Astronomers detected escaping helium from the rocky exoplanet LHS 1140b (48–49 light‑years; constellation Cetus) using the Magellan Clay Telescope, confirming an extended, helium‑rich upper atmosphere in a temperate orbit.
Planetary parameters
- Location & type: LHS 1140b — rocky super‑Earth in the host star’s habitable zone.
- Mass & radius: 5.6 Earth masses; 1.73 Earth radii.
- System context: Companion LHS 1140c is closer to the star, receives ≈5× stellar flux, and shows no detected atmosphere.
Helium detection & method
- Observations: Warm Infrared Echelle Spectrograph at Magellan Clay Telescope, Las Campanas Observatory.
- Spectral tracer: He I 10830 Å triplet (1.083 µm) probes extended, escaping helium in upper atmospheres.
- Temporal behaviour: Clear helium signal in 2024; nondetection in 2025 — evidence for time‑variable atmospheric escape.
Atmospheric physics
- Escape mechanisms: Photoevaporation, hydrodynamic escape and Jeans escape govern volatile loss; helium efficiently traces upper‑atmosphere loss.
- Vertical structure: Helium‑rich upper layer can coexist with heavier volatiles (e.g. H2O) at lower altitudes.
- Evolutionary note: Atmosphere present for ≥3.1 billion years, constraining atmospheric retention timescales for temperate rocky planets.
IASPOINT Booster Facts
- Super‑Earth: Planet larger than Earth but smaller than Uranus/Neptune.
- Habitable zone: Orbital region permitting liquid water given sufficient atmospheric pressure and composition.
- Key observatories: High‑resolution ground spectrographs plus JWST and HST are primary tools for exoplanet atmosphere studies.