While sometimes we get lucky and find things that match theory, sometimes we also find things that prove our theories are wrong or at least incomplete. Case in point: the binary system MAXI J1820+070. This system contains a regular star and also a black hole that formed from the death of a star. As often happens, the gravitational pull of the black hole is stripping material off its neighbor.

As we didn’t think should happen, the orbits of these two stars and the spin axis of the black hole aren’t lined up. Instead, the black hole appears tilted about 40 degrees. For comparison, Saturn and its ring system are only tilted 27 degrees. The lead author of this paper, Svetlana Berdyugina, puts it this way: The difference of more than 40 degrees between the orbital axis and the spin of the black hole was completely unexpected. … This finding challenges current theoretical models of black hole formation. 

This work appears in the journal Science.

The tilt of the black hole is highlighted by jets that appear in X-ray images. The tilt of the incoming material from its companion was measured by looking at how the light scattered off the disk using a technique called polarimetry.

Normally, results like this are just super cool because they tell us the universe isn’t behaving as expected. This discovery is also troubling because the tilts of the system are used to calculate the masses of the objects in the system. If we’ve been assuming the wrong tilt, well, there could be a bunch of black holes out there that we mismeasured.

Science is a process, folks. And sometimes it requires a step sideways and a good sit while we figure out if we can keep going forward on the path we’re on or if we need to go back and try again from a different direction. Or in this case, a different tilt.

More Information

University of Freiburg press release

“Black hole spin–orbit misalignment in the x-ray binary MAXI J1820+070,” Juri Poutanen et al., 2022 February 24, Science