White Dwarf Devours Pluto-Like Icy World

Astronomers using the Hubble Space Telescope have observed a white dwarf consuming an icy body similar to the dwarf planet Pluto, offering new insights into the existence of water-rich planets beyond our solar system.

The white dwarf, located about 255 light-years from Earth in the Milky Way, has a mass around 57% that of the Sun and a diameter roughly equivalent to Earth, despite being nearly 190,000 times more massive than our planet.

"This white dwarf likely accreted fragments from the crust and mantle of a Pluto-like icy world," said Snehalata Sahu, postdoctoral research fellow in astrophysics at the University of Warwick, lead author of the study published in Monthly Notices of the Royal Astronomical Society.

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Researchers found unusually high levels of nitrogen on the white dwarf’s surface, a chemical signature consistent with nitrogen-rich ices found on Pluto, but distinct from typical comets. Boris Gansicke, co-author and University of Warwick astrophysicist, explained that the icy body would have been torn apart by the white dwarf’s strong gravity, with fragments falling onto the star.

The rate of material accreting onto the white dwarf is equivalent to the mass of an adult blue whale hitting the star every second, sustained over at least 13 years. Hubble's Cosmic Origins Spectrograph, which observes ultraviolet light, enabled scientists to detect these chemical fingerprints.

White dwarfs are remnants of stars that exhausted their hydrogen fuel and collapsed, shedding their outer layers. Stars up to eight times the Sun’s mass end their lives as white dwarfs, and our Sun is expected to follow this path billions of years from now. The white dwarf in this study originated from a star about 50% more massive than the Sun.

Previously, astronomers observed white dwarfs accreting rocky bodies like planets, moons, and asteroids. This new detection provides evidence that icy worlds, similar to those in our solar system’s outer regions, also exist around other stars. These icy bodies are believed to play a crucial role in delivering water and organic compounds, potentially contributing to habitable environments.                                                                                           

Sahu noted, "Detecting water-rich bodies around other stars provides observational confirmation that such reservoirs exist beyond our solar system, potentially supporting the formation of habitable planets."

This discovery strengthens the understanding of how planetary systems evolve and how essential ingredients for life, such as water, may be distributed across the galaxy.