Cutting a path ...

Black holes cast a shadow on the image of bright surrounding material because their strong gravitational field can bend and trap light. The shadow is bounded by a bright ring of light, corresponding to photons that pass near the black hole before escaping. The ring is actually a stack of increasingly sharp subrings, and the n-th subring corresponds to photons that orbited the black hole n/2 times before reaching the observer. This animation shows how a black hole image is formed from these subrings and the trajectories of photons that create the image. Credit: Center for Astrophysics, Harvard & Smithsonian

Science has figured out how to get razor-sharp images of black holes, something not even conceived of just one year ago prior to getting the first pix of M87.

Last April, the Event Horizon Telescope (EHT) sparked international excitement when it unveiled the first image of a black hole. Today, a team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.

"The image of a black hole actually contains a nested series of rings," explains Michael Johnson of the Center for Astrophysics, Harvard and Smithsonian (CfA). "Each successive ring has about the same diameter but becomes increasingly sharper because its light orbited the black hole more times before reaching the observer. With the current EHT image, we've caught just a glimpse of the full complexity that should emerge in the image of any black hole."

Because black holes trap any photons that cross their event horizon, they cast a shadow on their bright surrounding emission from hot infalling gas. A "photon ring" encircles this shadow, produced from light that is concentrated by the strong gravity near the black hole. This photon ring carries the fingerprint of the black hole—its size and shape encode the mass and rotation or "spin" of the black hole. With the EHT images, black hole researchers have a new tool to study these extraordinary objects.

How cool is that?

M87 raw image

What M87 will look like after intense data collection and image processing.

Fig. 1 Time-averaged image of a GRMHD simulation of M87.

This model has parameters chosen to be consistent with the 2017 EHT data and corresponds to the high magnetic flux “magnetically arrested disk” accretion state. It has M = 6.2 × 109M⊙, a/M = 0.94, θobs = 163°, rhigh = 10, and mass accretion rate matching the 1.3-mm flux density (5). The spin axis points left when projected onto the image. The time average was performed over 100 snapshots produced from uniformly spaced GRMHD fluid samples over a time range of 1000M (approximately 1 year). Although visually prominent, the thin, bright ring contains only ~20% of the total image flux density.

Stellar without question.