Dead Star Found With Two Debris Rings, A First-Ever Cosmic Setup

Double Rings Around a Dead Star Hint at Hidden Objects

Astronomers have found something no one has ever seen before: a dead star circled by two separate rings of glowing gas instead of just one. The pattern points to two rocky objects, possibly anywhere from asteroid-sized to Pluto-sized, lurking in the wreckage, each helping maintain its own ring. Nobody has spotted either one yet.

Cataloged as WD J1328-1450 and sitting about 1,600 light-years away, the star is a white dwarf, the compact, burned-out core left behind when a star like the sun runs out of fuel and sheds its outer layers. That is the fate expected for the sun itself. Astronomers already knew of 21 other white dwarfs with glowing rings of planetary rubble, and every one showed a single ring. This one broke the pattern.

There’s a second twist: the rings don’t match. The inner one gives off the glow of magnesium, a metal common in rock, while the outer one doesn’t, even though calcium and oxygen show up in both. Reported in Nature Astronomy, the discovery complicates scientists’ ideas about how a dead star’s leftover debris settles into rings.

Four Light Peaks Point to Two Rings Around the Dead Star

Researchers first spotted the star because of an infrared glow, a telltale sign of orbiting dust. That dust shines unusually brightly, among the brightest of any published ring of this kind. They then aimed X-shooter, an instrument on the European Southern Observatory’s Very Large Telescope in Chile, at the star over several observing sessions between 2021 and 2023. The sample size was one star, watched closely.

Its light carried traces of calcium, magnesium, and silicon, elements that must have rained down from rocky debris. It also carried something new. A single ring of gas leaves two peaks in a star’s light, one from gas swinging toward Earth and one from gas swinging away. This star showed four. Two rings nested like a bullseye would explain it, each spinning at its own speed because they sit at different distances from the star.

Computer modeling placed both rings close in, with the outer edge reaching only about twice the sun’s radius from the star and a gap with no glowing gas between the two. The light pattern held steady across more than two years of observations, a sign of a lasting arrangement rather than a passing event.

Magnesium Shows Up in the Inner Ring but Not the Outer One

Magnesium gave the clearest sign that the rings differ. Had the outer ring matched the inner one’s makeup, the team calculated, its magnesium glow would have stood well above the background noise. It showed none.

That absence fits rings built from different material, either from two shattered objects or from separate layers of one broken-apart body, much as Earth’s crust and mantle have different chemistry.

Two Hidden Rocky Bodies Best Explain the White Dwarf’s Rings

Researchers weighed simpler options first. Two white dwarfs sitting too close together to tell apart, each with its own ring, seemed extremely unlikely, since only about 0.067 percent of white dwarfs have gas rings, making two at once a long shot. A single object carving a gap in one wide band of debris fared no better, because it would have no way to keep making gas for the rings on either side.

A third idea, a puffed-up band of debris casting a shadow on itself to mimic two rings, can’t be completely ruled out. But no existing theoretical model of white dwarf debris backs it, no other known gas ring around a white dwarf or a young star has shown this pattern, and nothing about this star looks unusual enough to explain why it alone would.

That left two surviving rocky bodies as the likeliest explanation. Gas has to keep forming steadily in two separate spots without the two rings smearing together, and a solid object in each ring, constantly interacting with dust, could do that.

One Hidden Object Near the Dead Star Could Be as Big as Pluto

Surviving that close to a white dwarf takes strength, since its gravity tears apart weak bodies. Using typical strength estimates for rock, the team calculated that the inner object is probably no bigger than a typical asteroid from the solar system’s asteroid belt. The outer object has more room. Depending on its position and makeup, it could range from Ceres, the largest asteroid in the solar system, up to Pluto or even the Moon, roughly 2,200 miles across at most. Those are size limits, not measurements.

Two rings around a dead star, each possibly held in place by its own surviving rocky object, would mean a star’s death can leave planetary wreckage in a messier, more layered shape than one tidy ring. Until astronomers actually spot those objects, though, WD J1328-1450 remains a strong clue, not a confirmed case.

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