- White dwarfs are the remaining hot, dense cores of dead stars. They can sometimes still have planets and other rocky debris orbiting them.
- A white dwarf 260 light-years away is consuming the leftover pieces of a former Pluto-like object. NASA’s Hubble Space Telescope made the discovery.
- Hubble analyzed a fragment rich in water ice, nitrogen and other volatiles. This shows the original object it came from was similar to Pluto in our own Kuiper Belt.
Hubble sees hungry white dwarf devour icy Pluto-like world
Astronomers have found that a relatively close white dwarf – the remaining hot, dense core of a dead star – is having a planetary snack. An international team of researchers, led by the University of Warwick in the U.K., said on September 18, 2025, that a white dwarf is consuming a fragment of a former Pluto-like object. The researchers said they found evidence of the cosmic meal when viewing the white dwarf WD 1647+375 in ultraviolet light with NASA’s Hubble Space Telescope. The white dwarf’s strong gravity pulled in the icy Pluto-like world and then tore it to pieces.
When the researchers analyzed the chemical composition of the fragment, they found, surprisingly, that it contained a lot of water ice.
The white dwarf is relatively close by, at about 260 light-years away.
The researchers published their peer-reviewed findings in the Monthly Notices of the Royal Astronomical Society on September 18, 2025.
A surprising detection of water ice
Using its Cosmic Origins Spectrograph, Hubble analyzed the chemical composition of the fragment and found some surprises. It detected volatiles – substances with low boiling points – including carbon, sulfur, nitrogen and a high oxygen content. Together, those suggest a strong presence of water ice. It also means that the fragment likely came from an icy body similar to Pluto or other similar objects in the Kuiper Belt of our own solar system. Lead author Snehalata Sahu at the University of Warwick in the U.K. explained:
We were surprised. We did not expect to find water or other icy content. This is because the comets and Kuiper Belt-like objects are thrown out of their planetary systems early, as their stars evolve into white dwarfs. But here, we are detecting this very volatile-rich material. This is surprising for astronomers studying white dwarfs as well as exoplanets, planets outside our solar system.
Overall, water ice composes about 64% of the rocky fragment. That means the original object the fragment came from was likely fairly massive, similar to Pluto. It also means the object was far away from its white dwarf star, in a region similar to our Kuiper Belt.
In addition, Hubble detected a large amount of nitrogen, about 5% of the fragment’s mass. This is also similar to Pluto, which has nitrogen ices on its surface. In fact, this is the largest amount of nitrogen ever found in debris around a white dwarf. Sahu said:
We know that Pluto’s surface is covered with nitrogen ices. We think that the white dwarf accreted fragments of the crust and mantle of a dwarf planet.
White dwarf eating a Pluto-like object. Video via NASA Goddard.
Cosmic crime scene
The researchers liken the destruction of the former icy object to a cosmic crime scene. Sahu said:
It is not unusual for white dwarfs to show signatures of calcium, iron and other metal from the material they are accreting (absorbing). This material comes from planets and asteroids that come too close to the star and are shredded and accreted. Analyzing the chemical make-up of this material gives us a window into how planetesimals outside the solar system are composed.
In this way, white dwarfs act like cosmic crime scenes; when a planetesimal falls in, its elements leave chemical fingerprints in the star’s atmosphere, letting us reconstruct the identity of the ‘victim.’ Typically, we see evidence of rocky material being accreted, such as calcium and other metals, but finding volatile-rich debris has been confirmed in only a handful of cases.
James Webb Space Telescope and 3I/ATLAS
Now, the researchers are hoping that NASA’s James Webb Space Telescope will also be able to take a look at WD 1647+375. It could further observe volatiles such as water vapor and carbonates, in infrared light.
In addition, Sahu also noted that the observations of the interstellar comet 3I/ATLAS can provide more clues about planetary formation:
These types of studies will help us learn more about planet formation. They can also help us understand how water is delivered to rocky planets.
A glimpse of our solar system’s future
Seeing the fate of this former Pluto-like world gives astronomers a glimpse of what will eventually happen in our own solar system. Indeed, billions of years from now, the sun will also die, first swelling into a red giant star and then collapsing into a white dwarf. The immense gravity of the white dwarf will pull in objects like Pluto and others in the Kuiper Belt. Then they too will be consumed. Sahu said:
If an alien observer looks into our solar system in the far future, they might see the same kind of remains we see today around this white dwarf.
But some planets could survive, however, and continue to orbit the white dwarf, such as this Earth-sized exoplanet.
Intriguingly, in 2021, astronomers reported finding evidence of vaporized planetary crusts in white dwarfs. Those former planets, however, were more like Earth or Mars in their composition.
Bottom line: NASA’s Hubble Space Telescope has caught a hungry white dwarf devouring the leftover pieces of a former icy, Pluto-like world 260 light-years away.
Source: Discovery of an icy and nitrogen-rich extrasolar planetesimal
Via NASA
Via University of Warwick
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