By Will Dunham
WASHINGTON, Feb 5 (Reuters) – Scientists are observing the behavior of a supermassive black hole that is displaying exceptionally messy eating habits.
Primarily using radio telescopes in New Mexico and South Africa, they are watching the black hole, residing at the center of a galaxy far beyond our Milky Way, as it continues to belch out a fast-moving jet of material after ripping apart and eating a star that made the mistake of wandering too close.
What makes this stellar fatal encounter unusual is the intensity and duration of the black hole’s post-meal indigestion.
Material left over from the star did not begin shooting into space until two years after it was shredded into its component gases by the black hole’s gravitational forces. But this jet now has been shooting into space for six years – longer than has ever been observed before – and continues to intensify in what has become one of the most powerful single events ever detected in the universe.
“The exponential rise in the luminosity of this source is unprecedented. It’s now about 50 times brighter than when it was first discovered, and is now incredibly bright for an object in radio waves. This has been going on for years now, and no sign of stopping. That is super unusual,” said University of Oregon astrophysicist Yvette Cendes, lead author of the study published on Thursday in the Astrophysical Journal.
Black holes are exceptionally dense objects with gravity so strong not even light can escape. This black hole is located about 665 million light years from Earth. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
The black hole is about 5 million times more massive than the sun. That makes it roughly comparable to the supermassive black hole at the center of our own galaxy, which has a mass about 4 million times greater than the sun.
The doomed star was a type called a red dwarf that was about a tenth as massive as the sun.
An event horizon is the point of no return for material drawn by a black hole’s gravitational strength. When a star is pulled apart by a black hole, it is called a tidal disruption event because it results from the same gravitational dynamics responsible for ocean tides on Earth.
“Any object that approaches too close to the event horizon of a black hole risks being torn apart by tidal forces and stretched into a long stream of debris, a process called ‘spaghettification,'” University of Arizona astrophysicist and study co-author Kate Alexander said.
“After the star was torn apart, some of this gas fell towards the black hole and heated up, and the black hole began to consume the star. The bright radio light that we see with our telescopes is produced by star stuff that got close to but never actually crossed the event horizon – like a picky baby chewing her food and violently spitting it back out, rather than swallowing it,” Alexander said.
The researchers are not exactly sure why this tidal disruption event with its jet, formally called a relativistic jet, has been so spectacular.
“As for what causes the relativistic jet in the first place – we don’t actually know, and it’s an active area of research. Likely it has something to do with magnetic fields around the black hole, but also clearly has to be something unusual or else we’d see more of them,” Cendes said.
The question now is how long this jet will continue to intensify. The researchers suspect it may peak later this year or next year.
“After the emission peaks, it should fade slowly, so we will probably still be able to see it for a decade or more,” Alexander said.
(Reporting by Will Dunham, Editing by Rosalba O’Brien)
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