K2-133 e
K2-133 e is a super-Earth orbiting the M1.5 V star K2-133 in the constellation Taurus. It lies about 245 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is K2-133 e?
K2-133 e has a radius of 1.73 times that of Earth.
Is K2-133 e in the Habitable Zone?
K2-133 e orbits inside the inner edge of the habitable zone of K2-133. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-133: 0.149–0.383 AU (conservative: 0.188–0.363 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-133 e
The equilibrium temperature of K2-133 e is about 296 K (23 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 1.80 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-133 e — one full orbit around K2-133 — lasts 26.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.135 AU — closer to its star than Mercury is to the Sun.
How Was K2-133 e Discovered?
K2-133 e 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 K2-133 e?
K2-133 e is 245.2 light-years (75.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1781. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,315,520 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. K2-133 e scores 0.72, ranking #50 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: K2-133
K2-133
- Spectral type
- M1.5 V
- Surface temperature
- 3,655 K (Sun: 5,772 K)
- Mass
- 0.46 M☉
- Radius
- 0.46 R☉
- Luminosity
- 0.0332 L☉
The K2-133 Planetary System
K2-133 e is one of 4 known planets in the K2-133 system. Its siblings:
K2-133 e — Complete Data
| Radius | 1.730 Earth radii (0.154 Jupiter radii) |
|---|---|
| Orbital period | 26.58 days |
| Orbital distance | 0.135 AU |
| Equilibrium temperature | 296 K (23 °C) |
| Stellar irradiation | 1.80× Earth |
| Earth Similarity Index | 0.72 |
| Distance from Earth | 245.2 light-years (75.2 parsecs) |
| Constellation | Taurus |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-05-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-133 e
Is K2-133 e habitable?
No — K2-133 e orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-133 e?
K2-133 e is about 245 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,315,520 years to get there.
How big is K2-133 e compared to Earth?
K2-133 e has 1.73 times the radius of Earth.
How long is a year on K2-133 e?
One orbit around K2-133 takes 26.6 Earth days — short enough that 14 of its years would fit into one Earth year.
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