A team of astronomers found that huge, organized magnetic fields can help fuel some of the most powerful explosions in the universe. But when all is said and done, within minutes the shock wave from this explosion disrupts all magnetic fields.
Some gamma ray bursts (GRBs) occur when giant stars die. Their cores fold up and collapse into a black hole. Shortly after it forms, material falls inward from the surrounding star. There the intense energies drive the generation of huge, powerful, structured magnetic fields. These magnetic fields whip some of the incident material around the black hole and along two long, thin jets. Viewed from Earth, it is these jets that give this event its characteristic flash of high-energy gamma radiation.
But the story doesn’t end there. The rest of the star continues to explode, sending out a shock wave. This shock wave quickly destroys the magnetic field, leaving behind only tangled debris.
At least that’s the theory. But proving the correctness of this theory has been challenging, as astronomers have to measure the magnetic fields shortly after the gamma-ray burst.
A team of astronomers did just that and disclosed their findings in a recent article.
Bath head of astrophysics and gamma-ray expert Professor Carole Mundell said, “We measured a particular property of light – polarization – to directly study the physical properties of the magnetic field that drives the explosion. This is a great result, and it solves a long-standing riddle of these extreme cosmic explosions – a riddle I’ve been studying for a long time. “
The team measured the polarization of the magnetic fields and found, just minutes after taking a GRB, that it was highly polarized – suggesting that it was very structured. Other observations taken hours or days after a GRB show little to no polarization, suggesting that the shock wave had messed up the magnetic field.
Nuria Jordana-Mitjans, PhD student and lead author of the article, said, “This new study builds on our research that showed that the strongest GRBs can be powered by large-scale ordered magnetic fields, but only the fastest telescopes will catch” a fleeting one Look at their characteristic polarization signal before they are lost in the explosion. “
Professor Mundell added, “We must now push the boundaries of technology to examine the earliest moments of these explosions, capture a statistically significant number of bursts for polarization studies, and put our research into the broader context of real-time multimessenger tracking of the extreme universe . “