Physicists often turn to the Rayleigh-Taylor instability to clarify why fluid structures form in plasmas, but that might not be the complete story with regards to the ring of hydrogen clumps around supernova 1987A, research from the University of Michigan suggests.
In a study published in Physical Review Letters, the team argues that the Crow instability does a greater job of explaining the “string of pearls” encircling the remnant of the star, shedding light on a longstanding astrophysical mystery.
“The fascinating part about that is that the identical mechanism that breaks up airplane wakes might be in play here,” said Michael Wadas, corresponding creator of the study and a graduate student in mechanical engineering on the time of the work.
In jet contrails, the Crow instability creates breaks in the sleek line of clouds due to the spiraling airflow coming off the tip of every wing, often called wingtip vortices. These vortices flow into each other, creating gaps — something we will see due to the water vapor within the exhaust. And the Crow instability can do something that Rayleigh-Taylor couldn’t: predict the variety of clumps seen across the remnant.
“The Rayleigh-Taylor instability could let you know that there could be clumps, however it can be very difficult to drag a number out of it,” said Wadas, who’s now a postdoctoral scholar on the California Institute of Technology.
Supernova 1987A is amongst probably the most famous stellar explosions since it’s relatively near Earth at 163,000 light years away, and its light reached Earth at a time when sophisticated observatories existed to witness its evolution. It’s the primary supernova visible to the naked eye since Kepler’s supernova in 1604, making it an incredibly rare astrophysical event that has played an outsized role in shaping our understanding of stellar evolution.
While much continues to be unknown concerning the star that exploded, it’s believed that the ring of gas surrounding the star ahead of the explosion got here from the merger of two stars. Those stars shed hydrogen into the space around them as they became a blue giant tens of 1000’s of years before the supernova. That ring-shaped cloud of gas was then buffeted by the stream of high-speed charged particles coming off the blue giant, often called a stellar wind. The clumps are believed to have formed before the star exploded.
The researchers simulated the way in which the wind pushed the cloud outward while also dragging on the surface, with the highest and bottom of the cloud being pushed out faster than the center. This caused the cloud to twist in on itself, which triggered the Crow instability and caused it to interrupt apart into fairly even clumps that became the string of pearls. The prediction of 32 could be very near the observed 30 to 40 clumps across the supernova 1987A remnant.
“That is an enormous piece of why we expect that is the Crow instability,” said Eric Johnsen, U-M professor of mechanical engineering and senior creator of the study.
The team saw hints that the Crow instability might predict the formation of more beaded rings across the star, further out from the ring that appears brightest in telescope images. They were pleased to see that more clumps seem to seem within the shot from the James Webb Space Telescope’s near-infrared camera, released in August last 12 months, Wadas explained.
The team also suggested that the Crow instability could be at play when the dust around a star settles into planets, although further research is required to explore this possibility.
The study was supported by the Department of Energy, with computing resources provided by the Extreme Science and Engineering Discovery Environment
Co-authors of the study are: William White and Aaron Towne, a graduate student and an assistant professor in mechanical engineering, respectively; and Heath LeFevre and Carolyn Kuranz, a research fellow and an associate professor of nuclear engineering and radiological sciences, respectively; all at U-M.
