The James Webb Space Telescope has imaged the first asteroid belt found outside our solar system—and discovered it may hold evidence of hidden planets.
Astronomers focused the high-tech observatory on Fomalhaut, a nearby young star in a solar system that, though similar to ours, is much more chaotic. While other telescopes had previously photographed one ring around the star, Webb used its infrared capabilities to reveal two more rings nearer to Fomalhaut—a cosmic surprise for the researchers.
Each of the three rings is an asteroid belt—with space dust, asteroids and fragments of ruined planets—and the gaps between them are a strong indicator that as-yet undiscovered worlds could be shifting the debris with their gravity.
“Any time an astronomer sees a gap and rings in a disc, they say, ‘There could be an embedded planet shaping the rings,’” says Schuyler Wolff, a member of the study team and an astronomer at the University of Arizona, in a statement. “That structure is very exciting.”
Webb’s discovery of separate rings, published Monday in Nature Astronomy, has fueled hopes for finding planets around Fomalhaut. The nested rings of dust extend about 14 billion miles from the star—roughly 150 times the distance between Earth and the sun—and they’re much more complex than the familiar asteroid and Kuiper belts of our solar system.
“The belts around Fomalhaut are kind of a mystery novel: Where are the planets?” George Rieke, a team member and U.S. science lead for Webb’s Mid-Infrared Instrument (MIRI), says in the statement. “I think it’s not a very big leap to say there’s probably a really interesting planetary system around the star.”
Unfortunately, Webb’s Mid-Infrared Instrument (MIRI), which was used for this study, and its Near-Infrared Camera (NIRCam) can’t be much help in finding them: Any planets in Fomalhaut’s solar system would likely be too cold to be detected using infrared technology because of where the star is at in its life cycle.
“You could hide Jupiters in there, all over the place, and nobody would know,” Bruce Macintosh, director of the University of California Observatories who was not involved with the study, tells the New York Times’ Robin George Andrews. Only a planet several times bigger than Jupiter would be warm enough to be detectable.
The rings around Fomalhaut are not protoplanetary discs, or orbiting material that later comes together to create planets. Instead, these swirling fragments of past collisions are known as debris discs, which typically form once planets already exist in the system, notes Space.com’s Robert Lea.
“I would describe Fomalhaut as the archetype of debris discs found elsewhere in our galaxy, because it has components similar to those we have in our own planetary system,” lead author András Gáspár, an astronomer at the University of Arizona, says in the statement.
“By looking at the patterns in these rings, we can actually start to make a little sketch of what a planetary system ought to look like—if we could actually take a deep enough picture to see the suspected planets,” he adds.
Fomalhaut, known by professional and amateur astronomers alike for its big, bright presence in the southern hemisphere’s sky, is a relatively young star just 25 light-years from Earth. The star is only 440 million years old, compared to our sun’s 4.6 billion years. Yet, because they’re different types of stars, they’re both at around the same point in their life cycles—what scientists call middle aged.
But while our solar system is relatively calm, Fomalhaut appears to be going through a mid-life crisis, of sorts. Life in that solar system would be “chaotic as hell,” Macintosh tells the Times. “If there are planets there, they’re getting smacked around by asteroids all the time.”
The James Webb Space Telescope, which was created through a collaboration between NASA, the European Space Agency and the Canadian Space Agency, is the largest and most powerful space-based observatory ever built. Since its launch in 2021, the $10 billion telescope has taken a plethora of stunning images of outer space and provided scientists with an avalanche of new data, from imaging exoplanets to detecting the most distant galaxy ever seen.