LP 791-18 d, shown here in an artist’s concept (NASA)
NASA’s TESS (Transiting Exoplanet Survey Satellite) discovered an Earth-size exoplanet – world beyond our solar system –with one very big difference: NASA says the world may be carpeted with volcanoes. Called LP 791-18 d, the planet could undergo volcanic outbursts as often as Jupiter’s moon Io, the most volcanically active body in our solar system. Scientists found and studied the planet using data from NASA’s TESS and retired Spitzer Space Telescope, as well as a suite of ground-based observatories.
This is all important because scientists are trying to find new worlds somewhere out there where people could possibly live someday. But don’t get too excited about colonizing other planets. It will be at least a century before we have anywhere near the technology needed to travel to other star systems. And even then, unless we figure out a way to travel faster than light, it will take centuries to get anywhere.
TESS, launched on April 18, 2018, is an all-sky survey mission discovering exoplanets around nearby bright stars.
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“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. “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.”
LP 791-18 d orbits a small red dwarf star about 90 light-years away in the southern constellation Crater. The team estimates it’s only slightly larger and more massive than Earth.
Astronomers already knew about two other worlds in the system before this discovery, called LP 791-18 b and c. The inner planet b is about 20% bigger than Earth. The outer planet c is about 2.5 times Earth’s size and more than seven times its mass.
NASA explains during each orbit, planets d and c pass very close to each other. Each close pass by the more massive planet c produces a gravitational tug on planet d, making its orbit somewhat elliptical. On this elliptical path, planet d is slightly deformed every time it goes around the star. These deformations can create enough internal friction to substantially heat the planet’s interior and produce volcanic activity at its surface. Jupiter and some of its moons affect Io in a similar way.
Planet d sits on the inner edge of the habitable zone, the traditional range of distances from a star where scientists hypothesize liquid water could exist on a planet’s surface. If the planet is as geologically active as the research team suspects, it could maintain an atmosphere. Temperatures could drop enough on the planet’s night side for water to condense on the surface.
Planet c has already been approved for observing time on the James Webb Space Telescope, and the team thinks planet d is also an exceptional candidate for atmospheric studies by the mission.
“A big question in astrobiology, the field that broadly studies the origins of life on Earth and beyond, is if tectonic or volcanic activity is necessary for life,” said co-author Jessie Christiansen, a research scientist at NASA’s Exoplanet Science Institute at the California Institute of Technology in Pasadena. “In addition to potentially providing an atmosphere, these processes could churn up materials that would otherwise sink down and get trapped in the crust, including those we think are important for life, like carbon.”
