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(Homeland) - Could it be that even cosmic black holes take years to 'digest' a star?
In October 2018, in a space region 665 million light-years away, a small star was torn into countless pieces as it approached a black hole. Although this fascinating event brought valuable research data, in reality, it happened as casually as a daily meal.
Nearly 3 years after the 'light meal,' the black hole once again shines in the sky, captivating the research community. However, this time the intriguing phenomenon is different, and from 2018 until now, the black hole has not swallowed any more stars.
'The phenomenon completely surprised us; no one has ever seen a similar event unfold,' said researcher Yvette Cendes, working at the Harvard-Smithsonian Center for Astrophysics and the main author of the new study.
According to the conclusions of the scientific team, matter ejected from the black hole is flying at half the speed of light. The research community is currently unclear why the black hole retains matter for several years before releasing it.
Under the guidance of Mr. Cendes, the data analysis team observed an unusual phenomenon of black holes regurgitating stars swallowed in recent years. According to the data collected by the Very Large Array (VLA), the black hole unexpectedly became active again in June 2021, immediately capturing global attention. Scientists named this black hole's 'eat and regurgitate' phenomenon AT2018hyz.
Synthesizing data on stars swallowed by black holes, along with numerous signals from observatories worldwide, scientists have confirmed an unprecedented phenomenon.
'We have been studying [events of stars being swallowed by black holes] with radio telescopes for over a decade, occasionally detecting radio waves emitted as the black hole spews out previously ingested matter,” said Edo Berger, a professor of astrophysics at Harvard University and co-author of the new report. 'But in the case of AT2018hyz, it has been silent for 3 years, and suddenly it lights up, becoming the brightest [black hole swallowing star] phenomenon in the radio telescope database ever collected.'
The phenomenon of black holes swallowing stars, scientifically known as Tidal Disruption Event (TDE), occurs when a star approaches a black hole and is engulfed. The stream of matter pouring out from the star will resemble spaghetti and simultaneously illuminate a corner of space. Subsequently, the matter will orbit the black hole at an extremely high speed, forming an accretion disk, visible even to observatories millions of light-years away.
Some star matter sucked into the black hole will be ejected out, scientists believe it's because the black hole is not tidy in its eating habits, causing matter to be scattered. However, the phenomenon of ejecting matter into space usually occurs shortly after the TDE event, not many years later like AT2018hyz. This is an unprecedented and exceptional case.
The speed of the ejected matter from the black hole reaches up to 50% of the speed of light. According to Professor Cendes, the majority of 'matter regurgitation' events only reach speeds equivalent to 1/10th of the speed of light.
'This is the first time we've witnessed such a prolonged gap between the ingestion and the ejection phase,' noted researcher Berger. 'The next step will be to investigate whether this phenomenon occurs more frequently or if we've just never seen a TDE regurgitate so late.'
According to Harvard.edu
