This famous black hole has gotten bigger and darker
Four years ago, astronomers published the very first image of a black hole: A reddish, puffy donut of light surrounding a dark, empty hole in the center of the giant galaxy M87, which lies 55 million light-years away in the constellation Virgo.
The image made visible what astronomers, and the rest of us, could only imagine: a celestial entity so massive that its gravity warped spacetime, pulling matter, energy and even light into its bottomless vortex. The image was released on April 10, 2019 by an astronomy team called the Event Horizon Telescope, so named for the limit of no return around a black hole.
Now a subset of that team, led by Lia Medeiros of the Institute for Advanced Study in Princeton, NJ, has used artificial intelligence to reprocess the original data and produce a significantly improved version of the image.
The new image, they say, will strengthen constraints on how well M87’s black hole fits Einstein’s general theory of relativity, which first predicted the existence of black holes. Dr. Medeiros and his colleagues published the new image Thursday in Astrophysical Journal Letters.
Perhaps the image will join its 2019 ancestor in the photography collection of the Museum of Modern Art in New York. Both images are based on observations that were made in April 2017. The Event Horizon team effectively created a telescope as large as Earth by combining data from five radio telescopes as far away as the South Pole, France, Chile and Hawaii, using a technique called very long baseline interferometry.
The resulting instrument was powerful enough to resolve details as small as an orange on the moon’s surface or a cosmic sting of nothingness – with the mass of 6.5 billion suns – 55 million light-years away. But gaps in the network have led to uncertainties. “We used machine learning to fill in the gaps,” Dr. Medeiros said in an interview.
His team trained the neural network to recognize the black hole by feeding AI simulations of all kinds of black holes that conform to Einstein’s equations.
In the upgraded version, Dr. Medeiros said, the donut of doom — the visible radiation of matter falling into the hole — is thinner than in the original. And the empty spot in the center of the donut appears blacker and larger, reinforcing the idea that there really is a black hole there.
The team is already analyzing the new image to get a better estimate of the mass of M87’s black hole, but they’re not ready to discuss that yet.
In the meantime, the work continues, with an even larger Event Horizon network. (Three new telescopes have been added.) Each April, when M87 and the center of our galaxy (home to a smaller black hole) come into view, the Earth-sized eye renews its gaze in the darkness.
“People are at telescopes,” Dr. Medeiros said.