This Black Hole Burps Out Materials From Star It Devoured Three Years Ago

(Photo : NASA/Goddard Space Flight Center/CI Lab)

On March 28, 2011, NASA's Swift detected intense X-ray flares thought to be caused by a black hole devouring a star. In one model, illustrated here, a sun-like star on an eccentric orbit plunges too close to its galaxy's central black hole. About half of the star's mass feeds an accretion disk around the black hole, which in turn powers a particle jet that beams radiation toward Earth.

Astronomers discover a black hole 'burping out' remnants of the 'spaghettified' star it swallowed years ago, a phenomenon no astronomer has ever recorded before.

The Black Hole Eating A Star

Three years ago, October 2018, a black hole was detected chewing up a star that had traveled too near to it in a galaxy 665 million light-years away from Earth. Astronomers, who frequently watch these catastrophic collisions between stars and voracious black holes, were unsurprised by the incident.

These so-called 'Tidal disruption events or TDEs' occur when things like stars orbit black holes. The immense gravitational attraction they meet causes tidal forces that elongate the star in one way while suppressing it in the other, a form called "spaghettified."

There is, however, something unique about this TDE. Given that it hasn't eaten anything since this little star (roughly one-tenth the mass of the sun), the said black hole is now releasing material from its previous meal. Space.com reveals that exactly three years after being torn and consumed by a black hole, the celestial entity is lighting up the night sky with dramatic emissions as it burps up material from its cluttered cosmic supper.

The Black Hole Mystery

BGR reports that according to Yvette Cendes, a research associate at the Center for Astrophysics at Harvard & Smithsonian, the incident took them entirely off guard.

"It's as though this black hole had suddenly burped forth a large amount of material from the star it ate years before," Cendes added.

To explain it further, when this spaghettified material collides with the black hole, it warms up and produces a burst of light that astronomers can see from millions of light-years distant. The black hole occasionally shoots some of this star debris back into space. To put it another way, black holes are untidy eaters.

Cendes and her colleagues discovered that this material is being expelled from the black hole at a rate of nearly 300 million mph (480 million kph) - roughly half the speed of light. TDEs, on the other hand, often spew out this material at around 10% of the speed of light.

It's also unclear why this black hole took so long to digest its previous meal. This is the first time they have seen such a significant delay between feeding and outflow, according to co-author Edo Berger, an astronomy professor at Harvard University.

Berger stated that they have been watching TDEs with radio telescopes for more than a decade and occasionally glow in radio waves when they spew forth material as the black hole is eating the star. But, after three years of radio stillness, AT2018hyz has abruptly lighted up to become one of the most radio-luminous TDEs ever detected.

For now, the astronomers will look into whether the delay between feeding and emission is unique to AT2018hyz or a more typical occurrence that astronomers have overlooked.

"The next step is to explore whether this actually happens more regularly and we have simply not been looking at TDEs late enough in their evolution," Berger concluded.

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Written by Thea Felicity