K2-66 b
K2-66 b is a super-Earth orbiting K2-66 in the constellation Aquarius. It lies about 1,676 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is K2-66 b?
K2-66 b has a radius of 2.49 times that of Earth. Its mass is 21.3 times that of Earth, giving it a density of 7.80 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is K2-66 b in the Habitable Zone?
K2-66 b orbits inside the inner edge of the habitable zone of K2-66. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-66: 1.292–3.037 AU (conservative: 1.637–2.879 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-66 b
The equilibrium temperature of K2-66 b is about 1,372 K (1,099 °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. It receives 840 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-66 b — one full orbit around K2-66 — lasts 5.07 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.060 AU — closer to its star than Mercury is to the Sun.
How Was K2-66 b Discovered?
K2-66 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 K2-66 b?
K2-66 b is 1,676.0 light-years (513.9 parsecs) from Earth. Light arriving here tonight left the planet about 1,676 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 29,497,600 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. K2-66 b scores 0.23, ranking #3,464 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-66
K2-66
- Surface temperature
- 5,887 K (Sun: 5,772 K)
- Mass
- 1.11 M☉
- Radius
- 1.67 R☉
Planetary System
K2-66 b is the only planet known to orbit K2-66 so far.
K2-66 b — Complete Data
| Radius | 2.490 Earth radii (0.222 Jupiter radii) |
|---|---|
| Mass | 21.30 Earth masses (0.067 Jupiter masses) |
| Density | 7.80 g/cm³ (Earth: 5.51) |
| Orbital period | 5.07 days |
| Orbital distance | 0.060 AU |
| Equilibrium temperature | 1,372 K (1,099 °C) |
| Stellar irradiation | 840.00× Earth |
| Earth Similarity Index | 0.23 |
| Distance from Earth | 1,676.0 light-years (513.9 parsecs) |
| Constellation | Aquarius |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2019-07-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-66 b
Is K2-66 b habitable?
No — K2-66 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-66 b?
K2-66 b is about 1,676 light-years from Earth in the constellation Aquarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 29,497,600 years to get there.
How big is K2-66 b compared to Earth?
K2-66 b has 2.49 times the radius of Earth and about 21.3 times its mass.
How long is a year on K2-66 b?
One orbit around K2-66 takes 5.1 Earth days — short enough that 72 of its years would fit into one Earth year.
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