Now, scientists have spotted strong evidence that an icy, Pluto-sized world survived its star’s violent death throes and was worked to rubble in the end. A team observed volatile-rich shards of debris spiraling into a white dwarf some 260 light-years away, thanks to NASA’s Hubble Space Telescope, the first firm evidence for a Kuiper Belt–style object making it all the way through to the final stage.
The leftover star, WD 1647+375, holds the chemical fingerprints of pieces of debris — rich in carbon-, nitrogen-, sulfur-, and water ice — mixing into its otherwise simple atmosphere. White dwarfs are largely made of hydrogen and helium, and the fact that there are heavier elements present is an indication of new planetary material raining down onto the stellar corpse.
Ultraviolet fingerprints reveal volatile-rich white dwarf debris
Hubble’s ultraviolet spectroscopy identified a blend of volatiles reminiscent of the surface ices found on Pluto and other dwarf planets in our Kuiper Belt. The findings are published in Monthly Notices of the Royal Astronomical Society by a team led by the University of Warwick, who determined that the debris has been consumed from an ancient icy planetary system, knocked off trajectory and into our own Solar System.
White dwarfs’ atmospheres are like forensic slides: Metals and ices sink out of sight on short timescales, so their presence in a given layer implies ongoing delivery. Here, the team calculates that water ice could make up as much as two-thirds of the infalling material by mass — a high fraction for “polluted” white dwarfs, which most frequently display rocky, Earth-like compositions. It’s this signature of volatiles that identifies the debris as exo-Pluto–like rather than a pulverized asteroid.
A Kuiper Belt cousin that long outlived its Sun
Stars like the Sun blow off half their mass as they expand to become red giants and contract to dense white dwarfs. That dramatic mass loss loosens the gravitational grip on neighboring worlds, causing once-tranquil orbits to rock. Surviving giant planets can subsequently gravitationally scatter more distant ice-rich bodies onto long orbits that permeate the tidal boundary of the white dwarf, where they are tidally disrupted and accreted by the star.
The simplest story for WD 1647+375 involves a distant, ice-cold object hanging out in a Kuiper Belt–like reservoir for billions of years, perilously far away from the dying star during its red-giant phase.
Not until the star transitioned to a white dwarf did orbital pushing around — by resonances and secular perturbations — cause the dwarf planet to instead spiral in. The result: a short-lived, cataclysmic shredding event that spewed a plume of gas-rich debris now visible in ultraviolet light.
A preview of our Solar System’s very distant future
The finding gives a specific blueprint for how our system could one day meet its end. As the Sun ages, Mercury and Venus will be obliterated and Earth’s future is unclear, but the Jovian giants and the Kuiper Belt should endure. Once the Sun dies, ‘gravitational nudges’ from the surviving planets are expected to bump frozen bodies toward the relic star, producing characteristic volatile signatures similar to Hubble’s detection of WD 1647+375.
That would fit a general pattern. Surveys indicate that of the order of 25–50 percent of all white dwarfs have accreted planetary material polluting their atmospheres. Most appear rocky; WD 1647+375 is notable for its Pluto-like cocktail, the inference being that, when it comes to whole-system architectures — including cold, distant belts — material can endure and keep raining down on a planet long after the host star’s main-sequence life has ended.
Water delivery and planetary building blocks
The volatile load matters. If 60-plus percent of the accreted mass is water ice, that adds weight to the potential for dwarf planets and comets being good couriers of life-friendly chemicals. On Earth, the equilibrium of evidence for our oceans is a combination of endogenous outgassing and impacts by water-rich bodies migrating in from the outer Solar System. The discovery of similar cargoes in another star system implies that hydrating encounters might be a regular early chapter in planetary histories.
The nitrogen/carbon mixture found at WD 1647+375 also mirrors the chemistry observed on Pluto’s surface as well as in Kuiper Belt comets explored by spacecraft such as NASA’s New Horizons and ESA’s Rosetta, adding support to the idea that the parent body was an icy dwarf planet, not a dry, inner-system object.
Caveats and what’s next for white dwarf debris studies
Did the fragments potentially belong to an interstellar interloper? Composition alone can’t entirely rule that out, the team says, but interstellar visitors identified so far — such as 1I/’Oumuamua and 2I/Borisov — are incredibly uncommon and would need to be actively redirected into a destructive orbit. A natural connection to a long-lived reservoir in the outer disk continues to be the most straightforward interpretation.
Additional ultraviolet spectra of white dwarfs will help to explore how typical the accretion of volatile-rich material really is. Hubble is also uniquely suited for these measurements, while complementary infrared observations with the James Webb Space Telescope can explore dusty disks made by tidal disruption. Together, these data sets are transforming stellar remnants into laboratories for planetary archaeology — locations where the final crumbs betray what whole worlds were once constructed of.
“The message is clear and astonishing: That a Pluto-like planet can live in a frozen world for billions of years, then die an unbelievably dramatic death and emit detectable spectra from its atmosphere,” University of Warwick researchers stressed, among others.
There’s only that one end, but it speaks to how planetary systems can persist long after their sunsets.