Scientists have identified a mysterious barrier in space that prevents high-energy cosmic rays from reaching the supermassive black hole at the centre of our galaxy.
After creating a map of radiation at the core of the Milky Way, the team of researchers from the Chinese Academy of Sciences in Nanjing found that an unexplained force appears to be accelerating any cosmic particles that approach the galaxy’s centre to incredible speeds.
The team reported their findings in the November 9 issue of scientific journal Nature Communications.
They described the unknown force as an invisible "barrier" that surrounds the entire core fo the galaxy, keeping the density of cosmic rays there far lower than the expected level.
At this stage they say, it’s not clear what might be creating this massive wall in space.
The centre of our galaxy, and quite possibly all galaxies, contains a gigantic black hole with a mass estimated at around four million times that of our Sun.
It lies in the direction of the constellation Sagittarius, roughly 26,000 light-years from us.
Massive wall of galaxies 'not so distant' from the Earth discovered by astronomers
It was first identified in August 1931 as a super-powerful radio source and while it’s very hard to directly observe black holes, several super-powerful flares have been imaged coming from the object known as Sagittarius A* as it gobbles up large asteroids and other objects that stray too close to its event horizon.
Using data from the Fermi Large Area Telescope, the researchers have identified Sagittarius A* as a massively powerful cosmic ray source, shooting the energetic particles across our galaxy.
But their map also revealed a mysterious "barrier" surrounding the galactic centre, where the density of cosmic rays drops off dramatically.
As yet, what’s creating this wall in space remains unknown and has baffled scientists.
The researchers speculate that it could have been created by dense clouds of dust and other cosmic debris collapsing in on themselves, compressing the magnetic fields there and creating a cosmic-ray barrier.
Another potential explanation is that streams of charged particles released from the tightly-packed stars at the galactic centre could be “pushing back” at the tide of cosmic radiation, like a hugely-magnified version of the “solar wind” that pervades our solar system.
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