NASA’s Webb maps 21 extreme debris disks from planet smashups

NASA said on October 1, 2026 that astronomers using the James Webb Space Telescope have assembled a sample of 21 extreme debris disks, young stellar systems littered with warm dust from violent collisions. The team's findings were published Thursday in The Astrophysical Journal, the agency said.

What the team studied

According to NASA, the environment around a star changes as it ages, starting with a gas-rich protoplanetary disk and evolving into a gas-poor debris disk. NASA's retired Spitzer Space Telescope examined the debris disk stage and discovered a subclass called extreme debris disks, systems with unusually large amounts of warm dust close to the star, in the region comparable to where rocky planets orbit in our solar system.

A team led by Kate Su of the Space Science Institute in Boulder, Colorado investigated these objects with Webb. NASA said the systems are rare: scientists estimate roughly only 1% of young stars show observable signatures of this phase based on the data collected so far, contrary to theoretical predictions that many should be visible.

The sample of 21 disks includes five from Spitzer's archival data and 16 from Webb, with 12 newly observed disks and follow-up observations on four of Spitzer's.

Dust chemistry points to the size of the impacts

The team confirmed that extreme debris disks share three key properties, according to NASA: smaller dust grains than those in protoplanetary or classic debris disks, a high concentration of warm dust, and irregular brightness variations, all revealed by mid-infrared spectra from Webb and Spitzer.

Studying the mineralogy, the astronomers sorted the sample into silica-rich and silica-poor disks. NASA said about one-third is silica-rich, suggesting these disks are produced by high-energy impacts between Mars-sized bodies where a significant portion of the material is vaporized. The remaining two-thirds is silica-poor, indicating collisions on smaller scales, like grazing, between Moon-sized objects.

Silica-rich disks are found only around stars younger than 300 million years, while silica-poor disks persist across a broad range of ages and often show greater brightness variability, the agency said. The team proposes that this variability is driven by the rapid evolution of fresh debris through orbital changes and additional impacts.

Links to our own solar system

NASA said the findings can be applied to our solar system, which may have experienced more than one extreme debris disk phase. Simulations suggest terrestrial planets such as Earth should form within the first few hundred million years of a solar system's formation, a period that fits the ages of the silica-rich disks observed so far and aligns with the estimate that Earth and the Moon formed around 100 million years after the Sun, with the Moon likely resulting from a collision between Earth and a Mars-sized object.

If older silica-poor disks and their random intervals of infrared brightness reflect orbital instability, NASA said, that would be broadly consistent with the Late Heavy Bombardment hypothesis, in which migrating gas giants disrupted the orbits of smaller bodies and triggered catastrophic collisions.

What the researchers say

"This is the first time we have gathered enough systems to truly understand this subclass that we call extreme debris disks," said Su, lead author of the paper, adding that before Webb the team had limited information.

Coauthor Agnes Kospal of Konkoly Observatory in Budapest, Hungary said: "We have no other way to study these planetary embryos directly because they are too small." Coauthor Attila Moor, also of Konkoly Observatory, said the team expects no silica-rich systems among older extreme debris disks but has only three disks in the sample that fit that age criteria, so more observations are needed to confirm the hypothesis.

Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

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