Independent technique validates landmark M87* image

The 2019 Event Horizon Telescope (EHT) image was the work of hundreds of scientists and captured the first direct view of a black hole’s shadow—becoming one of the most recognized scientific images of the modern era. A team of four from CSIRO, Australia’s national science agency, has developed a powerful new imaging technique that validated the landmark 2019 image of the black hole at the center of galaxy M87.

CSIRO astronomer and lead author Dr. Samuel Lai explained the challenge of imaging a distant black hole. “It is like standing in your backyard and trying to take a photo of a doughnut on the moon,” Lai said.

Matching the original image independently

The new approach to analyzing the EHT data, published in Nature, reduces the effects of calibration errors and subjective image-processing decisions, which have challenged astronomers for decades.

“Our small Australian team developed advanced machine learning and artificial intelligence techniques to capture information about the black hole’s structure and filter out atmospheric interference,” Lai explained.

“When we applied it to the original Event Horizon Telescope dataset, we found a black hole almost identical in size and shape to the historic EHT image. Importantly, our model had no idea what a black hole looked like when we applied it to the M87 data.

“This is the first truly independent validation of the EHT image, an important step in the scientific process.”

Removing errors from telescope data

While the EHT’s first image of M87’s black hole transformed our understanding of these extreme objects, scientists have questioned how much the final image may have been influenced by the processing methods needed to reconstruct pictures from sparse telescope measurements.

To address this, the CSIRO team developed elegant mathematical algorithms to eliminate biases and calibration errors.

CSIRO astronomer and project leader Dr. Nithyanandan Thyagarajan used his experience in solving similar challenges in synchrotron experiments to build the new technique.

“In order to image certain astronomical objects like distant black holes, we need very big telescopes, which isn’t practically possible. So, groups like the Event Horizon Telescope Collaboration connect telescopes across the globe to mimic a telescope the size of the planet, a technique called very long baseline interferometry,” Thyagarajan said.

“Creating an image this way is tricky and can introduce errors and biases that could lead to questions about the accuracy of the image. Our technique combines triplets rather than the standard pairs of telescope data to eliminate those errors.”

Confidence in the ring structure

The findings strengthen confidence that the ring surrounding M87’s central black hole is a genuine astrophysical feature rather than an artifact introduced during image reconstruction.

Event Horizon Telescope Collaboration director Dr. Laurent Loinard said studies like this are at the heart of the scientific process, providing valuable independent validation of the Event Horizon Telescope results.

“It is extremely gratifying to see that GenDIReCT, an elegant, entirely independent method, recovers the ring structure of M87* across several years, in excellent agreement with the EHT Collaboration’s published results. Studies like this strengthen our confidence in what we have learned about black holes, and enrich the toolkit available to the whole community,” Loinard said.

Thyagarajan said the CSIRO-developed technique has the potential to improve medical imaging and mapping earthquakes—an out-of-this-world solution to real-world problems.

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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