Over the past 40 years, three giant gamma-ray torches have been discovered. A new paper on breaking up magnetars might explain why. Three times in the last 40 years, giant gamma-ray torches have bombarded our corner of space.
These giant torches are not dangerous and last only about a tenth of a second. But they are out of proportion to the usual gamma rays that fly through the universe. Since the discovery of the first of the three torches on March 5, 1979, astronomers have narrowed down the cause of these unusual events: tiny magnetars striking with tremendous energy after an unknown catastrophic event. And now astrophysicists have a new theory about what these catastrophic events are.
Magnetars are a kind of neutron star – super-dense objects that outweigh our sun but are about the size of Staten Island. All neutron stars have intense magnetic fields, but as Live Science has already reported, there are some magnetic outliers – wrapped in magnetic field lines that are strong enough to distort their behavior.
A team of Spanish astronomers has argued in a new article published as a draft online on Aug. 2 in the Preprint journal arXiv that magnetic field instabilities may briefly break up a magnetar and cause it to expose the intense energies in its bowels.(The study has not been reviewed yet.) To arrive at this conclusion, physicists studied the equations that determine the twisted magnetic fields around magnetars.
Mostly these fields are pretty stable. However, there is a “branch” of solutions to the equations that govern the magnetic fields in which the solutions are unstable. And these instabilities are catastrophic.
Unstable fields quickly set up again, the researchers wrote and slammed around until they found a new, stable configuration. They found that this process delivers 30% of the total magnetic field energy across the rigid crust of the mighty little star – waves of magnetic energy large enough to extend from the south shore of Long Island to Connecticut. This energy induces a strong mechanical stress on the hard 1 kilometer thick crust of a magnet.
Our results show that for typical magnetic field strengths … the instability is likely to break much of the crust up to the inner crust, “the researchers wrote.For the largest magnetic fields, the stresses induced in the crust are sufficient to crush the whole crust. And all three magnetars that produced huge torches have unusually large magnetic fields. As soon as a magnetic crust opens, a huge fireball with “ultra-Loravavian” speed or a significant fraction of the speed of light would explode. The whole process would take less than a second, and from Earth we see one of those giant gamma-ray torches that astronomers have discovered since 1979.