Synopsis
Here is a summary of the key points from the paper “New Mass and Radius Constraints on the LHS 1140 Planets: LHS 1140 b Is either a Temperate Mini-Neptune or a Water World”:
- The paper presents improved mass and radius measurements for the two planets orbiting the nearby M dwarf star LHS 1140.
- The mass of planet b is determined to be 5.60 ± 0.19 M⊕ and its radius is 1.730 ± 0.025 R⊕. For planet c, the mass is 1.91 ± 0.06 M⊕ and radius is 1.272 ± 0.026 R⊕.
- These precise measurements rule out a purely rocky composition for planet b. It is likely either a mini-Neptune with a thin hydrogen envelope making up ~0.1% of the planet’s mass or a water world with 9-19% water content by mass.
- Climate models show planet b could support liquid water at the substellar point if it has an atmosphere with less than a few bars of CO2. Higher CO2 would extend the habitable area.
- Transmission spectroscopy with JWST should be able to distinguish between a hydrogen-rich atmosphere and a more heavy-element atmosphere for planet b. At least 18 additional transits will need to be observed to detect an Earth-like, low CO2 atmosphere.
In summary, the paper refines our understanding of the internal structure and potential habitability of LHS 1140 b thanks to improved measurements and modeling. JWST will further probe the nature of this nearby temperate planet’s atmosphere.
