Late last December, the biggest explosion ever observed in the Milky Way was detected by our orbiting observatories. In 0.25 seconds, a slow-spinning pulsar 30,000-50,000 light-years away emitted more energy than our sun does in 250,000 years.
Amazingly, this over-achieving stellar corpse is still there; it didn’t blow itself up somehow. Rather, the explosion was an event not unlike the solar flares we see rising from our own star, though it’s a much more exotic variety of flare. What the nature of this flar is exactly I don’t understand. Apparently the immensely-strong magnetic fields of these incredible objects get so wound up something finally “snaps”, and all that pent-up energy is released in a fraction of a second. I’m not sure if some of the energy release involves actual material being ejected from the pulsar, as we see with solar flares, or if it’s all due to particles being conjured up from the vacuum, or some mixture of the two. The popular descriptions leave me struggling for analogies.
So what’s going on here? Why are these magnetars different than other pulsars? What gives them such incredibly huge magnetic fields? Now that I think of it (a perilous exercise), how is it that a giant ball of neutrons has much of a magnetic field at all? I know individual neutrons have net magnetic moments because they’re a composite of charged quarks, which themselves spin, but it seems unlikely to me that all the neutrons making up a neutron star would be aligned in such a way as to make their indivdual magnetic fields add up constructively. Maybe I’m wrong about that, I don’t know. Maybe there is a lot of moving charge in a neutron star that it’s name belies; again, I don’t know. Finally, how do twisting magnetic field lines produce such a colossal explosion? What’s exploding, exactly?
Was the energy released isotropically from the magnetar? Or does the direction of the magnetic field of the star specify a direction for the release of energy?
From the last of Squink’s cites, it appears that the periodicity in the damping peaks of the burst, which match the rotational period of the source, suggest the energy emanates from a localized region that is coupled to the surface of the neutron star.
Wikipedia says magnestars can have fields in excess of 10 gigateslas (compared to 30-50 microteslas for the Earth’s field, or 1 tesla for a reasonably powerful permanent magnet.) If a field that intense could be generated even on a small scale, what would it do? Would it rip atomic matter apart into plasma? I’m thinking of the time Wile E. Coyote built his “1,000,000,000,000 volt” electromagnet and ended up dragging satellites down from orbit.
I’ve never heard of a field that strong from a permanent magnet, but that’s relatively routine for powerful (and re-useable) laboratory electromagnets. Note that that’s still quite powerful enough that you want to take your credit card and pocketknife out of your pockets before entering the lab.
I used to work with a ~5 Tesla NMR spectrometer that would suck a wrench right out of your hands (which actually happened to somebody once, damaging the bottle holding the LN[sub]2[/sub] that kept the superconducting coils chilled). Needless to say, we left our wallets in the next room. The computer hooked up to the thing had to be shielded with “mu metal” boxes. You could lift the shield off of the monitor, and the image projected on the screen would get completely distorted; you could actually see the effects of the electron beam being dragged toward the side of the room the magnet sat in. This was a fairly pedestrian unit as NMR spectrometers go.