Black holes continue to “burp” stars they destroyed years before — and astronomers have no idea why

Black holes are among the most talked about objects in the universe, yet scientists still have so much to learn when it comes to understanding their mysterious behavior.

We already know that the notoriously messy eaters will gobble up anything that gets in their way.

But what astronomers didn’t realize was that the cosmic monsters then “ejected” an eclectic mix of stars, gas, planets, and dust that they had destroyed years earlier.

This surprise only came to light when experts decided to monitor black holes for several years after they were involved in tide disruption events (TDEs).

Traditionally, objects have only been studied for a few months after a TDE — what happens when stars get too close to a black hole and are blown to pieces in a process called spaghettiification.

Mysterious: Scientists know that black holes are notoriously messy eaters, devouring everything in their path. What they didn’t realize, however, is that the cosmic monsters were “belching up” a mixture of stars, gas, planets and dust that they had destroyed years earlier (stock image)

Although black holes cannot be observed directly, scientists can observe a TDE because these events emit light, radio, and other waves for up to a few weeks or months as they occur.

In the process, some of the gas and dust left over from a shattered star is ejected from the black hole.

The rest then forms a thin Frisbee-like structure around itself, a so-called accretion disk, which gradually feeds the stellar material towards the black hole.

However, scientists at the Harvard and Smithsonian Center for Astrophysics have found that some of this material can resurface in between two and six years after a TDE.

They found that up to half of the 24 black holes they observed later had “burp” seizures, although they have no idea why.

“If you look years later, a very, very large fraction of these black holes that have no radio emission at this early point in time will actually suddenly ‘turn on’ radio waves,” lead author Yvette Cendes told Live Science.

“I call it a ‘burp’ because we have a kind of lag where this material doesn’t come out of the accretion disk until much later than people expected.”

Although black holes cannot be observed directly, scientists can observe a TDE because these events emit light, radio, and other waves for up to a few weeks or months as they occur

The question is, where is it stored before it’s “belched” again?

Scientists know for sure that it’s not coming from inside a black hole, because the objects have an event horizon where gravity is so strong that even light can’t escape.

Cendes added: “We do not fully understand whether the material observed in radio waves originates from the accretion disk or whether it is stored somewhere near the black hole.”

“However, black holes are definitely messy eaters.”

The researchers plan to continue monitoring the black holes they observe, especially as some of them continue to get brighter after TDE.

They are also calling for improved computer modeling to better represent how black holes can “belch” years later, which experts say will improve understanding of this strange behavior.

The new research has been published in the arXiv preprint database but has not yet been peer-reviewed.