K2-287 b
K2-287 b is a cold gas giant orbiting K2-287 in the constellation Libra. It lies about 516 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is K2-287 b?
K2-287 b has a radius of 9.49 times that of Earth, or 0.85 times the radius of Jupiter. Its mass is 100 times that of Earth.
Is K2-287 b in the Habitable Zone?
K2-287 b orbits inside the inner edge of the habitable zone of K2-287. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-287: 0.784–1.851 AU (conservative: 0.993–1.755 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-287 b
The equilibrium temperature of K2-287 b is about 804 K (531 °C) — hot enough to melt many metals. 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 K2-287 b — one full orbit around K2-287 — lasts 14.9 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.121 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.48), swinging dramatically closer to and farther from its star.
How Was K2-287 b Discovered?
K2-287 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 K2-287 b?
K2-287 b is 516.4 light-years (158.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1510. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 9,088,640 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. K2-287 b scores 0.11, ranking #4,387 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-287
K2-287
- Surface temperature
- 5,695 K (Sun: 5,772 K)
- Mass
- 1.06 M☉
- Radius
- 1.07 R☉
- Age
- 4.5 billion years (Sun: 4.6)
Planetary System
K2-287 b is the only planet known to orbit K2-287 so far.
K2-287 b — Complete Data
| Radius | 9.494 Earth radii (0.847 Jupiter radii) |
|---|---|
| Mass | 100.12 Earth masses (0.315 Jupiter masses) |
| Orbital period | 14.89 days |
| Orbital distance | 0.121 AU |
| Eccentricity | 0.478 |
| Equilibrium temperature | 804 K (531 °C) |
| Earth Similarity Index | 0.11 |
| Distance from Earth | 516.4 light-years (158.3 parsecs) |
| Constellation | Libra |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2019-01-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-287 b
Is K2-287 b habitable?
No — K2-287 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-287 b?
K2-287 b is about 516 light-years from Earth in the constellation Libra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 9,088,640 years to get there.
How big is K2-287 b compared to Earth?
K2-287 b has 9.49 times the radius of Earth and about 100 times its mass.
How long is a year on K2-287 b?
One orbit around K2-287 takes 14.9 Earth days — short enough that 25 of its years would fit into one Earth year.
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