7 Earth-size worlds found orbiting star; could hold life

7 Earth-size worlds found orbiting star; could hold life
This illustration provided by NASA/JPL-Caltech shows an artist's conception of what the TRAPPIST-1 planetary system may look like, based on available data about their diameters, masses and distances from the host star. The planets circle tightly around a dim dwarf star called Trappist-1, barely the size of Jupiter. Three are in the so-called habitable zone, where liquid water and, possibly life, might exist. The others are right on the doorstep. (NASA/JPL-Caltech via AP)

For the first time, astronomers have discovered seven Earth-size planets orbiting a single nearby star—and these new worlds could hold life.

This cluster of planets is less than 40 light-years away in the constellation Aquarius, according to NASA and the Belgian-led research team who announced the discovery Wednesday.

The planets circle tightly around 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 water and, possibly life, might exist. The others are right on the doorstep.

Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life. But it already shows 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, the greater the potential of finding one that's truly habitable. Until now, only two or three Earth-size planets had been spotted around a star. A rocky Earth-sized world inside a star's habitable zone is considered the best candidate for finding evidence of life.

"We've made a crucial step toward finding if there is life out there," said the University of Cambridge's Amaury Triaud, one of the researchers.

The potential for more Earth-size planets in our Milky Way galaxy is mind-boggling. The history of planet-searching shows "when there's one, there's more," said Massachusetts Institute of Technology astrophysicist Sara Seager.

"With this amazing system, we know that there must be many more potentially life-bearing worlds out there just waiting to be found," she said.

NASA's Thomas Zurbuchen, associate administrator for the science mission, said the discovery "gives us a hint that finding a second Earth is not just a matter of if, but when," and addresses the age-old question of "Are we alone out there?"

"We're making a step forward with this, a leap forward in fact, toward answering that question," Zurbuchen said at a news conference.

Last spring, the University of Liege's Michael Gillon and his team reported finding three planets around Trappist-1. Now the count is up to seven, and Gillon said there could be more. Their latest findings appear in the journal Nature.

This crowded yet compact solar system—235 trillion miles away—is reminiscent of Jupiter and its Galilean moons, according to the researchers.

Picture this: If Trappist-1 were our sun, all seven planets would be inside Mercury's orbit. Mercury is the innermost planet of our own solar system.

7 Earth-size worlds found orbiting star; could hold life
This image provided by NASA/JPL-Caltech shows an artist's conception of what the surface of the exoplanet TRAPPIST-1f may look like, based on available data about its diameter, mass and distances from the host star. The planets circle tightly around a dim dwarf star called Trappist-1, barely the size of Jupiter. Three are in the so-called habitable zone, where liquid water and, possibly life, might exist. The others are right on the doorstep. (NASA/JPL-Caltech via AP)

The ultracool star at the heart of this system would shine 200 times dimmer than our sun, a perpetual twilight as we know it. And the star would glow red—maybe salmon-colored, the researchers speculate.

"The spectacle would be beautiful because every now and then, you would see another planet, maybe about as big as twice the moon in the sky, depending on which planet you're on and which planet you look at," Triaud said Tuesday in a teleconference with reporters.

Years are exceedingly short in this star system—the planets take just 1 ½ to 20 days to orbit Trappist-1.

The Leiden Observatory's Ignas Snellen, who was not involved in the study, is excited by the prospect of learning more about what he calls "the seven sisters of planet Earth." In a companion article in Nature, he said Gillon's team could have been lucky in nabbing so many in one stellar swoop.

"But finding seven transiting Earth-sized planets in such a small sample suggests that the solar system with its four (sub-) Earth-sized planets might be nothing out of the ordinary," Snellen wrote.

Altogether, astronomers have confirmed close to 3,600 planets outside our solar system since the 1990s, but barely four dozen are in the potential of their stars, and of those, just 18 are approximately the size of Earth.

Gillon and his team used both ground and space telescopes to identify and track the seven Trappist-1 planets, which they label simply by lowercase letters, "b'' through "h." As is typical in these cases, the letter "A''—in upper case—is reserved for the star. Planets cast shadows on their star as they pass in front of it; that's how the scientists spotted them.

