A black hole ready for its close-up

The Photon Ring: A black hole ready for its close-up

The emission from M87 has now been resolved into a bright, thin ring (orange color map) arising from the infinite sequence of additional images of the emission region, and the more diffuse primary image produced by the photons hitting Earth directly (in blue contours). When viewed at the Event Horizon Telescope’s imaging resolution, the two components become blurred. However, by separately searching for the thin ring, it is possible to sharpen the view of M87 and isolate the strong gravity fingerprint. Photo credit: Broderick et al

When scientists unveiled humanity’s first historical image of a black hole in 2019 – showing a dark core surrounded by a fiery aura of matter falling on it – they believed there were even richer images and insights waiting to be teased out of the data.

Simulations predicted that behind the glare of the diffuse orange glow should be hiding a thin, bright ring of light generated by photons thrown around the back of the black hole by its intense gravity.

A team of researchers led by astrophysicist Avery Broderick used sophisticated imaging algorithms to essentially “remaster” the original images of the supermassive black hole at the center of the M87 galaxy.

“We turned off the searchlight to see the fireflies,” said Broderick, an associate faculty member at the Perimeter Institute and the University of Waterloo. “We were able to do something profound – resolve a fundamental signature of gravity around a black hole.”

By essentially “detaching” elements of the images, says co-author Hung-Yi Pu, an assistant professor at National Taiwan Normal University, “the black hole’s surroundings can then be made clearly visible.”

To achieve this, the team used a new imaging algorithm within the Event Horizon Telescope (EHT) analysis framework THEMIS to isolate and extract the distinctive ring feature from the original observations of black hole M87 – as well as the tell-tale footprint of a powerful one to recognize jet jets from the black hole to the outside.

The researchers’ findings confirm both theoretical predictions and offer new ways to study these mysterious objects thought to reside at the heart of most galaxies.

Black holes were long thought to be invisible until scientists lured them out of hiding with a global network of telescopes, the EHT. Using eight observatories on four continents, all pointing to the same point in the sky and linked together with nanosecond timing; In 2017, EHT researchers observed two black holes.

The EHT collaboration first revealed the supermassive black hole in M87 in 2019, and then in 2022 the comparatively small but turbulent black hole at the heart of our own Milky Way galaxy, dubbed Sagittarius A* (or Sgr A*). Supermassive black holes occupy the center of most galaxies, packing an incredible amount of mass and energy into a small space. Black hole M87, for example, is two quadrillion (that’s a two followed by 15 zeros) times heavier than Earth.

The M87 image scientists, unveiled in 2019, were a milestone, but researchers thought they could sharpen the image and gain new insights by working smarter, not harder. They applied new software techniques to reconstruct the original 2017 data in search of phenomena that theories and models predicted lurked beneath the surface. The new resulting image shows the photon ring made up of a series of progressively sharper sub-rings, which the team then stacked to get the full picture.

“The approach we took involved using our theoretical understanding of how these black holes Try to build a fitted model for the EHT data,” said Dominic Pesce, a team member at the Center for Astrophysics | Harvard & Smithsonian. “This model breaks down the reconstructed image into the two parts that matter most to us, so that we can study both pieces separately rather than together.”

The result was possible because the EHT is a “computer instrument at heart,” said Broderick, who holds the Delaney Family John Archibald Wheeler Chair at Perimeter. “It is as dependent on algorithms as it is on steel. Cutting-edge algorithmic developments have allowed us to examine key features of the image while the rest is rendered in the native resolution of the EHT.”

The researchers’ findings were published in The Astrophysical Journal.


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More information:
Avery E. Broderick et al., The Photon Ring in M87*, The Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac7c1d

Citation: The photon ring: A black hole ready for its close-up (2022, August 16), retrieved August 16, 2022 from https://phys.org/news/2022-08-photon-black-hole-ready -close-up .html

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