Black holes have weaker magnetic fields than thought: study

Black holes - known for their intense gravitational pull capable of gobbling up entire stars - may have significantly weaker magnetic fields than previously thought, a study has found.

A 64-kilometre-wide black hole 8,000 light years from Earth named V404 Cygni has yielded the first precise measurements of the magnetic field that surrounds the deepest wells of gravity in the universe.

Researchers from University of Florida (UF) in the US found the magnetic energy around the black hole is about 400 times lower than previous crude estimates.

The measurements bring scientists closer to understanding how black holes' magnetism works, deepening our knowledge of how matter behaves under the most extreme conditions - knowledge that could broaden the limits of nuclear fusion power and GPS systems.

The findings, published in the journal Science, will help scientists solve the half-century-old mystery of how "jets" of particles travelling at nearly the speed of light shoot out of black holes' magnetic fields, while everything else is sucked into their abysses.

"Our surprisingly low measurements will force new constraints on theoretical models that previously focused on strong magnetic fields accelerating and directing the jet flows. We weren't expecting this, so it changes much of what we thought we knew," said Stephen Eikenberry, a  professor at UF.

Researchers developed the measurements from data collected in 2015 during a black hole's rare outburst of jets.

The event was observed through the lens mirror of the 34 -foot Gran Telescopio Canarias, the world's largest telescope, located in Spain.

Smaller jet-producing black holes, like the one observed for the study, are the rock stars of galaxies. Their outbursts occur suddenly and are short-lived, according to Yigit Dalilar and Alan Garner, doctoral students at UF.

The 2015 outbursts of V404 Cygni lasted only a couple of weeks. The previous time the same black hole had a similar episode was in 1989.

"To observe it was something that happens once or twice in one's career," Dalilar said.

"This discovery puts us one step closer to understanding how the universe works," he said.