Sci­en­tists are get­ting closer to solv­ing one of astron­omy’s big­gest mys­ter­ies

The Washington Post - - POLITICS & THE NATION - BY SARAH KA­PLAN sarah.ka­[email protected]­

Imag­ine a flash of ra­dio en­ergy so pow­er­ful it out­shines the sun. Now imag­ine a flash like this go­ing off nearly ev­ery minute all across the cos­mos.

These are fast ra­dio bursts, some of the most enig­matic phe­nom­ena in astron­omy. Sci­en­tists don’t know where they come from, or what ce­les­tial event could be so dra­matic yet com­mon enough to pro­duce thou­sands of bursts ev­ery day.

But they think they’re clos­ing in on an an­swer. At the win­ter meet­ing of the Amer­i­can As­tro­nom­i­cal So­ci­ety this week, re­searchers at a pow­er­ful new Cana­dian tele­scope an­nounced the de­tec­tion of 13 new fast ra­dio bursts (FRBs) over two months of ob­ser­va­tions; five dozen bursts were found over the past 12 years.

One of the newly de­tected bursts is a rare “re­peater.” Re­searchers saw six flashes com­ing from the same spot in the sky, which they hope will make it eas­ier to de­ter­mine the source of the sig­nal. Only one other re­peat­ing FRB has ever been de­tected.

This sud­den rush of tan­ta­liz­ing clues has de­lighted astro­physi­cists.

“These things are com­ing to us from half­way across the uni­verse, and we don’t re­ally know any­thing about them,” said McGill Univer­sity’s Shri­harsh Ten­dulkar, a lead au­thor of one of two pa­pers in the jour­nal Na­ture about the find­ings. “Isn’t that ex­cit­ing?”

Work on the Cana­dian Hy­dro­gen In­ten­sity Map­ping Ex­per­i­ment (CHIME), which Ten­dulkar and his col­leagues used for their re­search, was not quite com­plete when the ini­tial 13 FRBs were de­tected in July and Au­gust. How­ever, the in­stru­ment, which maps a three-de­gree-wide swath of the sky each night, was al­ready a dra­matic im­prove­ment over more-tra­di­tional tele­scopes, which can fo­cus only on a sin­gle spot.

CHIME has been fully op­er­a­tional since Septem­ber, and sci­en­tists on the project have hinted that at least 100 more bursts will be re­ported in the weeks to come.

“With fast ra­dio bursts, it’s al­ways felt like the more an­swers we get, the more ques­tions we have,” said Sarah Burke-Spo­laor, an as­tro­physi­cist at West Virginia Univer­sity who was not in­volved in the re­search. “But I think we’re reach­ing the peak of that moun­tain.” Shami Chat­ter­jee, an FRB re­searcher at Cor­nell Univer­sity, agreed. “This field is about to break wide open,” he said.

When the first FRB was de­tected, in 2007, many sci­en­tists thought it had to be the re­sult of some tele­scopic mix-up. The sig­nals are so brief that sci­en­tists thought they must come from some­thing in­cred­i­bly small — no big­ger than New Jersey — yet they pack as much en­ergy into a mil­lisec­ond as the sun emits all day. They are also dis­persed — high­fre­quency wave­lengths ar­rive ear­lier than lower-fre­quency ones — which sug­gests they travel long dis­tances across vast ex­panses of space to reach astronomers’ ra­dio dishes.

Sci­en­tists have scores of the­o­ries about what might cre­ate such po­tent sig­nals — spin­ning cores of col­lapsed stars, pow­er­ful mag­netic fields around black holes, the fog of dust and gas from which new stars form. But only one burst has ever been traced back to its source: A re­peat­ing burst called FRB 121102 flick­ers pe­ri­od­i­cally from a dim dwarf gal­axy 3 bil­lion light-years away.

The re­peater de­tected by CHIME bears a strong re­sem­blance to FRB 121102, said Univer­sity of Toronto as­tro­physi­cist Cherry Ng, lead au­thor of the sec­ond Na­ture pa­per. Both have what Ng calls “struc­ture” — dis­tinc­tive pat­terns in the tim­ing and fre­quency of the sig­nals.

“It’s re­ally tempt­ing . . . to think that this is maybe a defin­ing fea­ture,” Ng said. “But we have to be care­ful. We still have a sam­ple size of only two.”

The CHIME re­searchers are work­ing with an­ten­nas in cen­tral New Mex­ico to pin down the gal­axy to which the sec­ond re­peater be­longs. The fact that it re­peats gives them a good chance of spot­ting it again. They hope that trac­ing the ra­dio sig­nal of a known vis­i­ble ob­ject may re­veal what pro­duced it.

But that is just one of the riddles as­so­ci­ated with this “fan­tas­tic phe­nom­e­non,” said Ten­dulkar. Sci­en­tists are still de­bat­ing whether re­peat­ing FRBs come from the same source as the one­time flashes or, in­stead, are a dis­tinct type of event. They do not know whether the bursts are like flash­bulbs, light­ing up the sky in ev­ery di­rec­tion, or fo­cused beams, which would re­quire less en­ergy but must be more fre­quent for Earth to see so many of them.

It is pos­si­ble, he said, that there are sev­eral types of FRBs, each cre­ated by a dif­fer­ent ce­les­tial cat­a­clysm.

The mys­tery of fast ra­dio bursts has al­ways been a large part of their ap­peal, Ng said. “I think we are just drawn to any­thing un­known.”

She is just as thrilled by the rev­e­la­tions that will emerge from solv­ing this mys­tery. FRBs are among the few types of sig­nal that in­ter­act with the dif­fuse fog of elec­trons ex­ist­ing among gal­ax­ies. If sci­en­tists can fig­ure out how FRBs ought to look when they leave their sources, they may be able to probe the in­ter­ga­lac­tic medium by study­ing the way the sig­nals change.

“We are very far from that yet,” Ng said. How­ever, she said the prom­ise is what keeps her work­ing. “It could be a start to a whole new field in astron­omy.”


The tele­scope ar­ray used in the Cana­dian Hy­dro­gen In­ten­sity Map­ping Ex­per­i­ment, or CHIME, to study the phe­nom­e­non of fast ra­dio bursts. “These things are com­ing to us from half­way across the uni­verse,” said McGill Univer­sity’s Shri­harsh Ten­dulkar, an as­tro­physi­cist

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