Super-Earth · possible water-rich world
LHS 1140 b
The best current combination of a temperate planet, a nearby star, and a potentially characterizable atmosphere.
- Orbital period
- 24.737 days
- Semi-major axis
- Unknown
- Radius
- 1.73 R⊕
- Mass
- 5.6 M⊕
- Equilibrium temperature
- 226 K
- Stellar flux
- 0.43 S⊕
Accelerated orbits · real relative periods · compressed sizes and distancesAxial rotation is not shown because it is generally unknown.
- Distance?The separation between Earth and the planetary system, measured in light-years. One light-year is the distance light travels in one year.
- 48.9 light-years
- Radius?Half the planet’s diameter. R⊕ compares this size with Earth’s radius; 1.5 R⊕ means a radius 50% larger than Earth’s.
- 1.73 R⊕
- Mass?The amount of matter in the planet. M⊕ uses Earth as the unit. With radial velocity, the reported value may be only the minimum mass.
- 5.60 M⊕
- Orbit?The time the planet takes to complete one revolution around its star — the equivalent of its year.
- 24.737 days
- Flux / T_eq?Flux is the energy the planet receives from its star, compared with Earth. Equilibrium temperature is a simplified calculation that does not include climate, clouds, or the greenhouse effect.
- 0.43 S⊕ · 226 ± 4 K
- Star?The type and behavior of the host star. M stars are small and cool, but many produce flares that can affect planetary atmospheres.
- M4.5 V · old and relatively quiet
Seeing this system means seeing it as it was 48.9 years ago.
A mental comparison at the probe’s current speed, not a proposed journey.
Radius, mass, and atmosphere are inferred from light, motion, and physical models.
Webb ruled out a primordial H₂-rich atmosphere; ground-based spectroscopy published in 2026 reported variable escaping helium in the upper atmosphere, without confirming a heavy atmosphere near the surface.
Observed
Radius, mass, and incident flux are well measured; Webb ruled out a primordial H₂ atmosphere, and ground-based spectroscopy detected variable helium in the upper atmosphere.
Inferred
The density and spectrum favor a water-rich planet or one with a heavy atmosphere, but alternative scenarios remain viable.
Still speculative
A high-molecular-weight atmosphere has not yet been confirmed unambiguously. Ocean, ice, and continents remain model scenarios, not observations.
Next test
Additional transits and thermal observations need to search for CO₂ and separate the planetary signal from stellar activity.