The inner ring is analogous to our asteroid belt, while the outer ring is similar to the sun’s Kuiper belt. But Fomalhaut also has an intermediate scree road between the two, most likely a mix of icy and rocky ephemeral.
The solar system lacks this superstructure, “partly because we have these big honking planets in the middle” — Jupiter, Saturn, Uranus and Neptune — “that cleared things up,” he said. Bruce Macintoshthe director of the University of California Observatories, who was not involved in the study.
The gap between Fomalhaut’s inner and intermediate rings may have been carved by a planet. But there was no direct evidence of any world to be seen. At this point in Fomalhaut’s life cycle, most of the planets would have cooled and only one planet, many times larger than Jupiter, would still be hot enough to be detected by the Webb’s infrared instrument.
“You could hide Jupiters all over there, and no one would know,” said Dr. Macintosh.
The intermediate belt is also where exoplanet hunters once thought they had seen a world they called Fomalhaut b. But in 2020, Dr. Gaspar and his colleagues suggest that what other scientists once thought was an intact exoplanet was in fact an expanding cloud of debris created by an epic collision.
One problem with this idea was that this part of space seemed empty, so it seemed unlikely that two objects would have managed to collide. The team’s discovery of the intermediate debris belt has now provided a solution.
“We now know there’s stuff there,” said Dr. Christiansen of the NASA Archives. “OK, so it’s a collision — we can finally put that to bed.”
Cataclysmic melees don’t just happen near the star. What appears to be a massive maelstrom of dust in the outer belt may be the ghost of another giant impact.
“That’s just cool,” said Dr. Christensen. “What is it? It’s very tempting.”
Astronomers are delighted that the Webb telescope is providing a front row seat to the drama of this star. It also makes them appreciate the relatively calm nature of the solar system. Fomalhaut would be “damned chaotic,” said Dr. Macintosh, adding, “If there are planets out there, they’re being knocked around by asteroids all the time.”