Why do black hole flares die out? It may be down to how stars spin

Some stars encounter supermassive black holes and live to tell the tale.

New research shows why the flares these encounters cause dim over repeated episodes, and it may be down to the way these stars spin and an escaping binary partner that leaves them to be a stellar snack for a black hole.

Some stars are unfortunate enough to encounter the supermassive black holes that sit at the heart of every galaxy, being subjected to immense tidal forces that turn them into a strand of stellar spaghetti, a process called " spaghettification ." This plasma pasta wraps around the black hole and is gradually fed to it, with some former star stuff being ejected as near-light-speed jets.

These occurrences are called tidal disruption events (TDEs).

However, other stars get a reprieve, passing close enough to a supermassive black hole for the cosmic titan to take a bite and strip off material, but not close enough to be fully destroyed.

As the star orbits the supermassive black hole, it takes repeated "bites," with this stellar snacking called a repeating partial tidal disruption event (rpTDE).

Each incident causes a flare of light from the vicinity of the black hole , as would be expected from the brightening seen during a standard TDE.

But a strange pattern has emerged in rpTDES; each successive flare can become dimmer.

Scientists have struggled to explain this dimming for some time, but finally a team of researchers from Syracuse University may have solved this puzzle.

To reach an answer to black hole flare dimming, the team considered a factor that hadn't been thought of before: the spin of the star itself.

This element explained the dimming of black hole flaring and also helped to explain why not all rpTDEs play out the same.

"We were puzzled by this for two years," team leader Ananya Bandopadhyay of Syracuse University said in a statement.

A new spin on stellar snacking Bandopadhyay and colleagues previously determined that how much material a star loses during repeated rpTDE episodes depends partially on its internal structure, which in turn depends on its mass.

Bandopadhyay compares a low-mass star to a fluffy meringue, which makes it more susceptible to the tidal forces generated by the black hole, allowing more material to be stripped from deeper within the star.