 31.4 Earth days — short enough that 12 of its years would fit into one Earth year.
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