Neu­trino burst solves mys­tery of COS­MIC RAY ORI­GINS

Ghostly par­ti­cles of­fer a key to the ori­gins of high-en­ergy rays

Sky at Night Magazine - - BULLETIN -

Astronomer­s are a step closer to solv­ing the cen­tury-old co­nun­drum of where cos­mic rays come from, hav­ing lo­cated the source of a burst of neu­tri­nos, the ghostly sub-atomic par­ti­cles cre­ated at the same time as the rays.

The neu­trino burst was de­tected on 22 Septem­ber 2017 by the Ice­Cube tele­scope in Antarc­tica, and astronomer­s cal­cu­lated its rough lo­ca­tion in the sky. Af­ter a year of follow-up ob­ser­va­tions, they have pin­pointed its ori­gin to a blazar – a gal­axy with a rapidly spin­ning black hole that fires out jets of par­ti­cles. This par­tic­u­lar blazar flared up in vis­i­ble light around the same time the neu­tri­nos were emit­ted.

This is only the sec­ond time that neu­tri­nos have been de­tected out­side the So­lar Sys­tem and the first time they have been traced back to the cen­tre of an­other gal­axy.

“Neu­tri­nos rarely in­ter­act with mat­ter,” says Paul O’Brien, head of Physics and As­tron­omy at the Uni­ver­sity of Le­ices­ter and a mem­ber of the ob­serv­ing team. “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.”

Dis­cov­ered in 1910, cos­mic rays are par­ti­cles with enough en­ergy to travel be­tween galax­ies. Un­for­tu­nately, dis­cov­er­ing what cre­ates such en­er­getic par­ti­cles has been dif­fi­cult as the rays’ flight is de­flected by the mag­netic fields they meet along the way. This means the di­rec­tion in which they ar­rive at Earth doesn’t nec­es­sar­ily point back to where they were cre­ated.

But cos­mic rays are not born alone: when they are cre­ated, neu­tri­nos form along­side them. As neu­tri­nos have no charge, they are un­af­fected by mag­netic fields and so astronomer­s can follow their path to dis­cover where they came from.

“This event – the first time we’ve been able to as­so­ciate light with the source of a high-en­ergy neu­trino – oc­curred less than five weeks af­ter the first joint de­tec­tion of light and grav­i­ta­tional waves,” says Phil Evans, the de­vel­op­ment sci­en­tist for Swift, a tele­scope that fol­lowed up the de­tec­tion. “We truly are en­ter­ing the era of multi-mes­sen­ger as­tron­omy.”

The Ice­Cube tele­scope in Antarc­tica has found a clue to the ori­gins of cos­mic rays

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.