An international team of astronomers believes they may have witnessed the birth of a black hole or an incredibly powerful neutron star for the first time.
The cosmic event occurred in June last year and was picked up by telescopes in Hawaii. It happened in a dwarf galaxy called CGCG 137-068, located about 200 million light-years away in the Hercules constellation. The event was witnessed as a bright burst.
Initially, scientists suspected it to be a supernova, but after detailed investigation, they concluded that there was no possibility of it being a supernova event.
According to the research team, the burst was about 10 to 100 times brighter than most supernovas. Moreover, the object dubbed AT2018cow or 'The Cow' reached its peak brightness within days, much faster than other supernovas. It faded away much quickly, and it emitted most of its power in just two weeks' time.
It was surely something that scientists had never seen before, and they wanted to solve the mystery quickly.
The research team used the WM Keck Observatory on Maunakea, Hawaii and ATLAS twin telescopes at the University of Hawaii Institute for Astronomy to study the 'The Cow' in detail. They examined the object at different wavelengths, using radio waves, gamma rays, hard x-rays, and soft x-rays (which are much more powerful than ordinary x-rays).
The team found that the 'ejecta' swirling around 'The Cow' was about 10 times less, compared to a typical stellar explosion. This allowed astronomers to see directly through to the object's central engine's radiation. The observations enabled them to conclude that the object was most likely a forming black hole or neutron star.
"Based on its X-ray and UV emission, The Cow may appear to have been caused by a black hole devouring a white dwarf," said Raffaella Margutti, assistant professor of physics and astronomy at Northwestern University and lead author of the study.
"But further observations of other wavelengths across the spectrum led to our interpretation that The Cow is actually the formation of an accreting black hole or neutron star."
The team also believes that the star's relative closeness to Earth helped them track the event in detail.
"Two hundred million light-years is close for us," said Margutti. "This is the closest transient object of this kind that we have ever found."
The findings of the study are published in the Astrophysical Journal.
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