In a rare astronomical event, NASA’s Hubble Space Telescope captured the aftermath of colliding space rocks in a nearby planetary system. Initially, astronomers spotted a bright object in the sky and assumed it was a dust-covered exoplanet reflecting starlight. However, when that object vanished and a new bright object appeared, the international team—including Northwestern University’s Jason Wang—realized they were witnessing not planets, but the glowing remnants of a cosmic collision.

Two separate, violent collisions produced bright clouds of debris within the same planetary system, providing a rare real-time view of planet formation and the materials that combine to create new worlds. The findings are published in the journal Science.

Figure 1. Conceptual Image of a Cosmic Smashup Near Fomalhaut

“Seeing a new light source in the star’s dust belt was completely unexpected,” said Jason Wang. Figure 1 shows Conceptual Image of a Cosmic Smashup Near Fomalhaut.

“Our main hypothesis is that we observed two collisions between planetesimals—small rocky bodies similar to asteroids—over the past two decades. Such collisions are exceedingly rare, and this is the first observation of this kind outside our solar system.

Studying planetesimal collisions is crucial for understanding planet formation and provides insights into asteroid structures, which is valuable for planetary defense initiatives like NASA’s Double Asteroid Redirection Test (DART).”

“This is the first time I’ve ever seen a point of light suddenly appear in an exoplanetary system,” said lead author Paul Kalas, an astronomer at the University of California, Berkeley. “It was absent in all previous Hubble images, indicating a violent collision between two massive objects and a debris cloud unlike anything in our solar system today.”

Jason Wang, an expert in exoplanet imaging, is an assistant professor of physics and astronomy at Northwestern University’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).

Site of the Cosmic Smashup

For years, astronomers have debated the nature of Fomalhaut b, a bright object just outside the star Fomalhaut, located 25 light-years away in the Piscis Austrinus constellation. Fomalhaut, more massive than the Sun, is surrounded by an extensive system of dusty debris belts.

“The system has one of the largest dust belts we know of,” said Jason Wang, who has been monitoring it for two decades. “That makes it an ideal target for study.”

Since its discovery in 2008, it has been unclear whether Fomalhaut b is a planet or an expanding dust cloud. In 2023, Hubble observations revealed that the original bright source had vanished, while a new bright point appeared nearby.

“Our initial goal was to monitor Fomalhaut b, which we thought was a planet,” Wang explained. “We assumed the bright light corresponded to the known source, but careful comparison with previous images showed it was not the same. That was both exciting and puzzling.”

Double Impact

The disappearance of Fomalhaut b—now designated Fomalhaut cs1—supports the idea that it was a dissipating dust cloud, likely the result of a collision. The emergence of a second bright point, Fomalhaut cs2, reinforces the conclusion that neither object is a planet, but rather the dusty remnants of dramatic collisions between planetesimals, the rocky building blocks of planets.

The position and brightness of Fomalhaut cs2 closely resemble those of Fomalhaut cs1 when first observed two decades ago. By analyzing the system, the team estimated the frequency of such planetesimal collisions.

“Theory predicts one collision every 100,000 years or more. Yet, in just 20 years, we’ve observed two,” said Paul Kalas. “If you imagined a 3,000-year movie sped up so each year is a fraction of a second, Fomalhaut’s system would be sparkling with these collisions.”

Jason Wang helped validate this remarkable finding, contributing one of four independent analyses confirming the detection of two transient events in Fomalhaut’s dust belt. “This is the first time we’ve seen something like this,” Wang said. “We had to ensure our images were reliable and that the collision properties were measured correctly. My calculations show that all four independent analyses confidently detect a new source near the star.”

A Warning Story

While the discovery provides a rare opportunity to observe collisions in real time, it also underscores the risk of mistaking the dusty remnants of such events for actual planets reflecting starlight.

As next-generation telescopes like the Giant Magellan Telescope aim to image habitable-zone planets around nearby stars, distinguishing these transient collision clouds from true exoplanets will be essential.

“Fomalhaut cs2 looks exactly like an extrasolar planet reflecting starlight,” said Paul Kalas. “What we learned from cs1 is that a large dust cloud can masquerade as a planet for many years. This serves as a caution for future missions targeting exoplanets in reflected light.”

Although Fomalhaut cs1 has faded, the team will continue monitoring the system, tracking Fomalhaut cs2 and investigating the dynamics of these collisions [1]. Observations will be conducted with NASA’s James Webb Space Telescope (JWST) using its Near-Infrared Camera (NIRCam), which can provide color data that Hubble could not. This information will reveal the size and composition of dust grains, including whether the clouds contain water or ice.

“Due to Hubble’s age, it can no longer gather reliable data on the system,” said Jason Wang. “Fortunately, we now have JWST. Our approved program will follow up on this planetesimal collision to study the new circumstellar source and the nature of its two parent planetesimals.”

Reference:

1. https://phys.org/news/2025-12-hubble-captures-rare-collision-nearby.html

Cite this article:

Janani R (2025), Hubble Observes Rare Collision in Nearby Star System, AnaTechMaz, pp.710