New technology makes images of black holes sharper

When scientists unveiled humanity’s first historic image of a black hole in 2019—depicting a dark core surrounded by a fiery aura of matter falling toward it—they believed even richer images and insights were waiting to come. Extract from the data.

The simulations predict that, hidden by this bright orange glow, there should be a thin, bright ring of light created by photons thrown from the back of the black hole by its intense gravity.

Now, a team of researchers has combined theoretical predictions and sophisticated image processing algorithms to “remaster” the original images of the supermassive black hole at the center of the M87 galaxy*, first captured by the Event Horizon Telescope (EHT ) in 2019. Their results , published today in The Astrophysical Journal, are consistent with theoretical predictions and offer new ways to explore these mysterious objects believed to lie at the heart of most galaxies.

“The approach we took was to leverage our theoretical understanding of what these black holes look like to build a fitted model for the EHT data,” says Dominic Pesce, co-author of the study based at the Center for Astrophysics | Harvard & Smithsonian and member of the EHT collaboration. “Our model breaks down the reconstructed image into the two elements that interest us most, so that we can study the two elements individually instead of mixed. »

The result was made possible because the EHT is a “computational instrument at its core,” says Avery Broderick, who led the study and holds the Delaney Family John Archibald Wheeler Professorship at the Perimeter Institute. “It depends as much on algorithms as on steel. State-of-the-art algorithmic developments allowed us to examine key features in the image while rendering the rest in the native resolution of EHT. »

To achieve this result, the team used imaging software they developed called THEMIS, which allowed them to isolate distinct features of the ring from the original observations of the black hole M87* – as well as revealing the telltale imprint of a powerful jet that blowing outwards. from the black hole.

By essentially “peeling off” elements of the images, says co-author Hung-Yi Pu, an assistant professor at National Taiwan Normal University, “the environment around the black hole can be clearly revealed.”

Black holes were long thought to be invisible until scientists brought them out of hiding with a global network of telescopes known as the EHT. Using eight observatories on four continents, all pointed at the same spot in the sky and linked by nanosecond synchronization, EHT researchers observed two black holes in 2017.

The EHT collaboration first revealed the supermassive black hole in M87* in 2019. Later in 2022, they revealed the relatively small but tumultuous black hole at the heart of our own Milky Way galaxy, called 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; the black hole M87*, for example, is 2 quadrillion (ie two followed by 15 zeros) times more massive than Earth.

The M87* image that the researchers revealed in 2019 was a landmark find, but the researchers believed that they could still refine the image and gather new information. By applying their new software technique to the original 2017 data, the team was able to focus the binding power of the data on the phenomena that theories and models predict lurk beneath the surface.

The newly developed technique hardly shows its promise on existing EHT data from 2017.

“As we continue to add more telescopes and build the next-generation EHT, the increased quality and quantity of data will allow us to place more definitive constraints on these signatures that we are only now getting our first glimpse of.” says co-author Paul Tiede, CfA astrophysicist and EHT fellow at Harvard University’s Black Hole Initiative.

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