Webb telescope finds evidence of Mars-sized planetary embryos colliding
- Astronomers using NASA’s James Webb Space Telescope have identified rare extreme debris disks around young star systems, capturing evidence of colossal collisions between Mars-sized planetary embryos.
- Young stars begin with a gas-rich protoplanetary disk where forming planets reside, but that environment eventually transitions into a gas-poor debris disk.
- Kate Su of the Space Science Institute in Boulder, Colorado, led a team of astronomers that assembled a sample of 21 extreme debris disks to study with Webb...
Astronomers using NASA’s James Webb Space Telescope have identified rare extreme debris disks around young star systems, capturing evidence of colossal collisions between Mars-sized planetary embryos. The findings, published Oct. 1 in The Astrophysical Journal, offer new insight into the violent processes that shaped the early solar system, including the impact that formed Earth’s Moon.
Webb Targets Rare Extreme Debris Disks
Young stars begin with a gas-rich protoplanetary disk where forming planets reside, but that environment eventually transitions into a gas-poor debris disk. While the retired Spitzer Space Telescope previously identified an unusual subclass known as extreme debris disks containing exceptionally large amounts of warm dust close to their stars, researchers had limited information about them. Theoretical models suggest these systems should be common, but observations indicate that only about 1% of young stars display observable signs of this stage.
Kate Su of the Space Science Institute in Boulder, Colorado, led a team of astronomers that assembled a sample of 21 extreme debris disks to study with Webb and archival Spitzer data. Of that sample, 16 disks were studied with Webb, including 12 newly observed systems and four follow-up observations. This is the first time we have gathered enough systems to truly understand this subclass that we call extreme debris disks,
Su said.
Planetary Embryos Smash Together
Mid-infrared spectra gathered by Webb and Spitzer revealed that extreme debris disks feature small dust grains, high concentrations of warm dust, and irregular brightness fluctuations over time. By examining the minerals present, the researchers divided the systems into silica-rich disks, which contain volcanic glass like obsidian, and silica-poor disks, which contain minerals such as forsterite. Roughly one-third of the disks in the sample are silica-rich and likely formed from energetic collisions between Mars-sized bodies that vaporized substantial rocky material. The remaining two-thirds are silica-poor and appear to result from lower-energy impacts between Moon-sized objects.
Coauthor Agnes Kospal of the Konkoly Observatory in Budapest, Hungary, noted the significance of the observations. To just see their mid-infrared emission and beautiful spectral features with Webb, which allowed us to identify their compositions, was the most exciting thing for me,
Kospal said. We have no other way to study these planetary embryos directly because they are too small.
Reconstructing Solar System History
The study found a clear age difference between the two groups, with silica-rich disks appearing exclusively around stars younger than 300 million years. This timeline matches computer simulations showing terrestrial planets emerging within the first few hundred million years, aligning with estimates that Earth and the Moon formed roughly 100 million years after the Sun. Meanwhile, silica-poor disks occur around stars of varying ages and show stronger brightness changes driven by rapid debris evolution and orbital changes.
Attila Moor of the Konkoly Observatory pointed out that further observations are required to test current hypotheses about the aging of these systems. Of course, there’s many things we still don’t know about these disks,
Moor said. We expect no silica-rich systems among older extreme debris disks. We only have three disks in our sample that fit that age criteria, so it’ll be nice to observe more of these systems to confirm our hypothesis.