Using NASA’s Imaging X-ray Polarimetry Explorer (IXPE) satellite, astronomers have been able to measure and map polarized X-rays from the remains of a star some 11,000 light-years away .
According to experts, the moment in which it exploded, after running out of fuel and collapsing in on itself, was around the year 1680, at which time it would have become one of the brightest objects in the sky, albeit briefly. However, there are no historical records to confirm this.
NASA and the Italian Space Agency selected this remnant specifically because its shock waves are some of the fastest in the Milky Way.
“Without IXPE, we’ve missed crucial information about objects like Cassiopeia A,” explained Pat Slane, an astronomer at the Harvard-Smithsonian Center for Astrophysics. “This result is teaching us about a fundamental aspect of the debris from this exploded star: the behavior of its magnetic fields.”
Despite this enormous speed, the particles entrained by the shock waves in Cassiopeia A do not fly away from the supernova remnant because they are trapped by the magnetic fields in the wake of the shocks. These particles spin and spiral, so the electrons emit a type of light called a synchrotron, which is polarized and can be studied.
Thanks to it, scientists can reverse engineer what happens inside Cassiopeia A at very small scales, something that would be almost impossible to observe otherwise.
The IXPE data show that X-ray magnetic fields tend to align in radial directions even very close to shock fronts.
“These IXPE results were not what we expected, but as scientists we love to be surprised,” said Jacco Vink, an astronomer at the University of Amsterdam and co-author of the paper published in the Astrophysical Journal . “The fact that a smaller percentage of the X-ray light is polarized is a very interesting and previously undetected property of Cassiopeia A.”
Referencia: Jacco Vink et al. 2022. X-ray polarization detection of Cassiopeia A with IXPE. ApJ, in press; arXiv: 2206.06713
