- Astronomers made this discovery after spending years observing black holes
- Stars involved in tidal disturbance events are destroyed within hours
Black holes are among the most talked about objects in the universe, but scientists still have a lot to learn to understand their mysterious behavior.
We already know that notoriously messy eaters swallow everything in their path.
But what astronomers didn’t realize was that the cosmic monsters are then “burping up” an eclectic mix of stars, gas, planets and dust that they had destroyed years earlier.
This surprise only emerged because experts decided to monitor black holes for several years after they were involved in tidal disturbance events (TDEs).
Traditionally, objects were only studied a few months after a TDE, which occurs when stars venture too close to a black hole and are ripped apart in a process called spaghettification.
Mystery: Scientists know that black holes are notoriously messy eaters that gobble up everything in their path. But what they didn’t realize was that the cosmic monsters are ‘burping up’ a mixture of stars, gas, planets and dust they had destroyed years earlier (stock image)
WHAT IS A “TIDIAL DISTURBANCE EVENT”?
When a star gets too close to a black hole, it undergoes “spaghettification”, that is, it is stretched vertically and compressed horizontally by the strong gravitational field.
These are known as tidal disturbance events, or TDEs, and emit light, radio waves, and other waves for a few weeks or months during their occurrence.
Indeed, the elongated material eventually wraps around the black hole and heats up, creating a flash that astronomers can detect millions of light-years away.
Although black holes cannot be observed directly, scientists can observe a TDE because these events emit light, radio waves, and other waves for a few weeks or months when they occur.
When they occur, some of the remaining gas and dust from a destroyed star is thrown away from the black hole.
The remnant then forms a thin Frisbee-like structure around it, called an accretion disk, which gradually feeds this stellar material into the black hole.
But what scientists at the Harvard and Smithsonian Center for Astrophysics have discovered is that some of this material can then reappear between two and six years after a TDE.
They found that nearly half of the 24 black holes they observed burped, but they didn’t know why.
“If you look years down the line, a very, very large fraction of those black holes that don’t have radio emission in those early days will suddenly light up in radio waves,” said lead author Yvette Cendes. 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 anticipated.”
Although black holes cannot be observed directly, scientists can observe a TDE because these events emit light, radios and other waves for a few weeks or months as they occur.
The question is: where is it stored before being “burped”?
Scientists know for sure that it doesn’t come from inside a black hole, because objects have an event horizon where gravity is so strong that not even light can escape.
Cendes added: “We don’t really understand if the material seen in the radio waves is from the accretion disk or is stored somewhere closer to the black hole.
“But black holes are definitely clutter eaters.”
The researchers plan to continue monitoring the black holes they have observed, 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 “burp” years later, which experts hope will deepen understanding of this strange behavior.
The new research has been published in the preprint database arXiv but not yet peer reviewed.
WHAT’S INSIDE A BLACK HOLE?
Black holes are strange objects in the universe that get their name from the fact that nothing can escape their gravity, not even light.
If you venture too close and cross what is known as the event horizon, the point from which no light can escape, you will also be trapped or destroyed.
For small black holes, you would never survive such a close approach anyway.
Tidal forces near the event horizon are enough to stretch any matter until it is just a string of atoms, in a process physicists call “spaghettification.”
But for large black holes, like the supermassive objects at the heart of galaxies like the Milky Way, which weigh tens of millions or even billions of times the mass of a star, crossing the event horizon would be uneventful.
Because it should be possible to survive our world’s transition to black holes, physicists and mathematicians have long wondered what that world would look like.
They turned to Einstein’s general relativity equations to predict the world inside a black hole.
These equations work well until an observer reaches the center or the singularity, where in theoretical calculations the curvature of spacetime becomes infinite.