Tiny, cold stars like Trappist-1 were long shunned by exoplanet-hunters (exoplanets are those outside our ). But the Belgian astronomers decided to seek them out, building a telescope in Chile to observe 60 of the closest ultracool dwarf . Their Trappist telescope lent its name to this star.

While faint, the Trappist-1 star is close by cosmic standards, allowing astronomers to study the atmospheres of its seven temperate . All seven look to be solid like Earth—mostly rocky and possibly icy, too.

They all appear to be tidally locked, which means the same side continually faces the star, just like the same side of our moon always faces us. Life could still exist at these places, the researchers explained.

"Here, if life managed to thrive and releases gases similar to that that we have on Earth, then we will know," Triaud said.

Chemical analyses should indicate life with perhaps 99 percent confidence, Gillon noted. But he added: "We will never be completely sure" without going there.

Explore further

Temperate earth-sized worlds found in extraordinarily rich planetary system (Update)

Journal information: Nature

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Feb 23, 2017
d, e, and f probably could prove habitable, maybe even g given a truly massive greenhouse effect. The concern with such a low mass red dwarf is the propensity for flaring, which could blast off any atmosphere early in the star's development. That said, still pretty cool. Hopefully we'll keep finding more systems like this.

Feb 23, 2017
Red Dwarfs are well known for their abundance of sunspots causing them to dim. Sunspots were often mistaken for planets in transit in early astronomy. Regardless the chances of these purported planets supporting life is slim as red dwarfs emit light in the infra red and not the visible spectrum necessary to life on earth.

Feb 23, 2017
I think the real point with all the exoplanet discoveries is that the chances are that sometime we will find a planet very similar to Earth and is spurring more research and that can't be a bad thing.

Feb 23, 2017
Fulfillment of an old rock song. Too bad the author(s) had no idea of how his work would come true.....: "T'is the Dawning of the Age..of Aquarius!.." This WILL generate a space race like no other. We will have NO choice but to participate, and naysayers will doubt at their peril. With the survival of humanity at stake, Physicist Steven Hawking's words about us needing a new planetary home will stand four square behind the new majority of humanity clamoring for progress.

Feb 24, 2017
I used to keep some 'outside plants' in our basement in Michigan in the winter time. Michigan winters are SEVERE!! One year it did not get above zero for over a hundred days. One 18December2004 I think, it snowed over a meter in one nite....39 inches and not in drifts. The drifts were some 20 feet deep in gullies. To keep them alive, I first tried ultraviolet lights cuz' I had heard that all the wackky week growers used those. No dice. Plants were dying in our ultraviolet fluorescent lites. When I tried the infrared fluorescent lites though, it was like the plants singing: "Happy Days are Here Again...O Happy day -ay -ays!

So do not tell me that infrared light does not grow plants. Betcha those worlds grow plants, and if plants then too the animals too for plants are food for animals, among other things if you are a goat or a bear.

Feb 24, 2017
After they found the microbes in a crystal in a mexican mine
I'm more of the opinion that could find life anywhere but gas giants (and I wouldn't even rule that one out completely).

Reducing the search for potentially life-bearing worlds to filtering by surface conditions seems needlessly limiting.

(And no: none of these worlds - even if water bearing - are 'human habitable' without major terraforming)

Mar 03, 2017
Steven Hawking pondered the relative chances of life on other planets. We have found life in volcanic undersea vents in conditions similar to the surface of Venus but for the humidity....temperatures in excess of 600 degrees C. at thousands of atmospheres of pressure in a highly acidic/basic local environment. We have found life, lithophilic microbes underground at hight temperatures and pressures in the presence of toxic gases under similar pressure (South African study). Point is as one physicist said, if something can occur, it will occur, and it will an infinite number of times. Life is more plentiful than grains of sand in the Sahara. We have found it thrives in the cold of space. Our oldest fossils...no not trump....placed life in Archaean Era rocks less than half a billion years after the purported origin of the Earth. Course how many millenia passed during the formation of the Earth from the agglutination of rocks to the Earth protocore. Life on every rock?

Mar 03, 2017
The orbital periods of those planets are much more like those of moons around a planet.

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