Astronomers are in awe of a ‘never been witnessed before’ celestial spectacle known as the ‘Tasmanian devil’.
Elliot Nash
'Newsweek' reports that a spectacular night sky show might be in store for Earth as our stellar neighbor Betelgeuse nears its end. Approximately 650 light years from Earth, Betelgeuse has been growing increasingly bright, reaching 142% of its normal luminosity in May.
Astronomers have stumbled upon a cosmic enigma dubbed the ‘Tasmanian devil’ in the depths of the Universe.
The phenomenon, officially known as a Luminous Fast Blue Optical Transient (LFBOT), has defied the norms of celestial behaviour, captivating scientists with its unparalleled energy emissions, according to a report published in Nature.
LFBOTs are already recognised as rare and immensely powerful events, surpassing the might of supernovas.
However, the ‘Tasmanian devil’ LFBOT, observed on September 7, 2022, has rewritten the cosmic rule book.
Unlike its counterparts, this celestial spectacle didn’t adhere to the expected fade after its initial burst.
Instead, it continued to explode with supernova-like energies in rapid succession, defying the conventional timescales of such events.
Co-author of the paper, Professor Jeff Cooke from Swinburne University of Technology and the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav) led the observations using the W. M. Keck Observatory in Hawaii. Professor Cooke said an event like this has “never been witnessed before”.
The ‘Tasmanian devil’ emitted bursts of energy so intense they exceeded the combined output of an entire galaxy containing hundreds of billions of stars like our Sun.
Even more perplexing was that, contrary to expectations, the source briefly brightened again and again after its initial burst.
Cornell University Assistant Professor Anna Ho, lead author of the paper, said the ‘Tasmanian devil’ LFBOT, “a kind of weird, exotic event,” exhibited 14 irregular and highly energetic bursts over a 120-day period, captured by multiple observatories worldwide.
“However, these bursts are likely only a fraction of the total number,” Assistant Professor Ho said.
While the source of this astronomical spectacle remains shrouded in mystery, the current theory suggests the involvement of a black hole or neutron star formed by the initial explosion.
This celestial entity is believed to be collecting an immense amount of matter, leading to the subsequent intense bursts that have left astronomers in awe.
The observations were conducted by the W. M. Keck Observatory, as part of a global initiative involving 15 observatories.
“These (studies) are important to help understand the nature of this source, how these massive stars transition during their death process, and to help find more events to understand how common they are in the Universe,” Prof Cook said.
ASHLEY STRICKLAND, CNN
November 16, 2023
Space is full of extreme phenomena, but the “Tasmanian devil” may be one of the weirdest and rarest cosmic events ever observed.
Months after astronomers witnessed the explosion of a distant star, they spotted something they have never seen before: energetic signs of life releasing from the stellar corpse about 1 billion light-years from Earth. The short, bright flares were just as powerful as the original event that caused the star’s death.
Astronomers dubbed the celestial object the “Tasmanian devil,” and they observed it exploding repeatedly following its initial detection in September 2022.
But the initial stellar explosion that caused the star’s death wasn’t any typical supernova, an increasingly bright star that explodes and ejects most of its mass before dying. Instead, it was a rare type of explosion called a luminous fast blue optical transient, or LFBOT.
LFBOTs shine brightly in blue light, reaching the peak of their brightness and fading within days, while supernovas can take weeks or months to dim. The first LFBOT was discovered in 2018, and astronomers have been trying to determine the cause of the rare cataclysmic events since.
But the Tasmanian devil is revealing more questions than answers with its unexpected behavior.
While LFBOTs are unusual events, the Tasmanian devil is even stranger, causing astronomers to question the processes behind the repetitive explosions.
“Amazingly, instead of fading steadily as one would expect, the source briefly brightened again — and again, and again,” said lead study author Anna Y.Q. Ho, assistant professor of astronomy in Cornell University’s College of Arts and Sciences, in a statement. “LFBOTs are already a kind of weird, exotic event, so this was even weirder.”
The findings about the latest Tasmanian devil LFBOT discovery, officially labeled AT2022tsd and observed with 15 telescopes around the globe, published Wednesday in the journal Nature.
“(LFBOTs) emit more energy than an entire galaxy of hundreds of billions of stars like the Sun. The mechanism behind this massive amount of energy is currently unknown,” said study coauthor Jeff Cooke, a professor at Australia’s Swinburne University of Technology and the ARC Centre of Excellence for Gravitational Wave Discovery, in a statement. “But in this case, after the initial burst and fade, the extreme explosions just kept happening, occurring very fast — over minutes, rather than weeks to months, as is the case for supernovae.”
Tracking the Tasmanian devil
Software written by Ho initially flagged the event. The software sifts through a half-million transients detected daily by the Zwicky Transient Facility in California, which surveys the night sky. Ho and her collaborators at different institutions continued to monitor the explosion as it faded and reviewed the observations a few months later. The images showed intense bright spikes of light that soon vanished.
“No one really knew what to say,” Ho said. “We had never seen anything like that before — something so fast, and the brightness as strong as the original explosion months later — in any supernova or FBOT (fast blue optical transient).
We’d never seen that, period, in astronomy.”
To better understand the quick luminosity changes occurring in the Tasmanian devil, Ho and her colleagues reached out to other researchers to compare observations from multiple telescopes.
Anna Ho developed the software that detected signs of life flaring from a stellar corpse. - Jason Koski/Cornell University
Altogether, the 15 observatories, including the high-speed camera ULTRASPEC mounted on the 2.4-meter Thai National Telescope, tracked 14 irregular light pulses over 120 days, which is likely just a fraction of the total number of flares released by the LFBOT, Ho said.
