Astronomers have discovered an Earth-sized exoplanet, or world beyond our solar system, that may be covered in volcanoes. The planet, called LP 791-18 d, may have been subject to volcanic eruptions as often as Jupiter’s moon Io, the most volcanically active body in our solar system.
They found and studied the planet using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the retired Spitzer Space Telescope, as well as a suite of ground-based observatories.
The paper on the planet led by Merrin Peterson, a graduate of the University of Montreal’s Trottier Institute for Exoplanet Research (iREx) appears in the May 17 issue of the science journal Nature.
“LP 791-18 d is tidally locked, meaning that the same side faces its star all the time,” said Björn Benneke, co-author and professor of astronomy at iREx, who planned and supervised the study.
“The day side would probably be too hot for liquid water to exist on the surface. But the amount of volcanic activity we believe occurs across the planet could sustain an atmosphere, which may allow water to condense on the night side.
Red dwarf about 90 light-years away in the southern constellation Crater
LP 791-18 d orbits a small red dwarf about 90 light-years away in the southern constellation Crater. The team estimates that it is only slightly larger and more massive than Earth.
Before this discovery, astronomers already knew of two other worlds in the system, called LP 791-18 b and c. The inner planet b is about 20% larger than Earth. Outer planet c is about 2.5 times the size of Earth and more than seven times its mass.
During each orbit the dac planets pass very close to each other. Each close flyby of the more massive planet c exerts a gravitational pull on planet d, making its orbit somewhat elliptical. In this elliptical orbit, planet d is slightly deformed each time it orbits the star.
These deformations can create enough internal friction to substantially heat a planet’s interior and trigger volcanic activity on its surface. Jupiter and some of its moons influence Io in a similar way.
Planet d lies at the inner edge of the habitable zone, the traditional range of distances from a star where scientists think liquid water could exist on a planet’s surface. If the planet is as geologically active as the research team believes, it could retain an atmosphere. Temperatures on the night side of the planet could drop enough that water could condense on the surface.
Planet c has already been approved for time observations on the James Webb Space Telescope, and the team believes that planet d is also an exceptional candidate for the mission’s atmospheric studies.
California Institute of Technology Pasadena. “In addition to potentially creating an atmosphere, these processes could spew out materials that would otherwise sink and become trapped in the crust, including those we think are important for life, such as carbon.”
Spitzer’s observations of the system were among the last the satellite collected before it was decommissioned in January 2020.
“It’s incredible to read about continued discoveries and publications years after the Spitzer mission ended,” said Joseph Hunt, Spitzer project manager at NASA’s Jet Propulsion Laboratory in Southern California. “This really shows the success of our world-class engineers and scientists. Together, they built not only a spacecraft, but also a dataset that continues to benefit the astrophysics community.
TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts and managed by NASA’s Goddard Space Flight Center. The entire body of science data collected by Spitzer during its existence is available to the public through the Spitzer Data Archive, located at the Infrared Science Archive at IPAC at Caltech in Pasadena, California.
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