An independent algorithm recovers M87*'s ring-shaped black-hole shadow

A CSIRO team developed the GenDIReCT imaging method, using closure invariants that are more robust to instrument-calibration errors and validating it on diverse synthetic structures before unblinding Event Horizon Telescope public data from 2017, 2018 and 2021. The algorithm did not require a ring but recovered a 42.2±1.5-microarcsecond shadow; geometric modelling gave 42.3±1.1 microarcseconds, corresponding to about 6.5±0.5 billion solar masses for M87*. Different methods still change ring width, brightness and hotspot location, but the diameter and basic ring structure remain stable. This is an important independent check of the first black-hole image, not proof of every image detail or every prediction of general relativity.