Discovery of Seven Earth-Sized Exoplanets Orbiting a Distant Star Could Support Life
TL;DR
A study has revealed that the TRAPPIST-1 system hosts seven Earth-sized planets, three of which reside in the “Goldilocks Zone” where liquid water—and possibly life—could exist. Using advanced telescopes, including NASA’s Spitzer and ESO’s Very Large Telescope, researchers discovered these exoplanets around an ultracool dwarf star just 39 light-years away. These planets offer the most promising targets for future life searches, with the upcoming James Webb Space Telescope expected to provide critical data on their atmospheres and potential habitability.
“The planets also are very close to each other. If a person was standing on one of the planet’s surface, 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. That would be incredible to witness.” Don’t forget to discuss this topic below in the comment section!
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The most promising location for finding life beyond our solar system has just become even more appealing.
Researchers using the ESO’s TRAPPIST telescope (Transiting Planets and Planetesimals Small Telescope) discovered three planets orbiting a small, faint red dwarf star located 39 light-years away. All three exoplanets are roughly Earth-sized and situated in the “Goldilocks Zone,” where temperatures range between 0 and 100 degrees Celsius—ideal for liquid water and possibly life.
The team, led by Michaël Gillon from the STAR Institute at the University of Liège in Belgium, then used additional telescopes, including NASA’s Spitzer Space Telescope and ESO’s Very Large Telescope, to study the system further. A paper published in Nature reveals that the TRAPPIST-1 system doesn’t just have three Earth-sized planets, but seven, six of which are likely rocky and all of which could potentially support liquid water.
“These planets are the most promising targets to search for life over the next decade, and it’s incredible that they all transit the same star,” said co-author Julien de Wit, a planetary scientist at MIT, in an email to Popular Mechanics. “This means we can study each one in great detail, offering a comprehensive view of a planetary system unlike ours.”
A Solar System Reminiscent of Jupiter’s Moons
TRAPPIST-1 is classified as an ultracool dwarf star. This dim star has only 8% of the Sun’s mass, with a temperature of 2,550 Kelvin compared to 3,800 Kelvin for other red dwarfs and 5,800 Kelvin for our Sun. TRAPPIST-1 is only slightly larger than Jupiter.
Fortunately, the seven planets around TRAPPIST-1 orbit far closer to their star than we do to ours. The inner planets’ orbits resemble those of Jupiter’s Galilean moons. All seven planets orbit TRAPPIST-1 much closer than Mercury orbits the Sun, receiving about the same energy and warmth as Earth.
As the planets orbit, they also pass close to one another. NASA notes that “if a person stood on one of these planets, they might be able to see geological features or clouds of neighboring worlds, which could sometimes appear larger than the Moon does in our sky.”
Some planets are in a better position to support liquid water than others. The star is named TRAPPIST-1A, and the planets, from the closest to the farthest, are labeled 1b, 1c, 1d, 1e, 1f, 1g, and 1h. TRAPPIST-1b, 1c, and 1d are likely too close and too hot for water, while TRAPPIST-1h may be too distant and cold. However, TRAPPIST-1e, 1f, and 1g are in the optimal “Goldilocks Zone”—potentially ideal for life, though we know very little about them yet. These planets could host oceans or forests. (Okay, maybe not forests, but it’s not impossible.)
We currently know very little about these planets beyond estimates of their size, distance from the star, and orbital periods. Exoplanets are detected when they transit in front of their host star, causing a small dip in brightness that we can measure. From these changes in brightness, we can infer the presence of planets and their sizes.
Red dwarfs, like TRAPPIST-1, are ideal for this type of search because they are naturally dim, making any dips in brightness more noticeable. Planets orbiting such stars also tend to have shorter orbits, sometimes completing a full trip around their star in mere days or weeks, giving researchers more opportunities to observe transits. (The TRAPPIST-1 planets complete their orbits in as little as 1.5 days and up to 20 days.)
Red dwarfs are the most common and long-lived stars in the galaxy. Around 85% of the 100 billion stars in the Milky Way are red dwarfs. TRAPPIST-1 will continue burning hydrogen for another 10 trillion years—about 700 times longer than the universe’s entire history—allowing ample time for life to potentially evolve.
Despite their promise, these planets have characteristics that could affect their habitability. One concern is that the planets might be tidally locked with TRAPPIST-1, meaning one side always faces the star in perpetual daylight, while the other remains in constant darkness.
Another issue is that red dwarfs tend to be highly active stars, producing flares, eruptions, and coronal mass ejections that bombard nearby planets with radiation. A study raised doubts about the habitability of Proxima b, the closest exoplanet to Earth, for this reason. However, TRAPPIST-1 is cooler than Proxima Centauri and may not emit as many high-energy particles. “To the best of our knowledge, TRAPPIST-1 seems particularly quiet,” says de Wit.
TRAPPIST-1 might be a peaceful, life-sustaining star after all. But since it’s almost 40 light-years away and incredibly faint, how can we know for sure?
