Astronomers witness a spectacular display of fireworks in the form of violent collisions around a nearby star, Fomalhaut. These collisions, occurring within a 20-year period, are either a stroke of luck or an indication that collisions during planet formation are more frequent than previously thought. The events, witnessed in 2004 and 2023, mark the first direct imaging of large object collisions in any solar system outside our own.
The aftermath of these collisions is a mesmerizing sight. Paul Kalas, an astronomer at the University of California, Berkeley, describes the dust around Fomalhaut as 'sparkling with these collisions' over tens of thousands of years, resembling twinkling holiday lights. The Hubble Space Telescope's image reveals a debris ring and dust clouds, with the 2023 observation providing crucial insights.
Kalas's journey began in 1993 when he sought to uncover the dusty disk around Fomalhaut, a young star resembling our solar system's early years. In 2008, he discovered a bright spot near the disk, initially believed to be a planet, named Fomalhaut b. However, further observations revealed that this 'planet' was likely a dust cloud resulting from the collision of planetesimals.
The colliding objects, at least 60 kilometers in diameter, are referred to as planetesimals, similar in size to asteroids and comets in our solar system. Kalas emphasizes that Fomalhaut's youth provides a unique glimpse into the violent period of our solar system's formation, where small worlds were frequently cratered and destroyed.
The 2023 observations, detailed in a Science journal paper, offer a rare opportunity to study planetesimal behavior during collisions. Mark Wyatt, a colleague of Kalas, highlights the significance of these findings in estimating the size of colliding bodies and their abundance in the disk.
Fomalhaut, a 16-times more luminous star than our Sun, hosts a large belt of dusty debris at a distance of 133 astronomical units. Kalas's initial assumption of a planet was later corrected to a dust cloud, prompting caution for astronomers when interpreting future exoplanet images.
