“It turns out that there are only really three things that you can measure about the properties of a black hole: its mass, its spin, and its charge,” says Sivakoff. “I’m really interested about the ability for IXPE to give us a new way of measuring the spin, and possibly even checking to see if there are any changes to that spin over a long enough time.”
Black holes make up about 40% of the dark matter in the universe, but only recently were astronomers able to photograph one. The data IXPE will bring back will help determine whether black holes once actively fed on their neighbors and make it easier for scientists to study the particles that exist around these powerful objects. With x-ray polarization, it’s also possible to map the inner edge of a black hole by measuring its angular momentum, or spin.
Since supermassive black holes and neutron stars are the remnants of massive stars that lived fast and died young, IXPE’s mission could also give us a glimpse of how galaxies evolve, Sivakoff adds.
Herman Marshall, a research scientist at the MIT Kavli Institute for Astrophysics and Space Research and a co-investigator for IXPE, says measuring polarization “is like putting up a mirror, you might say, to the unseen part of the galaxy.” Here’s hoping that once IXPE turns its eyes toward the stars, the galaxy won’t mind parting with a few more of its secrets.