Gizmodo's Funky Black Hole Is Spinning Tilted says:
A team of astronomers recently observed an askew black hole just 10,000 light-years from Earth. The black hole’s spin axis is out of alignment with the plane of debris orbiting it by at least 40 degrees, the most extreme misalignment of its kind yet seen by astronomers.
The system is called MAXI J1820+70, and it contains a small black hole (about eight times more massive than the Sun) and a star that’s about half the size of the Sun. Astrophysicists recently calculated that the black hole, an incredibly dense object with a gravitational field so intense that not even light can escape, is spinning at an awkward angle compared to stuff orbiting it; the researchers think its tilt may be a relic of how the object was born, in the violent death of a star.
“The main result is that, for the first time, we measure a large (>40 degrees) misalignment between the black hole spin and the orbital spin,” said Juri Poutanen, an astrophysicist at the University of Turku in Finland and the paper’s lead author, in an email to Gizmodo. “In this case, the likely formation channel is a large kick (due to asymmetric neutrino emission) to the black hole during the collapse of the core of a massive star.”
and then links to the Science Perspective article A crooked spinning black hole which links to Juri Poutanen et al. (2022) Black hole spin–orbit misalignment in the x-ray binary MAXI J1820+070 which seems to have an arXiv preprint as Extreme black hole spin--orbit misalignment in X-ray binary MAXI J1820+070
Question: How did astronomers "measure a large (>40 degrees) misalignment between the black hole spin and the orbital spin" of MAXI J1820+70?
How direct/indirect is this "measurement" of >40 degrees? Is it something that can be visualized in an image somehow?