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NASA/JPL-Caltech
An artist's concept of the view from one of TRAPPIST-1's planets, looking toward the star and some of the system's other planets.

Editor's note: This is based on a post on the author's website.

It would be hard to overestimate the importance of NASA’s latest exoplanet discovery, but I did.

On Feb. 20, a news release from the Jet Propulsion Laboratory in Pasadena, California, notified the world that a major announcement about planets around other stars was going to be announced on live TV on Feb. 22.

Announcements about new exoplanets have become routine. Since the first discovery in January 1992, the Kepler Space Telescope alone has discovered more than 2,300 confirmed exoplanets, and another 4,600-plus planet candidates are awaiting proof, according to nasa.gov.

Let’s review what was known about exoplanets before Feb. 22, by checking NASA’s Exoplanet Exploration timeline at exoplanets.nasa.gov.

• In 1999, the first multiplanet system was found. According to exoplanets.nasa.gov, "Researchers from San Francisco State University and the Harvard-Smithsonian Centers, working independently, announce the discovery of two additional planets orbiting the star Upsilon Andromeda in the constellation Pegasus."

• 2001 brought a different kind of space odyssey: the announcement of the first exoplanet within a star's "habitable zone," the region where the planet is neither too cold nor too hot for liquid water to remain on the surface.

• Later that year, scientists David Charbonneau and Timothy Brown used a spectrometer on the Hubble Space Telescope to analyze the atmosphere of an exoplanet. According to exoplanets.nasa.gov, "Future atmospheric observations may help scientist determine if a planet can, or does, harbor life."

• In July 2015, NASA announced the discovery of Kepler-452b, a planet 1.6 times the size of Earth orbiting in the habitable zone of a G-type (sun-like) star 1,400 light-years away in the constellation Cygnus. A year on this planet lasts 385 days. Jon Jenkins, analyst at Ames Research Center, Moffett Field, California, said in the announcement of this system, "It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."

So when NASA intimated recently that something was up, something big, what could I think? Multiple planets, done this; habitable zone planets, done that; analyze atmosphere, yes; near-Earth-size, habitable-zone planet around a sun-like star, check.

Thought I, "It must be what we’ve been waiting for: proof of alien life."

No.

The presentation was dramatic, broadcast live over NASA TV. I watched on my iPhone and was disappointed.

Really, though, it was a wonderful achievement.

The Spitzer Space Telescope, which records infrared images, had evidence of the first star system with seven Earth-sized planets, three of which are believed to be in the habitable zone. The star is called TRAPPIST-1, named for the acronym of the European Southern Observatory telescope in Chile that had discovered three planets in the system, according to eso.org.

It’s not the niftiest acronym: TRAnsiting Planets and PlanetesImals Small Telescope–South. TRAPPIST-1 is around 40 light-years away in the constellation Aquarius, NASA says. That amounts to 235 trillion miles, which is "relatively close to us."

(This led to a funny error on the part of the online news site Mashable on Feb. 26: "The entire internet is still buzzing about the discovery of seven Earth-sized planets in a 'nearby' star system — it's only about 40 light-years, or 235 million miles, away. In galactic terms, that's pretty much right next door." Seven new Earth-size planets only 235 million miles away — much closer than Jupiter! How could we have overlooked them so long?)

As NASA’s press release on Feb. 22 said, TRAPPIST-1 is a small, ultra-cool (temperature-wise) star. The habitable zone, consequently, is near the star. The seven planets are so close together that if observers were on one of them, "they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth's sky."

"Habitable zone" may be a misnomer in this situation. The closeness to the star could make life impossible. Scientists think the planets might be tidally locked to the star, as the moon is to Earth, with one side always facing the larger object. Maybe one side of each planet would be roasted and the other frozen. Temperature differences might whip up monstrous winds howling across the planet. The extreme proximity may expose the planets to killing radiation from the star.

After next year’s launch of the James Webb Space Telescope, assuming all goes well, scientists should be able to get a good idea about the atmospheres of some of these planets, according to the news release. If life exists there, the telescope's instruments may be able to sniff out its markers. For example, free oxygen, released by plants, doesn’t hang around long in Earth's atmosphere before it combines with something else. Detection of this element might indicate life is continuously releasing it into an exoplanet’s atmosphere.

"With much greater sensitivity, Webb will be able to detect the chemical fingerprints of water, methane, oxygen, ozone and other components of a planet's atmosphere," according to the release. "Webb also will analyze planets' temperatures and surface pressures — key factors in assessing their habitability.”

2 comments on this story

Because of what seems to me to be nearly insurmountable obstacles to life around TRAPPIST-1, I’m not tingling with anticipation. A better candidate would be some Earth-like planet orbiting a sun-like star in the right zone, such as the exoplanet Kepler-452b. If one is found only a few dozen light-years away, probably its atmosphere could be characterized.

Until then, I’ll try not to overestimate the value of NASA pronouncements.

Joe Bauman writes an astronomy blog at the-nightly-news.com and is the vice president of the Salt Lake Astronomical Society, which meets the third Wednesday of each month except December and online at slas.us. His email is joe@the-nightly-news.com.