Recent observations from NASA’s Hubble Space Telescope are challenging long-held assumptions about planetary systems, revealing evidence of ongoing and dramatic cosmic collisions. Astronomers have detected a second, recent impact within the debris disk surrounding the star Fomalhaut, located 25 light-years away, suggesting such events may be more common than previously thought. The findings offer a rare glimpse into the violent processes that shape planetary development and could help explain the evolution of systems both near and far.
NASA’s Hubble Space Telescope has uncovered new evidence around a nearby star that supports the theory that a previously observed object wasn’t a planet, but the result of a massive cosmic collision.
Astronomers spotted a faint new point of light near the inner edge of the extensive dust ring surrounding the star Fomalhaut in 2023. This object closely resembles a previous detection from the mid-2000s, which gradually faded over time.
Both objects appeared in a location consistent with scientists’ predictions for debris created by a high-speed impact between large planetesimals – early building blocks of planets beyond our solar system.
Capturing such a rare event is described as “remarkable” by Paul Kalas, the lead researcher from the University of California, Berkeley.
Together, the two detections provide direct evidence that large cosmic collisions are still occurring in mature planetary systems. Understanding these collisions is crucial to understanding how planetary systems evolve over time.
By observing this impact almost in real-time, scientists can estimate how frequently such collisions occur, how much material is released, and how debris disks – and the planets that may form from them – continue to evolve long after a star is born.
“This is the first time I’ve seen a point of light just appear in an extrasolar planetary system,” said Kalas in a statement.
“This object wasn’t present in any previous Hubble images, meaning we just witnessed a massive collision between two objects and the formation of a huge debris cloud unlike anything we’ve seen in our own solar system.”
Fomalhaut is located approximately 25 light-years from Earth in the Piscis Austrinus, or Southern Fish, constellation and is one of the brightest stars in the night sky.
The star is surrounded by multiple dust and debris belts, leftover material from the planet formation process, similar to the Kuiper Belt beyond Neptune in our solar system.
In 2004, Hubble detected a compact light source within the belt, later named Fomalhaut b. At the time, scientists debated whether the object was a planet shrouded in dust or something else entirely.
By 2008, some researchers even believed it could be the first extrasolar planet discovered using visible-light telescopes.
However, as time passed, the object’s behavior raised doubts. The mysterious source dimmed instead of brightening, appeared to stretch out, and eventually disappeared.
These changes were more consistent with the characteristics of a debris cloud formed when two large bodies collided and slowly dispersed.
When astronomers revisited the system nearly 20 years later, the original object was no longer visible.
Instead, they observed a new source near the same dust ring, indicating a second major collision had occurred in roughly the same region. The research was published in the journal Science.
“What we’ve learned,” Kalas said, “is that large dust clouds can masquerade as planets for years.”
Notably, the research team found the two debris clouds were relatively close together. If the collisions were random, experts would expect the locations to be more widely scattered.
Researchers are also puzzled by the fact that two major collisions occurred within a relatively short timeframe. Previous theories suggested events of this magnitude should only happen once every 100,000 years.
“If you had a movie of the last 3,000 years and you fast-forwarded it so that each year lasted just a fraction of a second, imagine how many flashes of light you’d see,” Kalas explained. “The Fomalhaut planetary system would appear to sparkle with these collisions.”
The dust clouds are visible because they reflect starlight, allowing telescopes like Hubble to detect them.
However, the same starlight also pushes the small dust grains outward, causing the clouds to spread and fade. This process explains why the first cloud disappeared and why the second cloud is also likely to fade over time.
Based on the brightness of the debris, researchers estimate the colliding objects were approximately 60 kilometers (37 miles) wide, larger than most asteroids involved in known collisions within our solar system.
Such impacts release vast amounts of dust, temporarily making the normally invisible event bright.
For astronomers, this discovery provides a rare opportunity to witness firsthand the destructive events that once shaped – and may still be shaping – planetary systems throughout the galaxy, according to Mark Wyatt, a co-author of the study from the University of Cambridge, England.
The research team anticipates further insights from the James Webb Space Telescope, which observes the universe in infrared light, to reveal the size and composition of the dust.
“This system is a natural laboratory for studying how planetesimals behave when they collide,” Wyatt stated, “which ultimately tells us about what they’re made of and how they formed.”
