Three years after eating a star, a black hole has been observed ejecting debris, which astronomers liken to a cosmic burp.

Typically, this type of occurrence would be observed during the event, and Harvard University experts have yet to determine the cause of the delay.

After it swallowed the tiny star in 2018, they observed the black hole for several months before deciding to revisit it in 2021.

Then, they discovered radio waves suddenly erupting from it, as if it were “vomiting forth a quantity of debris from the star it consumed years earlier.”

Yvette Cendes, a research associate at the Center for Astrophysics and the study’s principal author, stated, “This caught us off guard.

“No one has ever witnessed anything similar to this before,”

When a star approaches a black hole too closely, it undergoes’s paghettification,’ in which it is stretched vertically and compressed horizontally by the black hole’s powerful gravitational field.

These are known as tidal disruption events or TDEs, and when they occur, they are recognized for generating light.

This is because the material finally spirals around the black hole and warms up, producing a flash that astronomers can detect millions of light years away.

In addition, some of the matter that the black hole cannot eat is occasionally ejected back into space.

This is known as an “outflow” and often happens shortly after a TDE, not years later.

In October 2018, astronomers observed a TDE 665 million light-years away from Earth, designated AT2018hyz.

However, co-author Sebastian Gomez deemed it unimpressive because the mass of the star was barely one-tenth that of the sun.

He stated, “We observed AT2018hyz in visible light for several months until it disappeared, and then we forgot about it.”

In June 2021, the team located in the United States decided to revisit several TDEs that had occurred in the preceding years, notably AT2018hyz.

Radio data from New Mexico’s Very Large Array revealed that the black hole had strangely reawakened.

Edo Berger, co-author, and professor of astronomy commented, ‘We have been investigating TDEs with radio telescopes for more than a decade, and we occasionally find that they emit radio waves when they spew out debris as the star is being engulfed by the black hole.

In AT2018hyz, however, there was radio silence for the first three years, and it has now become one of the most radio-bright TDEs ever detected.

Using telescopes in Chile, South Africa, Australia, and space, they conducted studies of the TDE at numerous wavelengths of light.

Scientists report that the black hole has not consumed anything fresh in the three years since the original star, although the reason for the delay in the outflow is unknown.

In an article published in the Astrophysical Journal, the researchers show that the material is moving at a speed equal to fifty percent of the speed of light.

Cendes states that the majority of TDEs have outflows that travel at 10% of the speed of light.

Cendes likens the feeding behavior of black holes to ‘burping’ after a meal, and they believe that their findings will expand knowledge of this phenomenon.

Berger states, “This is the first time we have experienced such a long wait between the feeding and the outflow.”

The next step is to see if this is a common occurrence and if we have simply not been examining TDEs late enough in their evolution.