Cosmic cannibalism: White dwarf star devours a Pluto-like planet

Not every meal in space is a quiet one. Sometimes stars feast on their neighbors in dramatic fashion. Recently, astronomers caught a glimpse of a white dwarf star devouring the remnants of a Pluto-like planet.

The discovery was possible thanks to the sharp ultraviolet vision of NASA’s powerful Hubble Space Telescope, revealing details invisible in ordinary light.

What is a white dwarf?

A white dwarf is the burned-out core of a once Sun-like star. Though only Earth-sized, it packs half the Sun’s mass into that tiny space. Its gravity is intense enough to rip apart icy bodies drifting too close.

In this case, scientists believe a large icy object from the star’s Kuiper Belt analog fell victim, leaving behind debris rich in water and nitrogen. These remains now spiral inward, creating a cosmic crime scene.

Such events provide scientists with rare opportunities to study planetary fragments, offering glimpses into both stellar evolution and the ultimate fate of planetary systems like our own.

When a white dwarf devours a planet

Astronomers studied the star’s light to determine the fragments’ chemical makeup. They detected carbon, sulphur, nitrogen, and oxygen. The high oxygen levels hinted at water-rich material.

“We were surprised,” said Snehalata Sahu of the University of Warwick. “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.”

Recycling material into cosmic dust

Using Hubble’s Cosmic Origins Spectrograph, the team found the fragments contained 64 percent water ice. That much ice suggested the object was not a small comet but a chunk of a dwarf planet. Hubble also revealed record levels of nitrogen in the debris.

“We know that Pluto’s surface is covered with nitrogen ices,” said Sahu. “We think that the white dwarf accreted fragments of the crust and mantle of a dwarf planet.”

Volatile-rich debris like this is invisible in regular light. Only Hubble’s ultraviolet sensitivity can reveal it. The star lies just 260 light-years away, making it a near neighbor by cosmic standards.

Once, it was a Sun-like star with planets and its own icy belt, now reduced to a dense remnant.

This transformation reminds astronomers how even stable systems eventually collapse, recycling material into cosmic dust. By tracing such changes, scientists can connect stellar death with planetary evolution.

Planetary fragments and extreme forces

The scene may mirror what awaits our Sun. Billions of years from now, it too will collapse into a white dwarf. Its gravity will pull in Kuiper Belt objects, shredding them completely apart.

“These planetesimals will then be disrupted and accreted,” said Sahu. “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.”

The team hopes to use NASA’s James Webb Space Telescope to continue exploring this intriguing system. Unlike Hubble, Webb operates in infrared, allowing it to detect faint signatures of water vapor, carbonates, and other volatile molecules hidden within the debris.

These molecules are essential for understanding how planetary fragments evolve under extreme gravitational forces.

The research will not only provide insight into the ultimate fate of icy worlds but may also shed light on the processes that deliver water and life-supporting elements to rocky planets like Earth.

In doing so, Webb may help answer fundamental questions about planetary habitability across the cosmos.

Broader implications of the research

Sahu is also interested in the interstellar comet 3I/ATLAS. She hopes to learn how much water it carries.

“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,” said Sahu.

Boris Gänsicke of the University of Warwick, who led the program, emphasized the significance of the breakthrough.

“We observed over 500 white dwarfs with Hubble. We’ve already learned so much about the building blocks and fragments of planets, but I’ve been absolutely thrilled that we now identified a system that resembles the objects in the frigid outer edges of our solar system,” said Gänsicke.

“Measuring the composition of an exo-Pluto is an important contribution toward our understanding of the formation and evolution of these bodies.”

The research is published in the journal Monthly Notices of the Royal Astronomical Society.

Image Credit: NASA, Tim Pyle (NASA/JPL-Caltech

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