The “Tasmanian Devil” is a stellar corpse that shows signs of active life

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Space is full of extreme phenomena, but the Tasmanian Devil may be one of the strangest and rarest cosmic events ever observed.

After months of watching a distant star explode, astronomers have discovered something they’ve never seen before: vital signs of life emanating from a stellar corpse about a billion light-years from Earth. The short, bright flares were just as powerful as the original event that caused the death of the star.

Astronomers named the celestial body the “Tasmanian Devil,” and observed its explosion repeatedly after its initial discovery in September 2022.

But the initial stellar explosion that caused the star’s death was not any typical supernova: a star that grows brighter, explodes, and expels most of its mass before dying. Instead, it was a rare type of outburst called Fast Blue Optical Transient, or LFBOT.

LFBOTs shine brightly in blue light, reaching peak brightness and fading within days, while supernovae can take weeks or months to dim. the The first LFBOT was discovered in 2018Astronomers have been trying to determine the cause of the rare catastrophic events ever since.

But the Tasmanian Devil reveals more questions than answers with its unexpected behavior.

While LFBOTs are unusual events, the Tasmanian Devil is even stranger, leading astronomers to question the processes behind the frequent eruptions.

“Surprisingly, instead of fading steadily as expected, the source brightened briefly over and over again,” lead study author Anna Y. Kew Ho, an assistant professor of astronomy in Cornell University’s College of Arts and Sciences, said in a statement. “LFBOTs are already kind of weird and weird events, so this was even weirder.”

The findings related to the latest discovery of the Tasmanian Devil LFBOT, officially named AT2022tsd and observed using 15 telescopes around the world, were published on Wednesday in the journal. nature.

“(LFBOTs) emit more energy than an entire galaxy made up of hundreds of billions of stars like the Sun. The mechanism is “What lies behind this enormous amount of energy is currently unknown.” “But in this case, after the initial explosion and dissipation, intense explosions continued to occur, and they occurred very quickly — over the course of minutes, not weeks to months, as in supernovae.” .

The program written by Ho initially flagged the event. The program examines the half-million transients detected daily by the Zwicky Transient Facility in California, which scans the night sky. She and her collaborators at various institutions continued to monitor the explosion as it faded, and they reviewed the notes a few months later. The images showed intense, bright spikes of light that quickly disappeared.

“Nobody really knew what to say,” he said. “We’ve never seen anything like this before — something so fast, and as bright as the original explosion months later — in any supernova or FBOT (fast blue optical transient).”
“We have never seen this before in astronomy.”

To better understand the rapid changes in brightness occurring in the Tasmanian devil, she and her colleagues reached out to other researchers to compare observations from multiple telescopes.

In all, the 15 observatories, including the ULTRASPEC high-speed camera mounted on the 2.4-meter Thai National Telescope, tracked 14 irregular light pulses over 120 days, which likely represents a small fraction of the total number of flares fired by LFBOT , he. He said.

Some flares lasted only tens of seconds, which suggests to astronomers that the underlying cause is stellar remnants formed from the initial explosion — either a dense neutron star or a black hole.

“This resolves years of debate about what fuels this type of explosion, and reveals an unusually direct way to study the activity of stellar bodies,” Hu said.

Either object would likely take up large amounts of matter, fueling subsequent explosions.

“It pushes the limits of physics because of its excessive energy production, but also because of its short-duration explosions,” Cook said. “Light travels at a finite speed. As such, how quickly a source explodes and vanishes limits the size of the source, meaning all this energy is generated from a relatively small source.

If it were a black hole, the celestial body might eject jets of material and shoot them through space at close to the speed of light.

Another possibility is that the initial explosion was caused by an unconventional event, such as a star merging with a black hole, which could offer a “completely different conduit for cosmic catastrophe,” Ho said.

Studying LFBOTs could reveal more about the afterlife of a star, rather than just its life cycle that ends in an explosion and remnant.

“Because the body is not just sitting there, it is active and doing things that we can detect,” Ho said. “We think these flares could come from one of these newly formed bodies, giving us a way to study their properties when they were just forming.”

Astronomers will continue scanning the skies for LFBOTs to find out how common they are and uncover more of their secrets.

“This discovery teaches us more about the diverse ways in which stars end their lives, and the strange objects that inhabit our universe,” said study co-author Vic Dillon, a professor in the Department of Physics and Astronomy at the University of Sheffield in the United Kingdom. a permit.