Assessing the impact of instrument noise and astrophysical fluctuations on measurements of the first black hole photon ring

Understand

Currently envisioned extensions of the Event Horizon Telescope to space will soon target the black hole photon ring: a narrow ring-shaped imprint of a black hole's strong gravity produced in its images by highly bent photon trajectories.

• In principle, the shape of the photon ring encodes information about the geometry of the underlying black hole spacetime.
• In practice, however, whether or not this information can be extracted from the ring shape depends on several factors, ranging from the astrophysical details of the emitting source (such as the magnitude of its plasma fluctuations) to the specific configuration of the interferometric array (such as the separation between its telescopes, or the level of noise in its instruments).
• Here, we employ a phenomenological model to assess the impact of astrophysical fluctuations and instrument noise on the inferred shape of the photon ring.