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Scientists discover seven ‘habitable-zone’ planets

Credit: Courtesy photoIMPORTANT FIND: The discovery of seven potentially habitable planets in the same solar system, Trappist-1, was announced yesterday. Scientists at MIT are studying the planets’ atmospheres to see if they could support life.

Seven newly found habitable-zone planets orbiting a single star just 39 light years from Earth are the best targets so far, scientists say, in the search for extraterrestrial life.

The astonishing find, published yesterday in the journal Nature, marks a new record for the largest known number of planets orbiting a single star within the zone where life is possible, outside our solar system.

“This is the first time that we’ve found so many small planets — each potentially habitable — around the same star, a star that’s close to us,” said Julien de Wit, a planetary scientist at Massachusetts Institute of Technology, who is studying the planets’ atmospheres for crucial clues to whether these new worlds could harbor life.

The planets circle a dim “dwarf” star called Trappist-1, barely the size of Jupiter. Three are in the so-called habitable zone, the area around a star where liquid water — and possibly life — might exist; the others are right on the edge.

“I absolutely think it’s interesting to know where are there other worlds that we someday might travel to,” said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics, who is not involved in the study. “It’s important for humanity to live on multiple planets because right now, if you lose the Earth, you lose the whole human species — and not just humanity, but terrestrial life.”

Scientists said they need to study the planets’ atmospheres to determine whether these rocky, terrestrial planets could support some sort of life. But their discovery already hints at just how many Earth-size planets could be out there — especially in a star’s sweet spot, ripe for extraterrestrial life. The more planets like this, scientists say, the greater the potential of finding one that’s truly habitable.

“For thousands of years, we wondered if we were alone in the universe,” said David Charbonneau, a Harvard professor of astronomy. “So it’s exciting to know that we’re alive in a generation when we might be able to look for life on other planets.”

Last spring, Michael Gillon of the University of Liege in Belgium and his team reported finding three planets around Trappist-1. Now the count is up to seven, and Gillon said there could be more.

This solar system 235 trillion miles away is so compact that if the tiny, cold star at its center were our sun, all seven planets would be inside the orbit of Mercury, the innermost planet of our own solar system.

Trappist-1 would shine 200 times dimmer than our sun, however, a kind of perpetual twilight. And the star would glow red or salmon-colored, the researchers speculate.

Using both ground and space telescopes, Gillon and his team spotted and tracked the planets around it, as each of them cast shadows on the star while passing in front of it.

All seven look to be solid like Earth — mostly rocky and possibly icy, too. But life could still exist on them, the researchers said.

“Here, if life managed to thrive and releases gases similar to that which we have on Earth, then we will know,” said the University of Cambridge’s Amaury Triaud, one of the researchers.

Chemical analyses should indicate life with about 99 percent confidence, Gillon said, but “we will never be completely sure” without going there.

Herald wire services contributed to this report.