3 Earth-like planets found in ‘habitable zone’

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CREDIT: Handout image by ESO -- M. Kornmesser

It’s a staple of science fiction: A city-size starship leaves our solar system, its passengers propagate on a trip that spans multiple generations and settle a planet several light-years from home. Alpa Centauri, the nearest star system, is often featured in these stories. Kim Stanley Robinson made Tau Ceti, nearly three times as far away, the destination for a generation ship in his 2015 novel, Aurora, because he thought the system was more likely to have a habitable environment.

Life may not imitate art in this case, but they do kind of orbit each other. A team of international scientists, including a NASA researcher, has identified three Earth-size planets that might be candidates if real-life future humans ever set out to reach an habitable exoplanet, or worlds orbiting other stars.

The newly discovered system, announced in Nature on Monday, is about 40 light-years from Earth. That’s close enough, astronomically speaking, to be considered “nearby.” Our local galactic neighborhood might include the 3,000 or so nearest stars, says Michaël Gillon, an astronomer at Belgium’s University of Liège and the paper’s lead author. “So 100 parsecs”-more than 325 light years-“is still pretty nearby at the galactic scale.”

The planet hunters were looking for so-called ultracool dwarf stars, which are too weak to show up in the usual searches for exoplanets. They came across two Earth-size planets that take just two days to zip around their Jupiter-scale dwarf star. The planets receive about two to four times our solar radiation, and virtually none of it is in the visible spectrum. The sun is probably too close for the planets to be entirely habitable, but the authors suggest there might spots where humans could survive. The planets are tidally locked to their star, just as the moon is to Earth, meaning the same side always faces the light.

Researchers caught a third planet transiting the dwarf star but didn’t have enough information to characterize it as well as the other two. Astronomers hunt planets by measuring changes in the brightness when something passes between a star and Earth. For this project the scientist used the “Transiting Planets and Planetesimals Small Telescope,” abbreviated as Trappist. Yes, Gillon explains, the acronym was picked for a reason: “Except for a few monks, the word ‘Trappist’ in Belgium calls to mind excellent beers.”

Gillon and his colleagues will need help from the Hubble Space Telescope and the James Webb Space Telescope to reveal what’s really in the atmospheres of these newly found planets. It’s certainly too soon to build a Noah’s space ark-but it’s never too early to think about it. This type of speculation isn’t exclusively the domain of science fiction. When NASA discovers an enticing planet, it often asks artists to go to work on a geoscience-guided mock-up.

(c) 2016, Bloomberg · Eric Roston

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