DESI side project reveals the spectra of disintegrated exoplanets

August 2, 2026 feature DESI side project reveals the spectra of disintegrated exoplanets Sam Jarman Author Gaby Clark Scientific Editor Robert Egan Senior Editor Using spectral data from the Dark Energy Spectroscopic Instrument (DESI), astronomers have gained some of the clearest evidence yet that white dwarf stars are accreting debris from disintegrating exoplanets. Captured while DESI was unable to study its primary targets: distant galaxies, the results provide unprecedented insights into the chemical makeup of rocky exoplanets, revealing compositions remarkably similar to the planets and asteroids of our own inner solar system. The results have been published in Monthly Notices of the Royal Astronomical Society. Falling planetary fragments When stars like our sun reach the end of their lives, they leave behind a hot, dense core made almost entirely of hydrogen and helium—a white dwarf. But this often isn't the end of the story for the star's composition: rocky bodies that once orbited safely farther out can be gravitationally scattered inward, where tidal forces gradually tear them apart. Eventually, this debris falls onto the white dwarf's surface, polluting its atmosphere with elements heavier than helium (all termed 'metals' in astrophysics). To date, between 20% and 50% of the hundreds of thousands of white dwarfs observed by astronomers carry signatures of metals in their stellar spectra, offering a unique glimpse of the compositions of the exoplanets that once orbited them. Of these, just over 1,750 are known to be actively accreting planetary debris—and of those, only a few dozen have spectra altered enough to yield reliable data on their metal compositions, making them especially valuable targets. DESI side project Currently, the best resource available for studying these rare spectra is DESI, an instrument in the Arizona desert designed to probe the history of the universe's expansion through observations of distant galaxies. Yet during its primary five-year survey, conditions weren't always favorable for observing its main target. Rather than wasting valuable observation time, the collaboration used these gaps to study targets closer to home. "We are lucky enough to get a lot of white dwarfs observed as a side project," explains the study's lead author, Paula Izquierdo of the University of Warwick. "Among those, we found these ones which are super metal-enriched." In their latest study, the DESI collaboration examined the spectra of 12 highly metal-enriched white dwarfs in unprecedented detail. One key goal was to compare the observed spectra with the known compositions of the inner planets of our own solar system. "In order to understand if our solar system is common or special in terms of its composition, we need a sizable number of exoplanets whose chemical composition is derived," Izquierdo continues. "Currently, this can only be done by analyzing this type of white dwarf." Benchmarking our solar system Broadly, the team's results confirmed that the debris accreting onto white dwarfs has a composition familiar to planetary astronomers. "Most of the accreted bodies by white dwarfs show the major rock-forming elements that we see in our solar system, resembling the composition seen in primitive meteorites," Izquierdo says. Across the 12 systems, the astronomers identified between three and 10 different heavy elements, including oxygen, magnesium, silicon, calcium and iron—all key rock-forming elements found on planets like Earth and Mars. Six of the spectra were clean enough to support a more detailed compositional analysis: Four pointed to dry, rock-forming compositions, while distinct oxygen signatures in the other two hinted at oxide compounds, possibly originating from water-rich planetesimals akin to early Earth. Ultimately, although DESI was designed for a completely different purpose, the team's results confirm that the instrument is an excellent tracer of metal-rich white dwarfs. Further analysis of DESI's ongoing observations could offer fresh insight into the similarities and differences between planet formation across different star systems—and new clues about the thousands of rocky exoplanets astronomers have already discovered. Written for you by our author Sam Jarman, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you. Publication details Paula Izquierdo et al, First planetesimals from DESI DR1: 12 highly metal-rich white dwarfs, Monthly Notices of the Royal Astronomical Society (2026). DOI: 10.1093/mnras/stag1353. On arXiv: DOI: 10.48550/arxiv.2607.14251 Journal information: Monthly Notices of the Royal Astronomical Society , arXiv © 2026 Science X Network