Source : phys
The popular conception goes that nothing can run away or escape from black hole. Once something passes the event horizon – the so-called point of no return – it stays there, forever, bound by a gravitational field’ not even light can escape.
But a rotating black hole generates large amounts of energy, which, theoretically, are often extracted from the ergosphere, a area that sits just on the surface of the event horizon. This has been shown both theoretically and experimentally – and now a team of astrophysicists has found what they believe is observational evidence for it.
The smoking gun is that the most powerful gamma-ray burst we’ve ever detected, GRB 190114C, a colossal flare clocking in at around a trillion electron volts (1 TeV), from 4.5 billion light-years away.
“Gamma-ray bursts, the foremost powerful transient objects within the sky, release energies of up to a couple of 10^54 erg in only a couple of seconds,” said astrophysicist Remo Ruffini of the International Center for Relativistic Astrophysics Network (ICRANet) headquartered in Italy.
“Their luminosity within the gamma-rays, within the interval of the event, is as large because the luminosity of all the stars of the observable Universe! Gamma-ray bursts are thought to be powered, by an up-to-now unknown mechanism, by stellar-mass black holes.”
Last year, Ruffini and his colleagues came up with an answer for this mechanism – a process they need called a binary-driven hypernova.
It starts with close binary numeration system consisting of a carbon-oxygen star at end of its life, and a neutron star . When the carbon-oxygen star goes supernova, material ejected are often rapidly slurped up by the companion neutron star . Thus, that companion passes the critical mass point and collapses into black-hole, which launches a burst of gamma rays, also as jets of material from its poles at nearly light-speed.
(The core of the carbon-oxygen star collapses into a second star , leading to a black hole-neutron star binary.)
Now, in new paper, Ruffini and his colleagues led by ICRANet’s Rahim Moradi have described the mechanism which will launch such a high-energy gamma-ray burst: the acceleration of particles along magnetic flux lines inherited from the black hole’s parent neutron-star . That magnetic flux extracts rotational energy from the black hole’s ergosphere.
“The novel engine presented in new publication,” Ruffini explained, “makes the work through a purely general relativistic, gravito-electrodynamical process: a rotating black hole region , interacting with a surrounding magnetic flux , creates an electrical field that accelerates ambient electrons to ultrahigh-energies resulting in high-energy radiation and ultrahigh-energy cosmic rays.”
Relativistic, or near light-speed, jets aren’t uncommon in active galactic nuclei, the supermassive black hole region monsters at the cores of galaxies. These jets are thought to make from the accretion process, which goes as follows.
A huge disk of material swirls round the active black hole region , falling into it from the inner edge, but not all of this material falls onto black hole. a number of it, astronomers believe, is funneled and accelerated along magnetic flux lines round the outside of the black-hole to the poles, where it’s launched in to space within the form of collimated jets.
We know black holes and neutron stars can have powerful magnetic fields, and therefore the evidence suggests these can act as a synchrotron (a sort of particle accelerator). Evidence also suggests that a magnetic flux synchrotron plays a task in launching a gamma-ray burst during the formation of a region .
Studying GRB 190114C, Moradi and his team have found an identical mechanism – but, instead of endless emission process, it’s discrete, repeating over and over, releasing whenever a quantum of black-hole energy to produce the observed gamma-ray emission following the gamma-ray burst.
Based on observations of GRB 190114C, the team was ready to reconstruct the sequence of events.
The carbon-oxygen star goes supernova, while the core collapses into a neutron-star ; a number of that ejected material falls back onto the newly formed neutron star, producing an X-ray glow – as observed by the Swift telescope.
Some of the material also falls onto neutron star companion, pushing it over the mass limit to create a black-hole – this process would are smooth, taking just 1.99 seconds. Then material continues to fall onto the newly formed black-hole, producing a gamma-ray burst from 1.99-3.99 seconds.
Finally, more material falling onto black-hole leads to the formation of jets, and gamma ray within the gigaelectronvolt range, from the extraction of rotational energy.
Other scientists may not agree with the findings; a team last year found that the gamma-ray burst was the results of a collapsing magnetic flux , as an example . it’s going to not even apply to all or any gamma-ray bursts. Nevertheless, all the parts seem to suit the observations of GRB 190114C very neatly.
“The proof that we might use the extractable rotational energy of a black hole region to define the high-energy jetted emissions of gamma-ray bursts and active galactic nuclei stands alone,” Ruffini said.
“A long march of successive theoretical progress and new physics discovered using observations of GRBs has delivered to this result which has been [awaited] for about 50 years of relativistic astrophysics.”
The research has been published in Astronomy & Astrophysics.
