The Strange Life of Mag­ne­tars

iD magazine - - Con­tents -

Dead stars find new life as cos­mic pow­er­houses

They’re tiny, yet they are the true pow­er­houses of the uni­verse: Mag­ne­tars are the rem­nants of stel­lar explosions, and they con­tain an unimag­in­able amount of power. That’s why many re­searchers no longer re­gard mag­ne­tars as merely fas­ci­nat­ing, but also a po­ten­tial men­ace to mankind…


When the mag­netic field of a mag­ne­tar col­lapses, an earth­quake-like dis­charge of en­ergy is the re­sult. This gives rise to gamma-ray bursts, which could be dan­ger­ous to the Earth.

For life on the Earth, it was an apoc­a­lypse: 65 mil­lion years ago a me­teor the size of a truck crashed into Mexico. In one stroke, around 70% of the life on our planet was wiped out. It lead to the end of the di­nosaurs, and for evo­lu­tion it was a ter­ri­ble case of déjà vu. That’s be­cause the dis­as­ter was the fifth ma­jor mass ex­tinc­tion to hap­pen within 500 mil­lion years. Pre­vi­ously many sci­en­tists thought there was one main trig­ger of such epochal events in Earth’s his­tory: me­te­orite im­pacts. Now, how­ever, they’ve en­coun­tered a phe­nom­e­non that could eclipse even the largest me­te­orite: mag­ne­tars—dis­fig­ured star corpses lurk­ing in the depths of space that could strike at any time…


A star dies when it has run out of nu­clear fuel, af­ter which it breaks up un­der its own grav­ity. The re­sult is a su­per­nova—the biggest ex­plo­sion in the uni­verse, which re­leases more en­ergy than our Sun can pro­duce in 10 bil­lion years. This process gives rise to a neu­tron star—an in­cred­i­bly com­pressed piece of mat­ter with a di­am­e­ter of no more than 12 miles. Neu­tron stars them­selves are not usu­ally dan­ger­ous—9 out of 10 will be­come trans­formed into a pul­sar, which does just one thing: It ro­tates ex­tremely fast un­til all its re­main­ing en­ergy has been used up. How­ever, not ev­ery neu­tron star leads such a peace­ful ex­is­tence. A small num­ber of them mu­tate into an in­ter­stel­lar hot­head—a mag­ne­tar!

They have “prop­er­ties that can­not be un­der­stood in the lab­o­ra­to­ries on Earth,” says Dr. Michael Gabler of Ger­many’s Max Planck In­sti­tute for As­tro­physics. If any­thing, the con­di­tions in­side a mag­ne­tar can only be cal­cu­lated us­ing complex mod­els. And these re­veal that a mag­ne­tar’s cen­ter is three times denser than an atomic nu­cleus. In fact, the in­te­rior of a mag­ne­tar is so dense that a piece of the neu­tron star the size of a sugar cube would weigh hun­dreds of mil­lions of tons on Earth. In­side, the tem­per­a­ture is over 1.8 bil­lion de­grees Fahren­heit. In ad­di­tion, a mag­ne­tar is per­fectly smooth. Its grav­ity does not per­mit pro­tru­sions to form. If Mount Everest were de­posited onto one of these ro­tat­ing mag­nets, it would be­come com­pressed to the size of an ant.


The mag­netic fields of these zom­bie stars are by far the strong­est in the uni­verse. On the sur­face they reach a field strength of sev­eral quadrillion gauss. In com­par­i­son, the mag­netic field of our Sun has an intensity of around 1 gauss, while at the North Pole of Earth the value is 0.6 gauss. If a mag­ne­tar were to come within 125,000 miles of Earth, its mag­netic field would be so strong that all of the mag­netic stripes on credit cards would be erased in one fell swoop. A mag­ne­tar could at­tract an iron train on the Moon from a dis­tance of 50,000 light-years. But what would hap­pen if a mag­ne­tar ap­proached Earth from the vicin­ity of the Moon?


Re­searchers give us the all- clear. To be sure, field strength of 1 bil­lion gauss would im­me­di­ately wipe out hu­man­ity, but, ac­cord­ing to ex­perts, it would never ac­tu­ally come to that. The rea­son: In or­der to reach such intensity, the mag­ne­tar would have to prac­ti­cally be in sight. But at this dis­tance its mag­netic force would be so strong that the struc­ture of the atoms and mol­e­cules in our bod­ies would be re­ar­ranged—ba­si­cally we wouldn’t die, we’d cease to ex­ist.


A much more re­al­is­tic threat to Earth is posed by a mag­ne­tar’s in­di­rect in­flu­ence: Mag­ne­tars are ac­tu­ally deadly ra­di­a­tion can­nons that fire huge gamma-ray bursts across the uni­verse. No mat­ter how far away it’s com­ing from—a sin­gle di­rect hit could mean the end of hu­man­ity. If such an im­mense jet of en­ergy were to shoot through space, “We re­ally wouldn’t want Earth to be in its way,” says Univer­sity of Sydney physics pro­fes­sor Peter Tuthill.

Sur­pris­ingly, Earth has been shot at by these ag­gres­sive zom­bie stars dozens of times—even if they were ul­ti­mately only warn­ing shots. One struck Earth on De­cem­ber 27, 2004. From 50,000 light- years away, the mag­ne­tar SGR 1806-20 fired its “ray gun” at our at­mos­phere. The re­sult: The beam knocked out 15 satel­lites and long­wave ra­dio com­mu­ni­ca­tion was mas­sively dis­rupted. No one can tell if SGR 1806-20 is ca­pa­ble of do­ing even more dam­age. But this is nei­ther the most ob­vi­ous nor the largest mag­ne­tar in the Milky Way. That would be 1E 1048.1-5937 in the Ca­rina con­stel­la­tion—a mag­ne­tar that’s a mere 8,800 light-years away from Earth. And then there’s CXOU J164710.2- 45516, which was found in the Wester­lund 1 star clus­ter that is 16,000 light-years away. It’s still unclear how de­struc­tive a di­rect hit from a mag­ne­tar can be, es­pe­cially one a lot larger and closer than the al­ready de­struc­tive SGR 1806-20. Ac­cord­ing to state­ments made by Univer­sity of Kansas as­tro­physi­cist Adrian Melott, it’s con­ceiv­able that an ex­tremely pow­er­ful gamma-ray burst strik­ing Earth could evap­o­rate up to 25% of the ozone layer within a few sec­onds. “The oceanic food webs would col­lapse, agri­cul­tural crises and famines would de­velop. Per­haps it would even be the start of a new mass ex­tinc­tion,” says Melott. It wouldn’t be the first time…

ASTRO­NOM­I­CAL DWARF Com­pared to other ce­les­tial bod­ies, mag­ne­tars are tiny— but their mass is all the greater. Just one tea­spoon of a mag­ne­tar’s mat­ter would weigh hun­dreds of mil­lions of tons on Earth.



Max Planck In­sti­tute for As­tro­physics

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