astronomers have discovered huge dust clouds from violent collisions around a nearby star.
Young star systems are a place of violent collisions between rocks,comets,asteroids,and larger objects as the dust and ice of a stellar nebula coalesce into planets and moons. But the largest collisions are expected to be rare over the hundreds of millions of years it takes to form a planetary system-perhaps once every 100,000 years.
Now, astronomers have seen the aftermath of two powerful collisions within a 20-year period around a nearby star called Fomalhaut.
These are either lucky observations or a sign that collisions are more frequent than predicted during planet formation.
The events-the first was detected in 2004 and a second imaged in 2023-are the first collisions between large objects directly imaged in any solar system outside our own.
the 2023 Fomalhaut observations are discussed in a paper published in the journal Science.”We have witnessed what we believe to be a collisional event between two comet-like bodies in the Fomalhaut system,” says coauthor Maxwell Millar-Blanchaer, an assistant professor in UC Santa Barbara’s physics department.
“This is a fundamental evolutionary process in young planetary systems that’s difficult to see in real time.”
the dust cloud spewed from that violent event reflects light from the host star.
“We don’t see the two objects that crashed into each other, but we see the aftermath of this enormous impact,” says Paul Kalas, adjunct professor of astronomy at UC Berkeley. Over the course of tens of thousands of years, he says, the dust around Fomalhaut would be “sparkling with these collisions”-like fireworks.Kalas first started searching for a dusty disk around Fomalhaut in 1993, hoping to see the debris left over after planet formation. Onyl 25 light years from Earth, the star is young-about 440 million years old-and a proxy for what our solar system looked like in its formative years. Thanks to NASA’s Hubble Space Telescope (HST), he eventually found such a disk around the star and, in 2008, reported finding a bright spot near the disk that was likely a planet, the first to be imaged directly at optical wavelengths. He called it Fomalhaut b, per the naming convention for exoplanets.
That planet revelation has now turned to dust.
“This is a new phenomenon, a point source that appears in a planetary system and than over 10 years or more slowly disappears,” he says of the dust cloud. “It’s masquerading as a planet because planets also look like tiny dots orbiting nearby stars.”
Based on the brightness of both the 2004 and 2023 events, the colliding objects are at least 30 kilometers (18 miles) across-at least twice the size of## Astronomers Witness Recent Collisions Around Star Fomalhaut, Revealing Expanding Dust Clouds
Astronomers have observed two massive dust clouds surrounding the nearby star Fomalhaut, evidence of recent violent collisions within a planetary system. These events, designated cs1 (discovered previously) and cs2 (a new discovery), offer a unique glimpse into the dynamic processes shaping planetary systems and highlight potential challenges for future exoplanet detection. The findings underscore the prevalence of collisions in young planetary systems and caution against mistaking dust clouds for planets when using powerful new telescopes.
### Discovery of cs2: A Second Collision Event
Researchers, led by Dr. Pascal Kalas of UC Santa Barbara, detected the second dust cloud, cs2, using the James Webb space Telescope (HST) and the Hubble Space Telescope. The discovery was unexpected, as the team was initially focused on studying the aftermath of a collision that created the previously known dust cloud, cs1, observed decades ago.UC Santa Barbara News reports that cs2 is already 30% brighter than cs1, indicating a more recent and potentially larger impact.
### Fomalhaut: A Young and Active System
Fomalhaut is a relatively young star, approximately 44 light-years from Earth in the constellation Piscis Austrinus. its system is known to host at least three confirmed planets: Fomalhaut b, Fomalhaut c, and Fomalhaut d.NASA Exoplanet Catalog. The presence of these planets,combined with the observed dust clouds,suggests a dynamically active system where collisions are common.
The initial dust cloud, cs1, was thought to be created by a collision between two planetesimals – smaller bodies that eventually form planets. The new observations of cs2 support this idea and suggest that Fomalhaut is experiencing a period of frequent impacts. The dust is being pushed outwards by the radiation pressure of starlight.
### Comparing to the DART Mission
Kalas draws a parallel between the Fomalhaut collisions and the 2022 NASA DART (Double Asteroid Redirection Test) mission, which intentionally crashed into the asteroid moonlet Dimorphos. NASA’s DART mission page. While the cloud around Fomalhaut is estimated to be a billion times larger than the one created by DART, the underlying physics of the collision and resulting dust dispersal are similar. This comparison helps scientists understand the scale and dynamics of the events around Fomalhaut.
### Future Observations and Implications for Exoplanet Hunting
Over the next three years, Kalas and his team have been awarded telescope time with the James Webb Space Telescope’s Near-Infrared Camera (NIRCam) and the hubble Space Telescope to continue monitoring Fomalhaut. They aim to track the expansion of the dust clouds and determine their orbits, providing further insights into the collision events. UC Santa Barbara News.
The discovery has significant implications for the search for exoplanets. As future telescopes, such as the planned Habitable Worlds Observatory, become capable of directly imaging exoplanets, astronomers must be cautious about interpreting faint points of light around stars. These points of light could be planets, but they could also be dust clouds created by collisions, as seen in the Fomalhaut system. NASA’s Habitable Worlds Observatory page.”these collisions that produce dust clouds happen in every planetary system,” Kalas explains. “Once we start probing stars with sensitive future telescopes… we have to be cautious because these faint points of light orbiting a star may not be planets.”
### Research Team and Funding
The research involved contributions from scientists at UC Berkeley, Northwestern University, UCLA, the European southern Observatory in Chile, the Max planck Institute for Astronomy in Germany, the University of Cambridge, and the University of warwick in the UK. The work was supported by NASA.
This discovery highlights the chaotic and dynamic nature of young planetary systems and provides valuable data for understanding planet formation and the potential for life beyond Earth. Continued observations of Fomalhaut and other similar systems will be crucial for refining our understanding of these processes and accurately identifying true exoplanets in the future.
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