Astronomers have identified an Earth-sized world that may be volcanically active beyond our solar system. The finding comes from NASA-supported research and the analysis of multiple space-based and ground-based observatories.
Planet LP 791-18 d orbits a red dwarf about 90 light-years away in the southern region of the sky known as the Chalice constellation. Researchers estimate that this planet is only slightly larger and more massive than Earth. It is also tidally locked, meaning one face forever basks in starlight while the other remains in darkness. The detection relied on data from the Transiting Exoplanet Survey Satellite, the Spitzer Space Telescope, and several ground facilities working together to confirm the signal.
Because of tidal locking, the sunward side of the planet is expected to be extremely hot, making liquid water unlikely there. Yet analyses reveal that LP 791-18 d repeatedly passes near a larger companion planet, LP 791-18 s. The gravitational pull between these worlds stretches the orbit of planet d into an ellipse. That tidal deformation causes internal friction and heating, a process known for driving geologic activity on moons in our own solar system. Scientists infer that tidal warming may trigger regular volcanic eruptions on d, akin to volcanic activity seen on Io and other Galilean moons orbiting Jupiter. The eruptions could release gases that build a thin atmosphere, possibly creating conditions on the planet’s night side where liquid water might briefly exist under the right pressures and temperatures.
The dynamic environment around LP 791-18 d is shaped by the gravitational interaction with LP 791-18 s. As planet d moves along its elongated orbit, tidal forces continually shape its interior, potentially fueling a cycle of volcanic output that influences the planet’s surface and atmospheric development. The overall scenario offers a vivid example of how planetary systems can differ dramatically from our own, yet still harbor processes that resemble familiar geological activity observed within our solar system. The discovery underscores how combined observations from multiple telescopes can reveal complex planetary dynamics and surface conditions on worlds far beyond Earth.
In the broader context of exoplanet research, findings like this help scientists refine models of tidal heating, atmospheric formation, and the potential for exotic climates on rocky planets around small, cooler stars. While LP 791-18 d may not host surface oceans, its atmospheric and volcanic activity provides crucial data on how heat and materials circulate in tidally influenced worlds. Ongoing observations aim to map the planet’s orbit in greater detail and to search for signatures of gas species that could hint at atmospheric composition, weather patterns, and the faint glow of volcanic plumes in infrared light. These insights contribute to the broader quest to understand how common Earth-like processes are in distant planetary systems and what conditions might make such worlds candidates for future study, even when oceans are not present on the day side of the planet.