Two different space telescopes took snapshots 20 years apart of the same region around the star, called Beta Pictoris. Scientists theorize that the massive amount of dust seen in the 2004-2005 image from the Spitzer Space Telescope indicates an asteroid collision that had largely disappeared by the time the James Webb Space Telescope took its images in 2023. Credit: Roberto Molar Candanosa/Johns Hopkins University, with Beta Pictoris concept art by Lynette Cook/NASA.
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Two different space telescopes took snapshots 20 years apart of the same region around the star, called Beta Pictoris. Scientists theorize that the massive amount of dust seen in the 2004-2005 image from the Spitzer Space Telescope indicates an asteroid collision that had largely disappeared by the time the James Webb Space Telescope took its images in 2023. Credit: Roberto Molar Candanosa/Johns Hopkins University, with Beta Pictoris concept art by Lynette Cook/NASA.
Astronomers have captured what appears to be a snapshot of a massive collision of giant asteroids in Beta Pictoris, a neighboring star system known for its young age and violent planet-forming activity.
The observations highlight the changing processes that shape star systems like ours, offering a unique glimpse into the primordial stages of planetary formation.
“Beta Pictoris is at an age when planet formation in the terrestrial planet zone is still going on through collisions of giant asteroids, so what we can see here is basically how rocky planets and other bodies are forming in real time,” said Christine Chen, an astronomer at Johns Hopkins University who led the study.
The insights will be presented today at the 244th meeting of the American Astronomical Society in Madison, Wisconsin.
Chen’s team noticed significant changes in the energy signatures emitted by dust grains around Beta Pictoris by comparing new data from the James Webb Space Telescope with Spitzer Space Telescope observations from 2004 and 2005. With Webb’s detailed measurements, the team traced the dust particles’ composition and size in the exact region previously analyzed by Spitzer.
Focusing on the heat emitted by crystalline silicates – minerals commonly found around young stars as well as on Earth and other celestial bodies – the scientists found no trace of the particles previously observed in 2004-05. This suggests that A cataclysm between asteroids and other objects occurred about 20 years ago, pulverizing the bodies into fine dust particles smaller than pollen or powdered sugar, Chen said.
“We think all this dust is what we saw originally in the 2004 and 2005 Spitzer data,” said Chen, who is also an astronomer at the Space Telescope Science Institute. “With Webb’s new data, the best explanation we have is that we actually witnessed the aftermath of a rare, cataclysmic event between large asteroid-sized bodies that marked a complete change in our understanding of this star system.”
The new data suggest that dust that was blown outward by radiation from the system’s central star is no longer detectable, Chen said. Initially, the dust near the star heats up and emits thermal radiation that Spitzer’s instruments detect. Now the dust, which has cooled as it moves away from the star, no longer emits these thermal characteristics.
When Spitzer collected the earlier data, scientists assumed that something like small grinding bodies would move and replenish the dust steadily over time. But Webb’s new observations show that the dust is gone and not replaced. The amount of dust kicked up is about 100,000 times the size of the asteroid that killed the dinosaurs, Chen said.
Beta Pictoris, located about 63 light-years from Earth, has long been a focal point for astronomers because of its proximity and the random processes in which collisions, space weathering and other planet-forming factors will dictate the fate of the system.
At just 20 million years old—compared to our solar system’s 4.5 billion years—Beta Pictoris is at a key age when giant planets formed, but terrestrial planets may still be developing. There are at least two known gas giants, Beta Pic b and c, that also affect the surrounding dust and debris.
“The question we’re trying to contextualize is whether this whole process of terrestrial and giant planet formation is common or rare, and the even more fundamental question: Are planetary systems like the solar system that rare?” said co-author Kadin Worthen, PhD student in astrophysics at Johns Hopkins. “We’re basically trying to figure out how weird or average we are.”
The new insights also highlight the Webb telescope’s unparalleled ability to reveal the intricacies of exoplanets and star systems, the team reports. They offer key clues about how the architectures of other solar systems resemble our own, and are likely to deepen scientists’ understanding of how early shocks affect the planets’ atmospheres, water content and other key aspects of habitability.
“Most of JWST’s discoveries come from things that the telescope has detected directly,” said co-author Cicero Lu, a former Johns Hopkins astrophysics postdoctoral fellow. “In this case, the story is a bit different because our results come from what JWST didn’t see.”
The other authors include Yiwei Chai and Alexis Li of Johns Hopkins; David R. Lowe, BA Sargent, GC Sloan, Julien H. Girard, Dean C. Hines, Marshall Perrin, and Laurent Pueyo of the Space Telescope Science Institute; Kerry M. Lisse of the Johns Hopkins University Applied Physics Laboratory; Dan M. Watson of the University of Rochester; Jens Kammerer of the European Southern Observatory; Isabelle Rebolido of the European Space Agency; and Christopher Stark of NASA’s Goddard Space Flight Center.
