A dying star is shedding a massive sphere of dust and gas approximately half the size of our solar system. Astronomers are puzzled by this phenomenon as there’s no known process capable of producing such an extensive amount of material from a single star.

Red supergiants are the universe’s largest stars, representing the final stages of a massive star that has exhausted most of its fuel before it eventually goes supernova. During this brief phase, the star expands rapidly, releasing copious amounts of gas and dust and forming bubbles around it.

Mark Siebert from the Chalmers Institute of Technology in Sweden and his colleagues found that the red supergiant star DFK 52 possesses the largest known environment for such celestial bodies, creating a bubble 50,000 times wider than the distance between Earth and the Sun. Curiously, these stars are relatively dim, suggesting they have less energy than what would typically be needed to generate such a vast debris field. “I can’t ascertain how I can disperse so much material in that timeframe,” Siebert remarks.

Previously, DFK 52 had been observed by various telescopes, allowing astronomers to conclude that it expelled a normal quantity of gas. However, when Siebert and his team used the Atacama Large Millimeter Array (ALMA) in Chile, they detected light at longer wavelengths from older, much cooler materials.

“It reveals an extensive environment around DFK 52 with a very complex geometry that’s not entirely understood yet,” Siebert explains. “We don’t grasp the precise structure, but we acknowledge its immense scale.”

Similar to the intricate flow of bubbles throughout the structure, Siebert and his team observed ring-like formations at the core of the overall sphere, expanding at approximately 30 kilometers per second. They estimate that this activity likely stemmed from a significant event that occurred around 4,000 years ago, potentially key to understanding how the star generated so much material.

A potential explanation for the extensive environment is that these stars may have briefly increased in brightness and then dramatically faded, although red supergiants are not typically known for such fluctuations, according to Siebert. Alternatively, another star may be orbiting a larger star, stripping material from DFK 52, but this would likely result in a more symmetrical bubble, Siebert asserts. “It is evident that some additional energy sources must contribute to this phenomenon, but we remain uncertain about what they are,” he comments.

“The explosion won’t alter the star’s overall evolution, but it may significantly influence the future appearances of supernovas,” says Emma Beads from John Moores University, Liverpool, UK. “This is an intriguing development that enhances our understanding of unusual supernovae.”

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