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Record-breaking Galaxy Five Billion Light-Years Away Shows We Live in a Magnetic Universe

August 28, 2017

Toron­to, ON – A team of astronomers has observed the mag­net­ic field of a galaxy five bil­lion light-years from Earth. The galaxy is the most dis­tant in which a coher­ent mag­net­ic field has been observed and pro­vides impor­tant insight into how mag­net­ism in the Uni­verse formed and evolved.

The obser­va­tion shows a mag­net­ic field of a sim­i­lar strength and con­fig­u­ra­tion to that seen in our own Milky Way Galaxy, even though the dis­tant galaxy is five bil­lion years younger than ours. This is evi­dence that galac­tic mag­net­ic fields form ear­ly in a galaxy’s life and remain rel­a­tive­ly sta­ble.

“This find­ing is excit­ing,” says Dr. Sui Ann Mao, an astronomer and Min­er­va Research Group leader at the Max Planck Insti­tute for Radio Astron­o­my and lead author of the paper describ­ing the obser­va­tion. “It is now the record hold­er of the most dis­tant galaxy for which we have this mag­net­ic field infor­ma­tion.” The paper will be pub­lished August 28th in Nature Astron­o­my.

Galax­ies have their own mag­net­ic fields, but they are incred­i­bly weak—a mil­lion times weak­er than the Earth’s mag­net­ic field. One the­o­ry sug­gests that the mag­net­ic field of a young galaxy starts off weak and tan­gled, becom­ing stronger and more orga­nized over time.

But, because the mag­net­ic field of the observed galaxy is not much dif­fer­ent from the fields we observe in our own Milky Way Galaxy and near­by galax­ies, the detec­tion is evi­dence that galac­tic mag­net­ism appears rel­a­tive­ly ear­ly, rather than grow­ing slow­ly over time.

“This means that mag­net­ism is gen­er­at­ed very ear­ly in a galaxy’s life by nat­ur­al process­es, and thus that almost every heav­en­ly body is mag­net­ic,” says Prof. Bryan Gaensler, Dun­lap Insti­tute for Astron­o­my & Astro­physics, Uni­ver­si­ty of Toron­to, and a co-author of the paper. “The impli­ca­tion is that we need to under­stand mag­net­ism to under­stand the Uni­verse.”

Study­ing the evo­lu­tion of galac­tic mag­net­ic fields requires obser­va­tions of galax­ies at dif­fer­ent dis­tances from us because such obser­va­tions show us galax­ies at dif­fer­ent ages.

But these obser­va­tions are dif­fi­cult to make, in part because a mag­net­ic field can’t be detect­ed direct­ly. Instead, we can only detect one by observ­ing the mag­net­ic fin­ger­print it leaves on light pass­ing through it—an effect referred to as Fara­day Rota­tion.

Mao, Gaensler and their col­leagues were able to make their obser­va­tion because a quasar—a very bright and dis­tant galaxy—lies beyond the galaxy being stud­ied, along the same line of sight. Thanks to this chance align­ment, the quasar’s light pass­es through the galaxy’s mag­net­ic field on its way to us, pick­ing up the tell-tale Fara­day Rota­tion fin­ger­print.

The obser­va­tion was made using the Karl G. Jan­sky Very Large Array, an array of radio tele­scope dish­es in Plains of San Agustin in the New Mex­i­co desert, oper­at­ed by the Nation­al Radio Astron­o­my Obser­va­to­ry.

“Nobody knows where cos­mic mag­net­ism comes from or how it was gen­er­at­ed,” says Gaensler. “But now, we have obtained a major clue need­ed for solv­ing this mys­tery, by extract­ing the fos­sil record of mag­net­ism in a galaxy bil­lions of years before the present day.”

Addi­tion­al notes:

1) Fara­day Rota­tion: A radio wave, like a wave on a pond, oscil­lates or vibrates in a sin­gle direc­tion or plane; for exam­ple, a wave on the sur­face of a pond move up and down in a ver­ti­cal plane. When a radio sig­nal pass­es through a mag­net­ic field, the mag­net­ic field rotates the plane of vibra­tion. This so-called Fara­day Rota­tion gives us infor­ma­tion about the strength and the polarity—or direction—of the mag­net­ic field.

2) In the Hub­ble Space Tele­scope image, there appear to be three objects. Of the three, the cen­tral, dim­mer object is the galaxy. Both of the two remain­ing objects are lensed images of the same, more dis­tant quasar. As light from the quasar trav­els toward us, its path is bent by the grav­i­ty of the galaxy, just as the tra­jec­to­ry of a space­craft is bent as it flies by a plan­et. We see light from the quasar that trav­eled along dif­fer­ent paths as mul­ti­ple images of the same object. Says Mao, “Hav­ing mul­ti­ple lensed images of the back­ground quasar to probe along dif­fer­ent sight lines through the lens­ing galaxy is the key to get­ting the mea­sure­ment we have here.”

The Dun­lap Insti­tute for Astron­o­my & Astro­physics at the Uni­ver­si­ty of Toron­to is an endowed research insti­tute with over 70 fac­ul­ty, post­docs, stu­dents and staff, ded­i­cat­ed to inno­v­a­tive tech­nol­o­gy, ground-break­ing research, world-class train­ing, and pub­lic engage­ment. The research themes of its fac­ul­ty and Dun­lap Fel­lows span the Uni­verse and include: opti­cal, infrared and radio instru­men­ta­tion; Dark Ener­gy; large-scale struc­ture; the Cos­mic Microwave Back­ground; the inter­stel­lar medi­um; galaxy evo­lu­tion; cos­mic mag­net­ism; and time-domain sci­ence.

The Dun­lap Insti­tute, Depart­ment of Astron­o­my & Astro­physics, Cana­di­an Insti­tute for The­o­ret­i­cal Astro­physics, and Cen­tre for Plan­e­tary Sci­ences com­prise the lead­ing cen­tre for astro­nom­i­cal research in Cana­da, at the lead­ing research uni­ver­si­ty in the coun­try, the Uni­ver­si­ty of Toron­to.

The Dun­lap Insti­tute is com­mit­ted to mak­ing its sci­ence, train­ing and pub­lic out­reach activ­i­ties pro­duc­tive and enjoy­able for every­one, regard­less of gen­der, sex­u­al ori­en­ta­tion, dis­abil­i­ty, phys­i­cal appear­ance, body size, race, nation­al­i­ty or reli­gion.


For more infor­ma­tion:

Prof. Bryan Gaensler, Direc­tor
Dun­lap Insti­tute for Astron­o­my & Astro­physics
Uni­ver­si­ty of Toron­to
c: 416–522-0887

Chris Sasa­ki
Com­mu­ni­ca­tions Coor­di­na­tor | Press Offi­cer
Dun­lap Insti­tute for Astron­o­my & Astro­physics
Uni­ver­si­ty of Toron­to
p: 416–978-6613