Pole scientists trace rays to a galaxy far, far away

HIGH energy cosmic rays rain down on Earth every day – but until now scientists had no idea where they come from.

Now the discovery of a single subatomic particle provides evidence for their source, a galaxy four billion light years away.

The particle, called a neutrino, was detected on September 22 last year by the IceCube observatory, a remote facility sunk a mile beneath the South Pole.

A grid of over 5,000 super-sensitive sensors picked up the neutrino as it moved through the ice.

Its source can be tracked because neutrinos travel in straight lines, passing through planets and stars.

As a result, astronomers were able to follow its journey back to a ‘blazar’, a class of galaxy containing a supermassive black hole four billion light years away near the constellation Orion.

A key feature of blazars are its twin jets of light and particles that shoot from the poles of the swirling whirlwind of mate-

rial surrounding the black hole.

The neutrino detected by IceCube is thought to have been created by highenergy cosmic rays from the jets interacting with nearby material, the journal Science reports.

The blazar believed to have generated the neutrino, named TXS 0506 + 056, was located in less than a minute after the IceCube team shared co-ordinates for follow-up observations with astronomers worldwide.

Professor Paul O’Brien, a member of the international team of astronomers from the University of Leicester, said: ‘Neutrinos rarely interact with matter.

‘To detect them at all from the cosmos is amazing, but to have a possible source identified is a triumph. This result will allow us to study the most distant, powerful energy sources in the universe in a completely new way.’

Being able to detect high energy neutrinos provides another window on the universe, said scientists. The others are electromagnetic radiation, recently discovered gravitational waves, and now neutrinos.

Finding source is a triumph