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These Earth-like planets may be better than Proxima b to look for E.T.

They're 10 times farther away than the closest possible exoplanet, but a trio of Earth-size planets might actually be the best candidates so far in the search for life beyond our solar system.

Last month, the world freaked out -- and justifiably so -- over the news that the nearest star to the sun is orbited by an Earth-like planet. But on Tuesday, a group of scientists quietly published a paper that could offer a much bigger boost to the prospect of finding life beyond our solar system sooner rather than later.

Astronomers used a very high-resolution camera along with the 8-meter Gemini South telescope in Chile to essentially double-check and seal the deal on a big discovery earlier this year. There are three Earth-size planets, including one in the habitable zone, around a cool dwarf star relatively nearby.

As we reported in May, this is a big deal not just because there are three possible Earth cousins around a single star, Trappist-1, but because they are the first such cool dwarf orbiters detected.


An artist's rendition of how the Trappist-1 system might look


"Why are we trying to detect Earth-like planets around the smallest and coolest stars in the solar neighborhood?" lead researcher Michaël Gillon said in a statement at the time. "The reason is simple: Systems around these tiny stars are the only places where we can detect life on an Earth-sized exoplanet with our current technology. So if we want to find life elsewhere in the Universe, this is where we should start to look."

Steve Howell of NASA's Ames Research Center led the new round of observations that rule out the possibility another nearby dwarf star is complicating the data and confirm the presence of at least one possibly habitable planet around a close neighbor star. The findings were published Tuesday in Astrophysical Journal Letters.

"This system is also going to be a very good target for many detailed follow-up efforts, especially those attempting to characterize the atmosphere of a rocky exoplanet," Howell told me. "I would assume that the James Webb Space Telescope will target this system and work to get transit spectroscopy of the planets, particularly the habitable zone one."

Transit spectroscopy is a technique astronomers use to detect elements like oxygen and methane in the atmosphere of a planet that might indicate life is present.

Trappist-1 and the planets around it are roughly 10 times farther away from the sun than Proxima Centauri and its earth-like planet, Proxima b, that generated so much attention last month. Still, that's very close on the galactic scale. The fact that Trappist-1's planets were detected via the transit method is a really big deal because it means that spectroscopy can potentially be performed.

When I spoke to astronomers in advance of the announcement of Proxima b, I was surprised to find their enthusiasm was a little bit tempered. That's because no one has yet been able to observe that closest possible exoplanet passing in front of, or transiting, its dwarf star, Proxima Centauri.

"I can't imagine dreaming up a better habitable planet...with one key caveat. Proxima b likely doesn't transit," Harvard astronomy professor David Charbonneau told me in an email about Proxima b last month. "I bet there is a planet just like Proxima b that transits a nearby star. The star might be 8 or 10 parsecs away, but I'll take that trade."

The Trappist-1 system looks to provide exactly that trade, give or take a couple of parsecs.

We might not see a nanocraft like those Stephen Hawking and Yuri Milner's Breakthrough Starshot project want to send to Proxima b reach the Trappist-1 system in our lifetimes. That journey would take 200 years. But it's possible we'll find evidence of life on the more distant Trappist planets long before we spy anything nearly so interesting on Proxima b.

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