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TRAPPIST-1 Planets May Be Far More Habitable Than We First Thought

The exoplanets orbiting around our neighboring star TRAPPIST-1 may have more of a chance of having life present than we previously thought.

According to a preprint report due to be published in the journal Astronomy and Astrophysics, TRAPPIST-1 emits solar flares that may provide the planets enough energy for life to evolve.

TRAPPIST-1 is a red dwarf star located around 40.7 light years away from our solar system. Four of its seven planets are situated in the Goldilocks zone, which is the band of space around a star where the temperatures enable liquid water to exist on the surface. Its relative proximity to Earth (our Milky Way galaxy is around 100,000 light-years across, for reference) and its multiple Goldilocks planets have made TRAPPIST-1 a focal point for the search for life on other planets.

"Cool red dwarf stars like TRAPPIST-1 are the most common type of stars (75 percent of stars in the Milky Way), so if we are looking for life on exoplanets around other stars, these types of stars are of high interest. In fact, our closest star Proxima Centauri is also a red dwarf and also has a planet Proxima Centauri b in the traditional habitable zone—i.e. liquid water," Laura McKemmish, a quantum chemist and molecular physicist at the University of New South Wales, told Newsweek.

"But red dwarf stars are much more volatile than hotter stars like our sun and experience a much higher rate of stellar flares," she said. "These stellar flares and associated coronal mass ejections emit deadly radiation and so the habitability of planets around red dwarfs is highly uncertain because it is expected these frequent and strong stellar flares would destroy the habitability of the planet (e.g. unstable atmospheric composition, radiation destroying life molecules once it gets through the atmosphere, etc)."

There is a current debate in the scientific community about whether the enhanced stellar weather on red dwarf stars precludes life from existing within planets around these stars, according to McKemmish.

"Although high energetic radiation from flares is a potential threat to exoplanet atmospheres and may lead to surface sterilization, it might also provide the extra energy for low-mass stars needed to trigger and sustain prebiotic chemistry," wrote the authors in the abstract of the preprint report.

Their analysis of the black-body radiation of the star found lower-than-expected flare temperatures, which would affect the radiation emitted and thus potentially enhance the habitability of exoplanets around the star.

However, as a preprint, the paper is yet to be formally peer-reviewed by experts in the field.

"The paper of course involves a lot (a lot!) of arm waving. There is a lot involved, much more than the 'Goldilocks position' that would allow for liquid water to exist on a planet—a magnetosphere, plate tectonics, a 3rd-5th generation star, maybe even a moon to have tides, no tidal locking of the planet itself, and so on," Pieter Visscher, a marine sciences professor and one of the co-founders of NASA's Astrobiology Institute, told Newsweek.

"Life as we know it requires water, on the most basic level, energy generation, without which life is not possible, is based on aqueous biochemistry. But oxygen is not necessary at all. In fact, it is quite toxic and life has to adapt to its presence," he said.

This discovery may spur an increased focus on red-dwarf stars in terms of hunting for extra-terrestrial life in any form.

"Looking for biosignatures in exoplanets within the traditional habitable zone of their star is the starting point (and easiest way probably) to start looking for extra-terrestrial life, but it is not the only way," McKemmish said.

"A more complete approach (by harder to explain) is to just find out all you can about the atmospheres of exoplanets (molecular composition, temperature, etc), then try to create models to explain the observations by considering geology, physics and chemistry (e.g. volcanoes, meteorites, photochemistry, etc). If it can't be explained, then you can start to consider biology. (Biology in astrochemistry is often considered the hypothesis of last resort)."

Even if we do detect the signs of life on a far-off planet, there will be much disagreement about whether or not it was caused by living cells, according to McKemmish.

"There will be debates on the detection and then debates on the possible chemistry, geology, physics of the distant planet that will mean we don't know unambiguously that it is life," she said.

In the event that life was discovered on one of TRAPPIST-1's planets, at 40 light years away, our current space travel technology would take us around 800,000 years: even the small, uncrewed spacecraft New Horizons, which travels at 36,000 miles per hour, would take 80,000 years to reach our nearest stellar neighbors in the Centauri system a mere four light years away.

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