Two different space telescopes took images 20 years apart of the same region around a star called Beta Pictoris. Scientists believe that the massive amount of dust seen in the 2004-2005 Spitzer Space Telescope image suggests an asteroid collision that had largely cleared by the time the James Webb Space Telescope took its images in 2023. Credit : Roberto Molar Candanosa/Johns Hopkins University, with Beta Pictoris concept by Lynette Cook/NASA.
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Two different space telescopes took images 20 years apart of the same region around a star called Beta Pictoris. Scientists believe that the massive amount of dust seen in the 2004-2005 Spitzer Space Telescope image suggests an asteroid collision that had largely cleared by the time the James Webb Space Telescope took its images in 2023. Credit : Roberto Molar Candanosa/Johns Hopkins University, with Beta Pictoris concept 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 early age and frenzied planet-forming activity.
The observations highlight the erratic processes that shape star systems like our own, and offer a unique insight into the early stages of planet formation.
“Beta Pictoris is at an age where planet formation in the terrestrial planet zone is still taking place through giant asteroid collisions, so what we were able to see here is basically how rocky planets and other bodies are forming in real time,” said Christine Chen, a Johns Hopkins University astronomer who led the research.
The findings will be presented today at the 244th meeting of the American Astronomical Society in Madison, Wisconsin.
Chen’s team spotted 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. Using Webb’s detailed measurements, the team tracked the dust particles. composition and size in the exact region previously analyzed by Spitzer.
The researchers focused on the heat emitted by crystalline silicates — minerals commonly found around young stars as well as on Earth and other celestial bodies — and found no trace of the particles previously observed in 2004-05. This suggests a cataclysmic collision between asteroids and other objects about 20 years ago that crushed the bodies into fine dust particles smaller than pollen or powdered sugar, Chen said.
“We think all that dust is what we originally saw 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, our best explanation is that we were actually witnessing the aftermath of a rare, cataclysmic event between large asteroid-sized bodies, marking a complete change in our understanding of this star system.”
The new data suggest that dust that was scattered outward by radiation from the system’s central star is no longer detectable, Chen said. Initially, dust near the star heated up and emitted thermal radiation that Spitzer’s instruments identified. Now the dust, which has cooled as it moves away from the star, no longer emits these heat elements.
When Spitzer was collecting earlier data, scientists assumed that something like small bodies that were grinding together would mix over time and periodically add dust. But Webb’s new observations show that the dust disappeared and was not replaced. The amount of dust ejected is about 100,000 times the size of the asteroid that killed the dinosaurs, Chen said.
Located about 63 light-years from Earth, Beta Pictoris has long been the focus of astronomers’ attention because of its proximity and the random processes where collisions, space weathering and other planet-forming factors will determine the fate of the system.
At just 20 million years old—compared to our 4.5 billion-year-old solar system—Beta Pictoris is at a key age for giant planets to form, but terrestrial planets may still be developing. It has at least two known gas giants, Beta Pic bac, which also influence 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 an even more fundamental question: Are planetary systems like the Solar System that rare?” said co-author Kadin Worthen, a doctoral student in astrophysics at Johns Hopkins. “Basically, we’re trying to understand how weird or average we are.”
The new findings also underscore the Webb Telescope’s unparalleled ability to reveal the complexities of exoplanets and star systems, the team says. 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 perturbations affect planets’ atmospheres, water content and other key aspects of habitability.
“Most of JWST’s discoveries come from things that the telescope directly detected,” said co-author Cicero Lu, a former Johns Hopkins astrophysics doctoral student. “In this case, the story is a bit different because our results come from what JWST didn’t see.”
Other authors include Yiwei Chai and Alexis Li of Johns Hopkins; David R. Law, BA Sargent, GC Sloan, Julien H. Girard, Dean C. Hines, Marshall Perrin, and Laurent Pueyo of the Space Telescope Science Institute; Carey 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; Isabel Rebollido of the European Space Agency; and Christopher Stark of NASA’s Goddard Space Flight Center.