Some of the flares only lasted tens of seconds, which to astronomers suggests that the underlying cause is a stellar remnant formed by the initial explosion — either a dense neutron star or a black hole.
“This settles years of debate about what powers this type of explosion, and reveals an unusually direct method of studying the activity of stellar corpses,” Ho said.
Either object is likely taking on large amounts of matter, which fuels the subsequent bursts.
“It pushes the limits of physics because of its extreme energy production, but also because of the short duration bursts,” Cooke said. “Light travels at a finite speed. As such, how fast a source can burst and fade away limits the size of a source, meaning that all this energy is being generated from a relatively small source.”
If it’s a black hole, the celestial object may be ejecting jets of material and launching them across space at near the speed of light.
Another possibility is that the initial explosion was triggered by an unconventional event, such as a star merging with a black hole, which could present “a completely different channel for cosmic cataclysms,” Ho said.
The afterlife of stars
Studying LFBOTs could reveal more about the afterlife of a star, rather than just its life cycle that ends with an explosion and a remnant.
“Because the corpse is not just sitting there, it’s active and doing things that we can detect,” Ho said. “We think these flares could be coming from one of these newly formed corpses, which gives us a way to study their properties when they’ve just been formed.”
Astronomers will keep surveying the sky for LFBOTs to see how common they are and uncover more of their secrets.
“This discovery teaches us more about the varied ways in which stars end their lives and the exotica that inhabit our Universe,” said study coauthor Vik Dhillon, professor in the department of physics and astronomy at the University of Sheffield in the United Kingdom, in a statement.
With unprecedented flares, stellar corpse shows signs of life
Peer-Reviewed PublicationAfter a distant star’s explosive death, an active stellar corpse was the likely source of repeated energetic flares observed over several months – a phenomenon astronomers had never seen before, a Cornell-led team reports in new research published Nov. 15 in Nature.
The bright, brief flashes – as short as a few minutes in duration, and as powerful as the original explosion 100 days later – appeared in the aftermath of a rare type of stellar cataclysm that the researchers had set out to find, known as a luminous fast blue optical transient, or LFBOT.
Since their discovery in 2018, astronomers have speculated about what might drive such extreme explosions, which are far brighter than the violent ends massive stars typically experience, but fade in days instead of weeks. The research team believes the previously unknown flare activity, which was studied by 15 telescopes around the world, confirms the engine must be a stellar corpse: a black hole or neutron star.
“We don’t think anything else can make these kinds of flares,” said Anna Y. Q. Ho, assistant professor of astronomy in the College of Arts and Sciences. “This settles years of debate about what powers this type of explosion, and reveals an unusually direct method of studying the activity of stellar corpses.”
Ho is the first author of “Minutes-duration Optical Flares with Supernova Luminosities,” published with more than 70 co-authors who helped characterize the LFBOT officially labeled AT2022tsd and nicknamed “the Tasmanian devil,” and the ensuing pulses of light seen roughly a billion light years from Earth.
Ho wrote the software that flagged the event in September 2022, while sifting through a half-million changes, or transients, detected daily in an all-sky survey conducted by the Califrnia-based Zwicky Transient Facility.
Then in December 2022, while routinely monitoring the fading explosion, Ho and collaborators Daniel Perley of Liverpool John Moores University in England, and Ping Chen of the Weizmann Institute of Science in Israel, met to review new observations conducted and analyzed by Ping – a set of five images, each spanning several minutes. The first showed nothing, as expected, but the second picked up light, followed by an intensely bright spike in the middle frame that quickly vanished.
“No one really knew what to say,” Ho recalled. “We had never seen anything like that before – something so fast, and the brightness as strong as the original explosion months later – in any supernova or FBOT. We’d never seen that, period, in astronomy.”
To further investigate the abrupt rebrightening, the researchers engaged partners who contributed observations from more than a dozen other telescopes, including one equipped with a high-speed camera. The team combed through earlier data and worked to rule out other possible light sources. Their analysis ultimately confirmed at least 14 irregular light pulses over a 120-day period, likely only a fraction of the total number, Ho said.
“Amazingly, instead of fading steadily as one would expect, the source briefly brightened again – and again, and again,” she said. “LFBOTs are already a kind of weird, exotic event, so this was even weirder.”
Exactly what processes were at work – perhaps a black hole funneling jets of stellar material outward at close to the speed of light – continues to be studied. Ho hopes the research advances longstanding goals to map how stars’ properties in life may predict the way they’ll die, and the type of corpse they produce.
In the case of LFBOTs, rapid rotation or a strong magnetic field likely are key components of their launching mechanisms, Ho said. It’s also possible that they aren’t conventional supernovas at all, instead triggered by a star’s merger with a black hole.
“We might be seeing a completely different channel for cosmic cataclysms,” she said.
The unusual explosions promise to provide new insight into stellar lifecycles typically only seen in snapshots of different stages – star, explosion, remnants – and not as part of a single system, Ho said. LFBOTs may present an opportunity to observe a star in the act of transitioning to its afterlife.
“Because the corpse is not just sitting there, it’s active and doing things that we can detect,” Ho said. “We think these flares could be coming from one of these newly formed corpses, which gives us a way to study their properties when they’ve just been formed.”
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JOURNAL
Nature
ARTICLE TITLE
Minutes-duration Optical Flares with Supernova Luminosities
ARTICLE PUBLICATION DATE
15-Nov-2023
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