Black holes eat stars like messy toddlers

We’ve all seen the tremendous mess babies and toddlers make when they’re eating.

Well, imagine that on a cosmic scale and scientists say you’ll have some indication as to what it looks like when certain types of black holes devour wayward stars.

In essence, it involves taking a few bites and then flinging the remains across the universe.

Researchers at Northwestern University in Illinois made their discovery after creating 3D computer simulations of what would happen if stars the size of our sun were tossed within reach of so-called intermediate-mass black holes.

The results weren’t pretty.

Much like prey getting caught in a spider’s web, the amuse-bouche to what becomes a lengthy and violent meal is the star first getting drawn into a black hole’s orbit.

Then, every time the stellar visitor makes a single lap of its new neighbour the black hole takes a bite. 

Further cannibalising ensues with each subsequent circle until nothing is left but the star’s misshapen and incredibly dense core, the researchers said.

Done with its meal, the black hole would then theoretically eject the scant remains across the galaxy it sits in.

Not only do these new simulations offer fresh insights into the behaviours of intermediate-mass black holes, they could also provide astronomers with the clues needed to finally pinpoint where exactly these hidden giants sit in the universe. 

While astrophysicists have proven the existence of lower and higher-mass black holes, intermediate-mass ones have remained elusive and theoretical. 

‘We obviously cannot observe black holes directly because they don’t emit light,’ said Northwestern’s Fulya Kıroğlu, who led the study. 

‘So, instead, we have to look at the interactions between black holes and their environments. 

‘We found that stars undergo multiple passages before being ejected. After each passage, they lose more mass, causing a flair of light as its ripped apart. 

‘Each flare is brighter than the last, creating a signature that might help astronomers find them.’ 

Look out! Much like prey getting caught in a spider’s web, the amuse-bouche to what becomes a lengthy and violent meal is the star first getting drawn into a black hole’s orbit (depicted)

The three types of black hole are stellar ones, those that are intermediate-mass and supermassive variations.

The former are about three to 10 times the mass of our sun and are created when supernovae collapse. 

On the other end of the spectrum, supermassive black holes are millions to billions times the mass of our sun and lurk at the heart of galaxies. 

If they do exist as thought, intermediate-mass black holes would be somewhere in the middle — 10 to 10,000 times more massive than stellar remnant black holes but not nearly as big as supermassive black holes.

However, experts are yet to find indisputable observational evidence to show that they do. 

‘Their presence is still debated,’ Kıroğlu said. ‘Astrophysicists have uncovered evidence that they exist, but that evidence can often be explained by other mechanisms. 

Mysterious: The three types of black hole are stellar ones, those that are intermediate-mass and supermassive variations (stock image)

‘For example, what appears to be an intermediate-mass black hole might actually be the accumulation of stellar-mass black holes.’

To explore how these mysterious objects might behave, Kıroğlu and her team developed a series of new simulations.

This enabled them to discover that stars could orbit an intermediate-mass black hole as many as five times before finally being ejected.  

The process, the researchers claim, would create a stunning light show that should help astronomers recognise – and prove the existence of – intermediate-mass black holes.

‘It’s amazing that the star isn’t fully ripped apart,’ Kıroğlu said. 

‘Some stars might get lucky and survive the event. The ejection speed is so high that these stars could be identified as hyper-velocity stars, which have been observed at the centres of galaxies.’

Kıroğlu next plans to simulate what would happen if various types of stars – including binary and giant stellar masses – come into contact with black holes. 

The new study has been accepted for publication in The Astrophysical Journal.