Exploring Exoplanet Atmospheres
A project is in development to send small probes to the Alpha Centauri system, our nearest stars, as part of the Breakthrough Starshot initiative. By using Earth-based lasers to continuously hit reflective surfaces on the probes, they could be accelerated to about 20% of the speed of light. This photonic propulsion technology could allow us to reach Alpha Centauri in 20 to 30 years.
But we won’t be reaching TRAPPIST-1 any time soon, as it is eight times farther than Alpha Centauri. Even if a probe could travel at relativistic speeds, it would still take two centuries to arrive, and sending a signal back from 40 light-years away would be nearly impossible. For now, we’ll need to rely on studying TRAPPIST-1 from Earth.
We can still learn a lot with current and upcoming telescopes, especially in the 2020s. By analyzing light passing through an exoplanet’s atmosphere, we can detect gaps in the spectrum—specific wavelengths of light absorbed by certain elements. This technique, known as absorption spectroscopy, allows us to determine the atmospheric composition of planets, even those 40 light-years away. “There is a lot we can do with what we already have and with what’s coming soon,” de Wit said, referring to telescopes. “In observations of this system made with Hubble last May, we’ve already ruled out the presence of puffy, hydrogen-rich atmospheres around the two innermost planets, meaning they are not ‘mini-Neptunes’ and are likely rocky like Mercury, Venus, Earth, or Mars.”
The upcoming launch of the James Webb Space Telescope (JWST) and the completion of the Giant Magellan Telescope (GMT) in Chile will offer clearer views of these exoplanets. The James Webb’s 18 gold-coated mirrors will allow it to detect objects 16 times fainter than Hubble, while the GMT’s seven massive mirrors could enable direct imaging of exoplanets. These tools, along with others like the European Extremely Large Telescope, will help us determine the nature of the TRAPPIST-1 planets’ atmospheres.
“In the next two years, we hope to use Hubble to search for water or methane-based atmospheres,” de Wit said. “In the future, the James Webb Space Telescope will help us analyze the planets’ atmospheric composition, temperature, and pressure—key details to understanding their surface conditions.”
While this won’t confirm life, it could provide strong evidence if one of these planets does support it. Astronomers will be looking for “biosignatures,” such as high oxygen levels that could indicate photosynthesis. However, abundant oxygen alone doesn’t guarantee the presence of life. “We need more than just O2,” says de Wit. “Biosignatures can include complex molecules like CFCs (chlorofluorocarbons) or a combination of molecules like H2O, O2/O3, CO2, or CH4. While the JWST may not give us definitive proof of life, it will tell us a lot about the planets’ habitability.”
Though we won’t be sending probes to TRAPPIST-1 anytime soon, its relative proximity on a galactic scale is still fascinating. With planets orbiting their star in just days, we’ll have hundreds of chances to observe them with increasingly sophisticated telescopes. Many astronomers believe that TRAPPIST-1 is not an anomaly, and that many nearby red dwarfs may have similar planetary systems.
It’s hard not to wonder if one of those planets harbors alien life—and with continuing research, we might soon find out.
Spitzer detects 7 earth size planets around the TRAPPIST-1 Star System
40 light years away
3 planets are in the right zone for liquid water
Have measured the masses and radi of earth-size planets
Can look at atmosphere and bio-signatures
Planets are close to each other, you would see them similarly as you would see Earth’s moon.
Planets are so close, they interact gravitationally on each other.
Trappist-1e is very close in size to earth. It receives a similar amount of light as Earth does.
Trappist-1f (MIGHT) be water-rich and similar in size as earth (NASA just said currently no detection of water). Receives about as much light as Mars.
10)Trappist-1g is largest in the system, 13% larger radius than Earth. Receives about as much light as Mars and the Asteroid belt.
They also said that one of these planets has the initial signature of being a water rich environment.
Whatever secrets it may harbor, the TRAPPIST-1 system will surely be a sight to behold. Though the star is small, its nearness to the planets means that, from their perspective, it appears about three times as large as our sun. The outermost planets enjoy the daily spectacle of their neighbors passing across the sky and in front of their shared sun, each world a large dark spot silhouetted against the salmon-colored star. Its dim glow, which skews toward the red and infrared end of the light spectrum, bathes the planets in warmth and paints their skies with the crimson hues of a perpetual sunset.
Space can be really beautiful.
This is exciting, because I feel like I’m always reading about earth-like planets, but they always seem to be 500 thousand light years away, but 40 sounds really close and obtainable
Voyager 1, the farthest any man made object has travelled and the fastest has only travelled a mere 19 light hours IIRC… As close as 40 light years is compared to other planets, it’ll be essentially forever until we can get there
Due to its mass, the star has the ability to live for up to 4–5 trillion years, meaning that TRAPPIST-1 may be one of the few remaining low-mass main sequence stars when the Universe is much older than it is now, and when the gas needed to make stars will have been used up.
The future of our race, folks. This is where we go when the sun dies.
7 potentially habitable planets around one star, 3 of which are under the right conditions to contain liquid water? Incredible.