Astronomers un­cover ev­i­dence of meta­mor­pho­sis of gal­ax­ies

The China Post - - LIFE -

From round disks to oval clus­ters; many gal­ax­ies in the Uni­verse have un­der­gone a dra­matic trans­for­ma­tion over the past eight bil­lion years or so, re­searchers re­ported on Thurs­day.

An in­ter­na­tional team looked at data on some 10,000 of the bil­lions of gal­ax­ies in the ob­serv­able Uni­verse to­day, and then used the Hub­ble and Her­schel tele­scopes to peer back in time.

They found that 83 per­cent of stars formed since the Big Bang about 13.7 bil­lion years ago, were ini­tially grouped in flat, ro­tat­ing, disc-shaped gal­ax­ies, ac­cord­ing to a state­ment from the Cardiff Univer­sity’s School of Physics and As­tron­omy, whose astronomers led the study.

“How­ever, only 49 per­cent of stars that ex­ist in the Uni­verse to­day are lo­cated in these disc­shaped gal­ax­ies, the re­main­der are lo­cated in oval-shaped gal­ax­ies,” it said.

“The

re­sults

sug­gest a mas- sive trans­for­ma­tion in which disc­shaped gal­ax­ies be­came oval­shaped gal­ax­ies.”

The bulk of stars in the Uni­verse are thought to have been formed be­tween 12 bil­lion to eight bil­lion years ago.

The team of­fered two hy­pothe­ses — oval gal­ax­ies may be formed when two disc-shaped clus­ters move too close to one another and are merged by grav­ity into a dis­or­derly clump, or the stars in a round, flat gal­axy grad­u­ally mi­grate to­wards the cen­ter to pro­duce a dis­or­derly, roughly oval-shaped pile-up.

Such galac­tic shape-shift­ing had been the­o­rized be­fore, said lead au­thor Steve Eales. “But by com­bin­ing Her­schel and Hub­ble, we have for the first time been able to ac­cu­rately mea­sure the ex­tent.”

“Gal­ax­ies are the ba­sic build­ing blocks of the Uni­verse, so this meta­mor­pho­sis re­ally does rep­re­sent one of the most sig­nif­i­cant changes in its ap­pear­ance and prop­er­ties in the last eight bil­lion years,” he said.

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