Sharpest new images of black holes “likely to reveal new properties”

Scientists have captured the highest-resolution images of black holes ever taken from the ground.

These two black holes, located at the heart of our galaxy and another galaxy called M87, were imaged by the Event Horizon Telescope (EHT) Collaboration, according to a new article in The Astronomical Journal.

The new, sharper images of the black holes were created by detecting light at a frequency of 345 GHz, which could be combined with existing images of black holes taken with 230 GHz light.

The new images have 50 percent higher resolution than previous ones and show more details of the areas around the event horizon of the black holes.

“With the EHT, we saw the first images of black holes by detecting radio waves at 230 GHz, but the bright ring we saw, created by the bending of light in the black hole’s gravity, still looked blurry because we were at the absolute limit of image sharpness,” study co-author Alexander Raymond, a former postdoctoral fellow at the Center for Astrophysics | Harvard & Smithsonian (CfA) and currently an astrophysicist at NASA’s Jet Propulsion Laboratory (NASA-JPL), said in a statement.

“At 345 GHz, our images will be sharper and more detailed, which in turn will likely reveal new properties, both those that were previously predicted and some that may not have been predicted.”

These more detailed images will allow astrophysicists to better measure the shape and size of black holes.

These black holes – M87* and Sgr A* – are supermassive black holes found at the center of galaxies. These black holes are incredibly dense regions of space where the gravitational pull is so strong that not even light can escape. Unlike stellar-mass black holes, which are formed when massive stars collapse, supermassive black holes have masses ranging from millions to billions of solar masses.

Sgr A* or Sagittarius A* is located at the center of the Milky Way, while M87* is located at the center of a galaxy called M87 (Messier 87), 5 million light-years from Earth.

M87* is an exceptionally massive black hole, estimated to have a mass about 6.5 billion times that of our Sun, while Sgr A* has a mass about 4.3 million times that of our Sun.

M87* rose to global fame in April 2019 when it became the first black hole to be directly imaged by the Event Horizon Telescope, revealing a bright ring of hot gas and dust swirling around the dark black hole. In May 2022, the Event Horizon Telescope collaboration released the first image of Sgr A*

These images, in the new 345 GHz frequency, were taken using a network of multiple radio dishes around the world. This allowed the researchers to perform very long baseline interferometry (VLBI) to spy on the black holes. The new frequency images also make it possible to combine the frequencies in a single image, creating a “color view” of the black holes.

“To understand why this is a breakthrough, you have to consider the additional detail you get when you go from black-and-white photos to color photos,” study co-author Sheperd “Shep” Doeleman, an astrophysicist at the CfA and the Smithsonian Astrophysical Observatory (SAO) and founding director of the EHT, said in the statement.

“This new ‘color vision’ allows us to separate the effects of Einstein’s gravity from the hot gas and magnetic fields that feed the black holes and trigger powerful jets that flow across galactic distances.”

Researchers hope to be able to create videos of black holes using 345 GHz light for the first time in the future.

“The successful observation of the EHT at 345 GHz is a major scientific milestone,” said Lisa Kewley, director of CfA and SAO. “By pushing the limits of resolution, we are achieving the unprecedented clarity in black hole imaging that we promised early on and setting new and higher standards for the power of Earth-based astrophysics research.”

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References

Raymond, AW, Doeleman, SS, Asada, K., Blackburn, L., Bower, GC, Bremer, M., Broguiere, D., Chen, M.-T., Crew, GB, Dornbusch, S., Fish, VL, García, R., Gentaz, O., Goddi, C., Han, C.-C., Hecht, MH, Huang, Y.-D., Janssen, M., Keating, GK, … Zhao, S.-S. (2024). First very long baseline interferometry detections at 870 μm. The Astronomical Journal, 168(3), 130. https://doi.org/10.3847/1538-3881/ad5bdb