ASTRONOMERS FIND TWO DEBRIS RINGS AROUND WHITE DWARF

Astronomers at the University of Trieste and the University of Warwick say they have found two rings of planetary debris around WD J1328−1450, a white dwarf about 1,600 light years from Earth. The team published its findings in Nature Astronomy. Using the X-shooter instrument on the European Southern Observatory’s Very Large Telescope in Chile, the researchers detected two concentric rings of gas separated by a gap. They say previously identified gas discs around white dwarfs have formed a single structure.

The team estimates that the inner ring extends from about 100,000 to 240,000 kilometres from the star, while the outer ring runs from roughly 375,000 kilometres to more than 1.3 million kilometres. Observations made between 2021 and 2023 indicate that the structure remained stable for more than two years. The researchers identified calcium, oxygen, magnesium and iron in the gas. They found much more magnesium in the inner ring, which they say could mean the debris came from two different planetary bodies or from separate layers of one body.

The team proposes that two surviving bodies orbit within the rings and help maintain the gap. Its models suggest the inner body may be no larger than an asteroid a few kilometres across, while the outer body could be as large as Pluto or the Moon. “It hints that dead stars can have disc structures far more complex than previously realised,” said Felipe Lagos-Vilches of the University of Warwick. White dwarfs are the dense cores left when stars like the Sun run out of fuel, making the system relevant to studies of how planetary systems change as their stars age.