Back­ground space hum may re­veal hid­den black holes

Financial Chronicle - - MISCELLANY -

Sci­en­tists have de­vel­oped a new tech­nol­ogy that can lis­ten to back­ground hum­ming of deep space and un­veil thou­sands of hid­den black hole col­li­sions missed by grav­i­ta­tional-wave de­tec­tors. Deep space is not as silent as we have been led to be­lieve. Ev­ery few min­utes a pair of black holes smash into each other. These cat­a­clysms re­lease rip­ples in the fab­ric of space­time known as grav­i­ta­tional waves.

The grav­i­ta­tional waves from black hole merg­ers im­print a dis­tinc­tive whoop­ing sound in the data col­lected by grav­i­ta­tional-wave de­tec­tors. The new tech­nique de­vel­oped by re­searchers from Monash Univer­sity in Aus­tralia is ex­pected to re­veal the pres­ence of thou­sands of pre­vi­ously hid­den black holes by teas­ing out their faint whoops from a sea of static.

Last year, in one of the big­gest astro­nom­i­cal dis­cov­er­ies of the 21st cen­tury, LIGO Sci­en­tific Col­lab­o­ra­tion (LSC) and Virgo Col­lab­o­ra­tion re­searchers mea­sured grav­i­ta­tional waves from a pair of merg­ing neu­tron stars.

The first grav­i­ta­tional-wave was dis­cov­ered in 2015, when rip­ples in the fab­ric of space time gen­er­ated by the col­li­sion of two black holes in the dis­tant uni­verse were wit­nessed, con­firm­ing Al­bert Ein­stein's 1915 gen­eral the­ory of rel­a­tiv­ity.

To date, there have been six con­firmed, or gold plated, grav­i­ta­tional-wave events an­nounced by the LIGO and Virgo Col­lab­o­ra­tions. How­ever there are more than 100,000 grav­i­ta­tional wave events ev­ery year too faint for LIGO and Virgo to un­am­bigu­ously de­tect, ac­cord­ing to Eric Thrane from the ARC Cen­tre of Ex­cel­lence for Grav­i­ta­tional

The grav­i­ta­tional waves from these merg­ers com­bine to cre­ate a grav­i­ta­tional-wave back­ground. While the in­di­vid­ual events that con­trib­ute to it can­not be re­solved in­di­vid­u­ally, re­searchers have sought for years to de­tect this quiet grav­i­ta­tional-wave hum.

Re­searchers have de­vel­oped a new, more sen­si­tive way of search­ing for the grav­i­ta­tional-wave back­ground. "Mea­sur­ing the grav­i­ta­tional-wave back­ground will al­low us to study pop­u­la­tions of black holes at vast dis­tances. Some­day, the tech­nique may en­able us to see grav­i­ta­tional waves from the Big Bang, hid­den be­hind grav­i­ta­tional waves from black holes and neu­tron stars," Thrane said.

The re­searchers de­vel­oped com­puter sim­u­la­tions of faint black hole sig­nals, col­lect­ing masses of data un­til they were con­vinced that - within the sim­u­lated data - was faint, but un­am­bigu­ous ev­i­dence of black hole merg­ers.

Re­searchers are op­ti­mistic that the method will yield a de­tec­tion when ap­plied to real data.

Re­cent im­prove­ments in data anal­y­sis will en­able the de­tec­tion of what peo­ple had spent decades look­ing for, they said.

The new method is es­ti­mated to be one thou­sand times more sen­si­tive, which should bring the long-sought goal within reach.

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