NASA/FUSE/Lynette Cook
An illustration shows colliding asteroids around the central star in the Beta Pictoris system and the formation of terrestrial planets. The insets show what two of the system’s planets might look like.
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A collision between giant asteroids has likely occurred in recent years in a neighboring galaxy called Beta Pictoris, and two different space observatories are helping to tell this story.
Located just 63 light-years from Earth, the Beta Pictoris system has long intrigued astronomers due to its proximity and age.
Although our solar system is estimated to be about 4.5 billion years old, Beta Pictoris is considered a “teenage planet system” at 20 million years old, says astronomer Christine Chen, a research scientist at Johns Hopkins University in Baltimore who has studied the system several times. has observed. time.
“That means it’s still forming,” she said during a presentation at the 244th meeting of the American Astronomical Society in Madison, Wisconsin, on June 10. “It’s a partially formed planetary system, but it’s not ready yet.”
Chen observed Beta Pictoris, which has two known gas giant planets called Beta Pictoris b and c, using the now retired Spitzer Space Telescope in 2004 and 2005. At the time, Chen and her colleagues saw several dust populations in the system.
“So I was super excited to be able to observe this system again in 2023 using the James Webb Space Telescope,” Chen said. “And I really hoped that I could understand the planetary system in much more detail, and we certainly do that.”
Since Webb opened his infrared eye on the universe in 2022, scientists have used the space observatory to peer through gas and dust to study supernovae, exoplanets and distant galaxies.
By comparing Spitzer and Webb’s observations, Chen and her colleagues realized that the data they had recorded twenty years earlier occurred at a rather coincidental time – and that two of the largest dust clouds had since disappeared.
Chen is the lead author of a study comparing the observations that was presented at the conference on Monday.
“Most of JWST’s discoveries come from things the telescope detected directly,” co-author Cicero Lu, a former Johns Hopkins doctoral student in astrophysics, said in a statement. “In this case, the story is a little different, because our results come from what JWST didn’t see.”
The team believes that the Spitzer data indicates that a pair of giant asteroids coincidentally collided just before the telescope observed the system.
“Beta Pictoris is at an age where planet formation in the terrestrial planetary zone is still ongoing through collisions with giant asteroids, so what we could be seeing here is essentially how rocky planets and other bodies form in real time,” Chen said.
When Chen and her team observed Beta Pictoris between 2004 and 2005, they likely saw glimpses of evidence of a “colliding active planetary system,” but they didn’t realize it yet, she said.
In addition to the two known planets, previous research has found evidence of comets and asteroids roaming the young system.
When the comets and asteroids collide, they create dusty debris and help form rocky planets.
The collision that occurred just before the Spitzer observations likely pulverized a huge asteroid into fine dust particles smaller than pollen or powdered sugar, Chen said.
She said the amount of dust created was about 100,000 times larger than the asteroid that killed the dinosaurs, which was estimated to be between 10 and 15 kilometers wide. The dust was then pushed out of the planetary system by radiation from the central star, which is slightly hotter than our Sun.
Initially, astronomers thought that small bodies collided with each other and replenished the dust clouds seen in Beta Pictoris over time. But the powerful Webb telescope could not detect dust.
Although giant gas planets have formed in the system, rocky planets are likely still forming.
Astronomers expect to make more observations of the system to see if more planets will appear. In the meantime, studying the system can help astronomers better understand what the early days of our own solar system were like.
“The question we are trying to contextualize is whether this entire 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, a doctoral student in astrophysics at Johns Hopkins, in a statement. “We’re actually trying to understand how weird or average we are.”
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