LHS 1140 b
LHS 1140 b is a super-Earth orbiting the M4.5 V star LHS 1140 in the constellation Cetus. It lies about 49 light-years from Earth and was discovered in 2017 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 LHS 1140 b?
LHS 1140 b has a radius of 1.73 times that of Earth. Its mass is 5.6 times that of Earth, giving it a density of 5.90 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is LHS 1140 b in the Habitable Zone?
LHS 1140 b orbits inside the conservative habitable zone of LHS 1140 — 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 LHS 1140: 0.051–0.134 AU (conservative: 0.064–0.127 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on LHS 1140 b
The equilibrium temperature of LHS 1140 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. It receives 0.43 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on LHS 1140 b — one full orbit around LHS 1140 — lasts 24.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.095 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.043).
How Was LHS 1140 b Discovered?
LHS 1140 b was discovered in 2017 using the transit method, with observations from MEarth Project.
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 LHS 1140 b?
LHS 1140 b is 48.9 light-years (15.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1978. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 860,640 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. LHS 1140 b scores 0.66, ranking #90 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: LHS 1140
LHS 1140
- Spectral type
- M4.5 V
- Surface temperature
- 3,096 K (Sun: 5,772 K)
- Mass
- 0.18 M☉
- Radius
- 0.22 R☉
- Luminosity
- 0.0038 L☉
- Age
- 5.0 billion years (Sun: 4.6)
The LHS 1140 Planetary System
LHS 1140 b is one of 2 known planets in the LHS 1140 system. Its siblings:
- LHS 1140 c (Super Earth)
LHS 1140 b — Complete Data
| Radius | 1.730 Earth radii (0.154 Jupiter radii) |
|---|---|
| Mass | 5.60 Earth masses (0.018 Jupiter masses) |
| Density | 5.90 g/cm³ (Earth: 5.51) |
| Orbital period | 24.74 days |
| Orbital distance | 0.095 AU |
| Eccentricity | 0.043 |
| Equilibrium temperature | 226 K (-47 °C) |
| Stellar irradiation | 0.43× Earth |
| Earth Similarity Index | 0.66 |
| Distance from Earth | 48.9 light-years (15.0 parsecs) |
| Constellation | Cetus |
| Discovery method | Transit |
| Discovery facility | MEarth Project |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2024-03-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About LHS 1140 b
Is LHS 1140 b habitable?
LHS 1140 b orbits within the habitable zone of LHS 1140, 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 LHS 1140 b?
LHS 1140 b is about 49 light-years from Earth in the constellation Cetus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 860,640 years to get there.
How big is LHS 1140 b compared to Earth?
LHS 1140 b has 1.73 times the radius of Earth and about 5.6 times its mass.
How long is a year on LHS 1140 b?
One orbit around LHS 1140 takes 24.7 Earth days — short enough that 15 of its years would fit into one Earth year.
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