brightest stars near Earth, and what they found is rewriting the story of this fascinating system.
Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, researchers discovered that the ring isn’t shaped the way earlier models suggested.
Instead, it seems to have been sculpted long ago by unseen planets.
Debris disks like the one around Fomalhaut are huge belts of dust and rocky fragments, similar to our solar system’s asteroid belt, but much larger.
For nearly 20 years, scientists have puzzled over why Fomalhaut’s ring looks lopsided instead of forming a neat circle.
Now, new ALMA images show that the ring’s eccentricity—or how stretched out it appears—changes with distance from the star.
In earlier models, astronomers assumed the entire ring had the same level of eccentricity. But the new study shows the eccentricity decreases the farther out you go from the star.
This pattern, called a “negative eccentricity gradient,” has never been clearly seen before in any debris disk. Imagine Saturn’s rings, but instead of being centered neatly around the planet, the ring’s shape shifts as you move farther away.
Lead researcher Joshua Bennett Lovell from the Harvard-Smithsonian Center for Astrophysics explains: “Our observations show, for the first time, that the disk’s eccentricity isn’t constant. It steadily drops off with distance.”
This finding gives scientists an important clue: the warped shape may have been carved by a massive, hidden planet orbiting inside the ring.
According to the team’s models, such a planet could have influenced the debris during the star’s early history, more than 400 million years ago.
The disk’s unusual structure has likely been maintained ever since by the gravitational tug-of-war between the star and the unseen planet.
A second paper, led by Jay Chittidi at Johns Hopkins University, compared the new ALMA data with earlier images from the James Webb Space Telescope (JWST).
They found that the ring’s brightness and width could not be explained by older models that assumed a fixed eccentricity. The updated model finally matched the observations and gave researchers a clearer picture of how this system has evolved.
Scientists now hope that future ALMA observations will provide even more evidence—and perhaps direct hints—of the mysterious planet shaping Fomalhaut’s disk. To help the wider astronomy community, the team has shared their new modeling code so others can test it on different star systems.
In short, the warped ring around Fomalhaut may be the lingering fingerprint of ancient, still-hidden planets, offering a rare glimpse into how planetary systems—including our own—take shape and evolve.
Source: National Radio Astronomy Observatory.
