Astronomers discover Earth-sized exoplanet — with one side in perpetual darkness — that is likely covered with volcanoes
An Earth-sized planet orbiting a star beyond our solar system is likely covered with volcanoes, researchers have concluded.
The planet is technically an exoplanet, meaning it is beyond our solar system. In a scientific paper outlining the discovery, researchers dubbed it LP 791-18 d. It was discovered while researchers were studying a small star, already known to host two larger planets. Those two bodies were discovered in June 2019 with NASA's Transiting Exoplanet Survey Satellite (TESS). Further observations using the TESS and the retired NASA Spitzer Space Telescope detected LP 791-18 d.
The planet is in the Milky Way, about 86 light-years away from our own solar system. A light year is the equivalent to the distance light travels in a year, or about 5.9 trillion miles.
The researchers' observations suggest that the planet is rugged and rocky, with constant eruptions from volcanoes on the surface. Scientists didn't directly see the volcanoes, but instead used observations of the way the planet interacts with one of the other larger planets orbiting the same dim star. The larger planet has a strong gravitational tug, which may cause the newer, smaller one to squeeze and flex, heating the interior and causing volcanic activity on the surface. Observations show the smaller planet is deformed every time it goes around the star. The movement is comparable to Io, a moon of Jupiter, which is the most volcanically active body in our solar system.
The planet, which does not rotate, may also hold water, researchers said. One side of the planet is too hot, but the other side remains in permanent night, which scientists said could "plausibly" allow for water condensation.
"LP 791-18 d is tidally locked, which means the same side constantly faces its star," Björn Benneke, a co-author and astronomy professor at the University of Montreal's the Trottier Institute for Research on Exoplanets who planned and supervised the study, told NASA. "The day side would probably be too hot for liquid water to exist on the surface. But the amount of volcanic activity we suspect occurs all over the planet could sustain an atmosphere, which may allow water to condense on the night side."
The planet may also be able to sustain an atmosphere, the research team said, though what kind of atmosphere the planet is capable of hosting will vary based on its formation history.
One of the larger planets near LP 791-18 d has been approved for further study using the James Webb Space Telescope, NASA said. The research team believes that the new planet could also be an "exceptional candidate for atmospheric studies."