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Studies question habitability of TRAPPIST-1 planets

This artist's illustration shows what the seven TRAPPIST-1 planets may look like, based on available data about their diameters, masses and distances from the host star. Credit: NASA/JPL-Caltech

The stellar wind and ultraviolet radiation from red dwarf star TRAPPIST-1 might make all seven of its planets uninhabitable for life as we know it, in spite of three planets being in its habitable zone, according to two separate studies.

Both studies were headed by scientists at the Harvard-Smithsonian Center for Astrophysics.

Manasvi Lingam led the first study, which determined that planets orbiting TRAPPIST-1 would be bombarded intensely by far more ultraviolet radiation than the Earth receives from the Sun.

While red dwarfs are less massive and fainter than Sun-like stars, many emit high-energy flares of ultraviolet radiation.

That radiation could strip the atmospheres of all the system’s planets, rendering them uninhabitable.

Additionally, the researchers considered the effects of temperature on the possible evolution of life.

“The concept of a habitable zone is based on planets being in orbits where liquid water could exist. This is only one factor, however, in determining whether a planet is hospitable for life,” Lingam said.

Avi Loeb, who with Lingam co-authored a study on the system published in the International Journal of Astrobiology, noted, “Because of the onslaught by the star’s radiation, our results suggest the atmospheres on planets in the TRAPPIST-1 system would largely be destroyed. This would hurt the chances of life forming or persisting.”

The other study addressed a second threat to life on any of the TRAPPIST-1 planets, specifically pressure from the stellar wind, made up of particles streaming from the star into space.

According to their calculations, that pressure would be between 1,000 and 100,000 times that exerted by the solar wind on Earth.

This could cause the magnetic fields of the star and of its planets to connect with one another, setting into motion a process that could strip the planet’s atmosphere completely.

While Earth’s magnetic field protects the planet from such a process being triggered by the solar wind, that would not be the case if our planet were closer to the Sun and subject to the levels of solar wind exposure faced by the TRAPPIST-1 planets, said Cecilia Garraffo, leader of this study.

Findings of the study have been published in The Astrophysical Journal Letters.

Scientists on both studies do not completely rule out the chance of life taking hold on planets orbiting red dwarf stars or even on the TRAPPIST-1 planets; however, they recommend concentrating the search for extra-terrestrial life on worlds orbiting Sun-like stars.

Laurel Kornfeld

Laurel Kornfeld

Staff Writer
Laurel Kornfeld is a freelance writer and amateur astronomer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science in astronomy from Swinburne University’s Astronomy Online program.
About Laurel Kornfeld (1100 Articles)
Laurel Kornfeld is a freelance writer and amateur astronomer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science in astronomy from Swinburne University’s Astronomy Online program.