Could that spark of light near the distant star be the birth of a new planet or perhaps the shiny trail left behind by a galactic collision? The astronomers gazing at the neighboring star Fomalhault have found the hard way that looks can definitely be deceiving. In an historic feat, the astronomers have managed to capture the image of the effects of two colossal collisions of large planetesimals that occurred in 2004 and 2023 in the planetary system just 25 light-years from the earth. This is the first recorded instance of its kind, the first collision ever witnessed outside the solar perimeter.
Luminous and 440 million years young, A-type star Fomalhault, located in the constellation Piscis Austrinus, presents a young staric system where icy and volatile-enriched planetesimal objects, tens of kilometers in size, collide and impact each other in the kaleidoscopic process of planetary formation. Such megacolisions are very rare and happen only once every 100,000 years, but this time, two events have been recorded in just two decades. “We just witnessed the collision of two planetesimals and the dust cloud that gets spewed out of that violent event, which begins reflecting light from the host star,” stated Paul Kalas, a member of the University of California, Berkeley. The scientists did not record the actual collision but rather the expanding clouds that followed.
The first cloud, provisionally labeled Fomalhaut b, was picked up in 2008 with the Hubble Space Telescope and estimated to be the first actual planetary body ever directly imaged in visible light orbiting another star. However, its orbit and the gradual reduction in its brightness suggested that its appearance actually hid a cloud of material disguising itself as a planet. The final cloud, Fomalhaut cs2, made its appearance in the year 2023, and now its luminosity is already 30 percent more than the original cloud, which was discovered in 2008. This cloud is still observable, confirming data collected in August 2025.
The dynamics that take place during these collisions are the key to understanding planetary system formation. When the planetesimals collide at a very high speed and have a diameter of 60 kilometers (37 miles), the kinetic energy breaks up the planetesimal material and ice into very fine dust. The force of radiation from the star causes the smallest particles to drift out into the surrounding disk. This mechanism is the same in principle that took place during the creation of the dust cloud that NASA’s DART mission accomplished on the Dimorphos moon in 2022 when their spacecraft collided on the surface. The size is the only difference: the Fomalhaut cloud is a billion times larger.
Another perspective emerges with chemical signatures. Past discoveries of carbon monoxide gas within the planetary system of Fomalhaut confirm that its planetesimals contain high levels of volatiles like hydrogen, nitrogen, oxygen, and methane compounds that have low vaporization temperatures. This matches perfectly with the icy comets within our own solar system, which share analogous models for development and migrations. These volatiles within planetesimals directly influence the delivery mechanisms for life-giving water and organic compounds during planetary collisions that are both destructive and life-giving at the same time.
However, the context in which these occurrences took place is also very fascinating. S1 and M were detected at what appears to be the inner region of the outer disk for Fomalhaut, where the disk is 133 astronomical units away from the star, well over three times the orbit out to the Kuiper Belt. While the sharp truncation of the disk indicates possible shepherding by unseen masses, the sudden emergence of both S1 and M in the potentially collision-rich region close to the inner part of the disk makes one wonder whether local dynamic factors specifically, disk disk/planet resonances are not driving the significantly enhanced rates of collisions relative to theoretical predictions.
Top-of-the-line telescopes are essential in unlocking these secrets. Hubble’s optical imaging was the first to detect this phenomenon, but once the James Webb Space Telescope’s Near-Infrared Camera begins analyzing cs2, it should offer a whole new set of information. The Webb telescope’s infrared capabilities are sensitive enough not only to measure the size of the dust particles but also detect water ice. Its brightness, size, and orbital alterations over the course of the next three years may help scientists understand whether it potentially becomes brightest, stretches into a cometary shape, or crashes into other debris.
These results also contain a warning for exoplanet seekers. As Kalas has warned,“Once we start probing stars with sensitive future telescopes such as the Habitable Worlds Observatory, which aims to directly image an Earth-like exoplanet, we have to be cautious because these faint points of light orbiting a star may not be planets.” Clouds of dust like cs1 and cs2 can fool observers by producing spurious signals of planets for many years. For observers, learning whether there was a real planet there or just the sparkle of a cosmic collision is going to involve more than just greater resolution: it is also going to involve learning more about the hellish, volatile worlds that planets hail from.
