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Four years ago, astronomers released the first image of a black hole: a donut of red light surrounding the empty dark hole at the center of the giant galaxy M87, 55 million light-years away in the constellation Virgo.
The image shows what astronomers, and all of us, can imagine: a celestial entity so massive that its gravity distorts space-time, drawing matter, energy and even light into a bottomless vortex. The image was released on April 10, 2019, by an astronomical team called the Event Horizon Telescope, which is named as the boundary of no return around a black hole.
Now a subset of the team, led by Lia Medeiros of the Institute for Advanced Study in Princeton, has used artificial intelligence to process the original data and produce a better version of the image.
The new images, they say, will clear the way for how well the black hole in M87 fits Einstein’s general theory of relativity, which first predicted the existence of black holes. Dr Medeiros and his colleagues published the new images on Thursday in the Astrophysical Journal Letters.
Perhaps the image will join its ancestors in 2019 in the photography collection of the Museum of Modern Art in New York. Both images are based on observations made in April 2017. The Event Horizon team effectively created an Earth-sized telescope by combining data from five remote radio telescopes from the South Pole, France, Chile and Hawaii, using a technique called very long baseline interferometry.
The resulting instrument is powerful enough to resolve details as small as orange on the moon’s surface or a cosmic pinprick that doesn’t exist – with a mass of 6.5 billion suns – 55 million light years away. But gaps in the network create uncertainty. “We use machine learning to fill in the gaps,” Dr. Medeiros said in an interview.
His team trained neural networks to identify black holes by giving AI simulations of all types of black holes that fit Einstein’s equation.
In a better version, Dr. Medeiros said, the donut of doom – the visible radiation from the material falling into the hole – is thinner than the original. And the empty spot in the middle of the donut looks blacker and bigger, adding to the idea that there is a black hole in there.
The team has analyzed the new images to get a better estimate of the M87 black hole’s mass, but they are not yet ready to discuss it.
In the meantime the work continues, with the Event Horizon network even bigger. (Three new telescopes have been added.) Every April, when M87 and the center of our galaxy (home to smaller black holes) come into view, the Earth-sized eye looks back into the darkness.
“People are in telescopes,” said Dr Medeiros.
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