Black holes are well known to be the bringers of particle doom, the dust devils of space and all-round behemoths of destruction. They account for some of the largest and most mysterious objects in the known Universe, yet we understand very little about them.
The common preconception of a black hole is that nothing can escape, not even particles of light. As every single atom, every single planet and galaxy become trapped within it’s unbreakable grip of galactic proportions, all is lost!
This isn’t entirely true.
Black holes actually spew out enormous jets of hot gas back into space, sometimes millions of light years across, these are known as plasma jets. An aspect of physics astronomers have been trying to unravel for years.
Scientists at NASA, working with the NuSTAR telescope and ULTRACAM, have made some discoveries as to how this takes place, trying to understand why these unforgiving beasts show mercy on a few lucky particles.
They are specifically interested in how some particles come to actually emit light, and here’s what they’ve found whilst observing two systems in our own Milky Way called “X-ray binaries”, each consisting of a black hole feeding from a normal star.
The study concluded that during the time it takes for a particle to be shot out of a black hole, and the time it takes to “turn-on” or emit light, there is an “acceleration zone”.
One system, called V040 Cygni, reached peak brightness in June 2015 whilst the other system, GX 339-4, reached less than one percent of its maximum expected brightness.
Despite this, both systems showed similar time delays within the acceleration zone, about one tenth of a second.
"One possibility is that the physics of the jet is not determined by the size of the disc, but instead by the speed, temperature and other properties of particles at the jet's base," said Poshak Gandhi, lead author of the study at the University of Southampton, United Kingdom
The most promising theory suggests a strong magnetic field propels some material close to the black hole at very high speeds along the plasma jets. This results in particles colliding near light-speed, energizing the plasma until it begins to emit the stream of optical radiation.
"Astronomers hope to refine models for jet powering mechanisms using the results of this study," said Daniel Stern, study co-author and astronomer based at NASA's Jet Propulsion Laboratory.
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