Webb telescope finds extreme debris disks are rare, offering clues to how Earth's Moon formed
Researchers led by Kate Su of the Space Science Institute, using NASA's James Webb Space Telescope and archival Spitzer data, compiled 21 'extreme debris disks' around young stars. They found only about 1% of young stars show these signatures, far fewer than theoretical models predicted. The team's study, published in The Astrophysical Journal, splits the disks into silica-rich ones, likely produced by high-energy collisions between Mars-sized bodies, and silica-poor ones, linked to less energetic impacts.
Bottom line — Silica-rich disks appear only around stars younger than 300 million years, matching the timing when Earth and the Moon are thought to have formed.
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Scientists theorise that the Earth-Moon system resulted from a collision with a Mars-sized object called Theia about 4.5 billion years ago, according to Universe Today.
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Simulations cited by the team suggest terrestrial planets should form within the first few hundred million years, which the silica-rich disk ages appear to fit, according to ScienceDaily and ESA/Webb.
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Kate Su said the team had previously had limited information on these disks, describing them as 'weird and very different' from typical cold debris disks such as Vega and Fomalhaut.
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Agnes Kospal of Konkoly Observatory called seeing the disks' mid-infrared spectral features with Webb 'the most exciting thing' for her, noting planetary embryos are otherwise too small to study directly.
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Attila Moor of Konkoly Observatory said the team expects no silica-rich systems among older disks, but has only three disks in its sample meeting that age criterion, so further observations are needed to confirm the hypothesis.
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The silica-poor distribution is broadly consistent with the Late Heavy Bombardment hypothesis, in which giant planets migrated and disrupted smaller bodies' orbits, according to the ESA/Webb summary.
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Researchers expect the findings to be tested further as the sample grows, with planned follow-up from the Nancy Grace Roman Space Telescope and the PRIMA mission, according to Universe Today.