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BY MARK WORGAN

Astronomers have discovered an unusual double disc of planetary debris orbiting a dead star, offering a tantalising clue as to how our own solar system may look one day.

The discovery, made using the European Southern Observatory’s Very Large Telescope (VLT) in Chile, reveals two distinct rings of material separated by a clear gap.

Scientists believe the structure is being shaped by two surviving planet-like bodies, one of which could be as large as Pluto or even the Moon.

The debris consists of the remains of planets that once orbited the star, known as J1328−1450, a white dwarf — the dense, burnt-out core left behind when a star similar to the Sun runs out of fuel.

The findings, published in Nature Astronomy, provide the first known example of a complex double debris disc around a white dwarf, potentially shaped by two surviving planetary bodies.

“We have known for some time that planets may survive beyond the transformation of their central star, but this is the first example of a complex system with a double debris disc and potentially two surviving planetesimals,” said Nicola Gentile Fusillo, an astronomer at the University of Trieste in Italy and lead author of the study.

When stars like the Sun approach the end of their lives, they expand dramatically and shed their outer layers. In the process, they can engulf and destroy nearby planets.

Some rocky planetary bodies may survive, although they can subsequently break apart, creating discs of debris around the stellar remnant.

Previously identified debris discs around white dwarfs have generally appeared as single, flat, rotating structures.

But observations of J1328−1450 using the X-Shooter instrument on the VLT have revealed something different: two concentric rings of gaseous material, with a distinct gap between them.

“The structure we see in this system is particularly intriguing because the two gaseous rings are remarkably stable and remain separated by a gap,” said co-author Felipe Lagos-Vilches, an astronomer at the University of Warwick in the UK and the Universidad Técnica Federico Santa María in Chile.

“The system is a rare glimpse of the violent, chaotic process by which a planetary system meets its end, and it hints that dead stars can have disc structures far more complex than previously realised,” added Gentile Fusillo, who is also affiliated with the INAF-Astronomical Observatory of Trieste.

The researchers believe the unusual arrangement is probably maintained by two surviving planet-like bodies, each orbiting at a different distance from the white dwarf.

Their estimates suggest the body associated with the inner ring is comparable to a typical asteroid, measuring a few kilometres across.

The object linked to the outer ring could be considerably larger, potentially reaching the size of Pluto or even Earth's Moon.

The observations also revealed the presence of calcium, oxygen, magnesium and iron in the debris, suggesting it originated from rocky planetary material similar to that found in our own Solar System.

However, the two rings appear to have different chemical compositions.

The inner ring contains relatively large amounts of magnesium gas, while the outer ring has largely been stripped of the element.

This difference could mean the material came from two planets with distinct compositions. Another possibility is that the debris originated from different layers of a single planetary body, such as its crust and core.

The discovery challenges previous assumptions about the structures that can form around dead stars and suggests that planetary systems may leave behind more complex remnants than astronomers had realised.

The findings also offer clues about the distant future of our own Solar System.

In several billion years, the Sun is expected to expand into a red giant before shedding its outer layers and eventually becoming a white dwarf.

The expansion is likely to destroy Earth, although some more distant objects and planetary material could survive the transformation.

The system around J1328−1450 may therefore provide a rare opportunity to study what remains after a star's death and how surviving planetary bodies interact with the debris around them.

“The system therefore offers a remarkable glimpse of what the future of planetary systems, including systems like our own, might look like,” Lagos-Vilches said.