NASA’s Hubble Space Telescope has unveiled fresh evidence surrounding a neighboring star indicating that an object previously observed was not a planet but rather the result of a significant cosmic collision. In 2023, astronomers identified a dim light near the inner edge of a dust ring encircling Fomalhaut, reminiscent of an earlier observation from the mid-2000s that eventually diminished. Both objects manifested in a region where scientists anticipate debris from fast-paced collisions between substantial planetesimals, the foundational rocky components of exoplanets. Capturing such an occurrence is “incredible,” stated Paul Kalas, the leading investigator from UC Berkeley.

These discoveries offer direct proof that significant cosmic collisions continue to transpire within established planetary systems. By monitoring these impacts nearly in real-time, researchers can assess their frequency, the materials released, and the evolution of debris disks—and potential planets—long after a star’s formation.

“This is definitely the first instance where I’ve ever observed a point of light emerge unexpectedly in an exoplanetary system,” Kalas mentioned in a statement. “It’s missing from all our prior Hubble images, indicating that we’ve just observed a violent collision between two massive entities and a vast debris cloud unlike anything in our own solar system today.”

Fomalhaut, located about 25 light-years away in the constellation Piscis Austrinus, ranks among the brightest stars visible at night. It is encircled by multiple belts of dust and debris, akin to our solar system’s Kuiper Belt beyond Neptune.

In 2004, Hubble detected a compact source within this belt, designated Fomalhaut b. Initially, scientists deliberated whether it was a planet enveloped by dust or something else. By 2008, some theorized it could represent the first exoplanet discovery accomplished with a visible light telescope.

However, over the years, the object’s behavior cast doubt. It dimmed rather than brightened, elongated outward, and ultimately disappeared. These alterations aligned with expectations for a debris cloud generated by a collision between two large bodies.

When astronomers revisited the system nearly two decades later, they did not find the original object but discovered a new source nearby within the same dust ring, indicating that another significant collision had taken place. The findings were published in the journal Science.

“What we’ve learned,” Kalas stated, “is that a large dust cloud can disguise itself as a planet for many years.”

The closeness of the two debris clouds is perplexing. If these collisions were random, they would manifest in different locations. Researchers are also unable to explain why these two impacts occurred in a brief time frame. Previous hypotheses suggested such collisions should happen every 100,000 years.

“If you had a presentation of the last 3,000 years, sped up so every year was just a fraction of a second, envision how many flashes you would observe during that period,” Kalas elaborated. “Fomalhaut’s planetary system would be shimmering with these collisions.”

The dust clouds illuminate by reflecting starlight, making them detectable by telescopes like Hubble. However, the same starlight also exerts force on the tiny dust grains, leading the clouds to disperse and fade. This phenomenon clarifies why the first cloud vanished and why the second may also diminish.

Based on the brightness of the debris, researchers approximate that the colliding objects were likely 37 miles wide—larger than most asteroids involved in known solar system impacts. Such collisions release tremendous amounts of dust, briefly illuminating otherwise unseen events.

For astronomers, this revelation presents a rare opportunity to witness the catastrophic events that once shaped—and may still shape—planetary systems throughout the galaxy, explained coauthor Mark Wyatt from the University of Cambridge. The team anticipates insights from the James Webb Space Telescope, which observes in infrared light, regarding the dust’s size and composition.

“The system serves as a natural laboratory to explore how planetesimals react during collisions,” Wyatt noted, “which in turn informs us about their composition and formation.”