The central object of the system is the white dwarf J1328−1450, the dense, burnt-out core left behind when a star similar to our Sun ran out of fuel. As stars like the Sun enter the final stages of their lives, they expand and shed their outer layers, engulfing and destroying nearby planets. Any surviving rocky bodies can then break apart, forming a disc of rubble around the central dead star. Discs of this kind have been seen before around white dwarfs, but the one surrounding J1328−1450 is different: instead of a single ring of vaporised planetary rubble, the star is encircled by two concentric debris rings.

“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,” says Nicola Gentile Fusillo, an astronomer at the Università degli Studi di Trieste in Italy and lead author of the study, published this week in Nature Astronomy.

The discovery was made with the X-Shooter instrument on ESO’s Very Large Telescope, located in Chile’s Atacama Desert. All previously known debris discs around white dwarfs have been identified by the same observational signature, which indicates the presence of a single, flat, rotating disc. The new observations show that the J1328−1450 system breaks this pattern completely, revealing instead the unique fingerprint of a double disc. Using X-Shooter, the astronomers measured the speed of the gas orbiting the white dwarf and found that it moves at two distinct speeds — a clear indication that the gas is distributed in two concentric discs with a gap in between.

According to the research team, this complex double structure is most likely maintained by two surviving planet-like bodies on separate orbits. The researchers estimate that the body feeding the inner ring is the size of a typical asteroid, only a few kilometres in diameter, while the outer one could be as large as Pluto, or even our Moon. As these two planetesimals orbit the white dwarf, they interact with dust grains in the disc, releasing gas in the process. The most likely explanation is that these two gaseous discs are maintained by the two surviving bodies, whose continued presence sculpts and sustains the remarkable double-ring architecture.

“The structure we see in this system is particularly intriguing because the two gaseous rings are remarkably stable and remain separated by a gap,” says co-author Felipe Lagos-Vilches, an astronomer at the University of Warwick in the United Kingdom and at 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,” he adds.

The observations also reveal the chemical makeup of the disc in striking detail. Elements such as calcium, oxygen, magnesium and iron are present, indicating a composition similar to that of the rocky planetary material found in our own Solar System. More remarkably, the data indicate that the two rings have rather different compositions: the inner ring is rich in magnesium gas, while the outer ring is largely stripped of it. This chemical contrast suggests that the planetesimals feeding the rings originated from two parent planets with different compositions. An alternative explanation, the team notes, is that the two rings are fed by different parts of a single celestial body — for example, the crust and the core of a differentiated planet — each contributing its own distinctive chemical signature to the debris it sheds.

“It hints that dead stars can have disc structures far more complex than previously realised,” adds Gentile Fusillo, who is also affiliated with the INAF-Astronomical Observatory of Trieste. The finding expands the known diversity of white dwarf debris systems and demonstrates that the aftermath of planetary destruction around dead stars can be far more intricate than the single flat disc that astronomers had grown accustomed to detecting.

The discovery also carries a message closer to home. Our Solar System could meet a similar end, because our Sun will, in the far future, become a white dwarf in a process that may destroy Earth. Long before that, the Sun will expand and shed its outer layers, just as the progenitor star of J1328−1450 did, threatening the inner planets while more distant bodies may survive and eventually break apart into debris. “The system therefore offers a remarkable glimpse of what the future of planetary systems, including systems like our own, might look like,” concludes Lagos-Vilches.

The research was presented in a paper published in Nature Astronomy, authored by Nicola Pietro Gentile Fusillo of the University of Trieste and the INAF-Astronomical Observatory of Trieste, Felipe Lagos-Vilches of the University of Warwick and the Universidad Técnica Federico Santa María, Boris T. Gänsicke of the University of Warwick, Christopher J. Manser of Imperial College London, and Detlev Koester of the University of Kiel. For now, the double disc around J1328−1450 stands as the first observed example of its kind — a snapshot of planetary wreckage, held in place by two surviving remnants, around a star that once may have resembled our own Sun.

Subject of Research: A double debris disc of vaporised planetary material around the white dwarf J1328−1450, apparently maintained by two surviving planetesimals

Article Title: Dead star and planetary bodies: astronomers spot unique disc of debris that foretells Solar System’s future

Article References: Dead star and planetary bodies: astronomers spot unique disc of debris that foretells Solar System’s future. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: white dwarf, debris disc, J1328−1450, ESO Very Large Telescope, X-Shooter, planetesimals, planetary system evolution, stellar death, Nature Astronomy, magnesium, rocky planets, Solar System future