The kilo­nova story

A pair of neu­tron stars that merged over a bil­lion light years away could have cre­ated an un­ex­pected cos­mic rel­a­tive of a past grav­i­ta­tional wave

All About Space - - Contents - Re­ported by Lee Cavendish

Two neu­tron stars col­lided and we weren't ex­pect­ing the re­sult

The uni­verse is full of enor­mous cos­mic events that pro­duce vast amounts of en­ergy and el­e­ments that are spread through­out the cos­mos. Some of these take mil­lions of years, for ex­am­ple ob­serv­ing a star slowly de­plete its fuel be­fore ex­plod­ing, re­sult­ing in a su­per­nova. On the other hand, some take place in a frac­tion of a sec­ond, like the merg­ing of neu­tron stars that cre­ates grav­i­ta­tional waves. The lat­ter are an enigma to as­tronomers, and our un­der­stand­ing of them has only evolved sig­nif­i­cantly in the last year or so with the Laser In­ter­fer­om­e­ter Grav­i­ta­tional-Wave Observatory, or LIGO as it’s more com­monly known, in the United States and the Virgo in­ter­fer­om­e­ter in Italy.

Just re­cently, as­tronomers found a pe­cu­liar sig­nal that they be­lieve to be from two col­lid­ing neu­tron stars. This event was orig­i­nally spot­ted as a rapid emis­sion of light in the gamma-ray sec­tion of the elec­tro­mag­netic spectrum, giv­ing it the name GRB – an ab­bre­vi­a­tion for gamma-ray burst – 150101B. This rapid burst of light was first spot­ted by the Gamma-ray Burst Mon­i­tor aboard NASA’s Fermi Space Tele­scope on 1 Jan­uary 2015. Fol­lowup ob­ser­va­tions were made us­ing a whole host of tele­scopes over a se­ries of wave­lengths, in­clud­ing NASA’s Neil Gehrels Swift Observatory and Chan­dra X-ray Observatory, both in space, and the 6.5-me­tre (21-foot) Mag­el­lan Tele­scope at the Las Cam­panas Observatory in Chile.

“GRB150101B was dis­cov­ered by NASA's Fermi mis­sion, but its po­si­tion in the sky was not known very well and we could not per­form any other ob­ser­va­tions be­cause we did not know where to look,” Dr Eleonora Troja from NASA’s God­dard Space Flight Cen­ter in Green­belt, Mary­land, United

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