These deformations can create enough internal friction to substantially heat the planet’s interior and produce volcanic activity at its surface. On this elliptical path, planet d is slightly deformed every time it goes around the star. Each close pass by the more massive planet c produces a gravitational tug on planet d, making its orbit somewhat elliptical. The outer planet c is about 2.5 times Earth’s size and more than seven times its mass.ĭuring each orbit, planets d and c pass very close to each other. The inner planet b is about 20% bigger than Earth. The team estimates it’s only slightly larger and more massive than Earth.Īstronomers already knew about two other worlds in the system before this discovery, called LP 791-18 b and c.

LP 791-18 d orbits a small red dwarf star about 90 light-years away in the southern constellation Crater. 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 day side would probably be too hot for liquid water to exist on the surface. They found and studied the planet using data from NASA’s TESS (Transiting Exoplanet Survey Satellite) and retired Spitzer Space Telescope, as well as a suite of ground-based observatories.Ī paper about the planet – led by Merrin Peterson, a graduate of the Trottier Institute for Research on Exoplanets (iREx) based at the University of Montreal – appears in the May 17 edition of the scientific journal Nature.“LP 791-18 d is tidally locked, which means the same side constantly faces its star,” said Björn Benneke, a co-author and astronomy professor at iREx who planned and supervised the study.

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