We can see the "heartbeat" of a black hole's spinning disk using a light trick we thought came from distant gas clouds.
April 14, 2026
Original Paper
Blueshifted lines from the inner accretion disc's rotation can explain quasar absorption "forests''
arXiv · 2604.09433
The Takeaway
Complex patterns of absorbed light are actually caused by the rotation of the black hole's own disk, not just random gas in space. This gives us a new way to measure the spin and inner workings of the most powerful engines in the universe.
From the abstract
Recent XRISM observations of active galactic nuclei such as PDS 456 have revealed ``forests'' of absorption lines best modeled by five distinct absorption zones with varying large blueshifts. We propose a model in which these relativistic blueshifts originate from the motion of the accretion disc itself, rather than from a clumpy super-Eddington outflow at hundreds of gravitational radii $r_g\equiv GM/c^2$. We demonstrate that thin rings of absorbing material lying just above the accretion disc