Astronomers Spot Dead Star Unexpectedly Come to Life With Powerful Flashes

A bizarre series of energetic flares in deep space may have been caused by the reanimated corpse of a star, scientists have found.

A hundred days after a huge stellar explosion known as a luminous fast blue optical transient (LFBOT), astronomers spotted several bright flashes, each only lasting a few minutes, and as powerful as the original explosion.

In the years since these flashes were spotted by telescopes around the world in 2018, scientists have been mystified as to what may have caused them. Now they think it could be the remnants of a dead star in the form of a black hole or neutron star, according to a new study in the journal Nature.

"Some of the flares were as powerful as the original LFBOT, which means they were even more powerful than a supernova!" Anna Y. Q. Ho, assistant professor of astronomy in the Cornell College of Arts and Sciences, told Newsweek. "We've never seen anything with this combination of duration, power, and wavelength, let alone in the aftermath of a mysterious cosmic cataclysm (the LFBOT itself). The "engine" of these flares was almost certainly a neutron star or a black hole."

The original LFBOT, named AT2022tsd and nicknamed "the Tasmanian devil," was a special type of stellar explosion that is very short-lived and energetic, with the scientists being unclear as to this one's origin. It is thought to be situated around a billion light-years from Earth.

"LFBOTs differ from normal supernovae in several ways. In particular, they look quite different: their light is much more powerful than the light from supernovae, across most of the electromagnetic spectrum (X-rays, radio, optical, ultraviolet)," Ho said. "We primarily discover them using optical light, and in that part of the electromagnetic spectrum, their signal is much faster—whereas normal supernovae brighten and fade over weeks to months, LFBOTs brighten and fade significantly over just a few days."

Unlike regular supernovas, which flare brightly and then fade away, LFBOTs can remain active for longer. The scientists observed 14 irregular light pulses over a 120-day period coming from the Tasmanian devil, and think that these may represent only a fraction of the total number emitted from the explosion.

"Even though normal supernovae are thought to involve the formation of a neutron star or black hole, we usually don't see a significant signal from that newly formed "corpse." In LFBOTs, that object remains very active for a long time—up to hundreds of days," Ho said.

The extended activity of LFBOTs is thought to be caused by stellar corpses in the form of black holes or neutron stars, which may also be driving the observed flares from the Tasmanian devil.

"[There are] two possibilities [as to why a black hole or neutron star may be causing the flares]. Possibility A is that the object formed in the LFBOT—that it's a corpse of an explosion, like the death of a star. Possibility B is that the object was already there, and that the LFBOT activated it. For example, the object could have gotten close enough to a star to shed it, creating a sort of "explosion" (the LFBOT) and then, for hundreds of days, the remnants of the star falling onto the object could have powered an outflow and these flares."

Exactly what powers LFBOTs in general is still a mystery to the scientists, with the authors of the paper hoping to further research what causes stars to die in certain ways and behave the way they do after death.

"We might be seeing a completely different channel for cosmic cataclysms," Ho said in a statement.

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.

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