On April 10, 2019, the Event Horizon Telescope (EHT) team of radio astronomers produced the first photograph of the M87 Galaxy’s black hole the size of our solar system described by astronomers as the “gates of hell and the end of spacetime.” The now iconic image captured light from the entire universe wrapping around the object in a nested series of rings.
As Peter Galison of Harvard, an EHT collaborator said, “As we peer into these rings, we are looking at light from all over the visible universe, we are seeing farther and farther into the past, a movie, so to speak, of the history of the visible universe.”
Galison said he thinks the image unveiled will be more compelling evidence of the existence of black holes to the public than some of the more technical data. “It’s amazing to be able to say, here’s the black hole, the size of our solar system, and bigger, and it has the mass of six and a half billion suns,” he said.
“The image of a black hole actually contains a nested series of rings,” said Michael Johnson of the Harvard-Smithsonian Center for Astrophysics, not unlike the rings that form around your bathtub drain in a study published in the March 18 edition of the journal Science Advances.
“Understanding the intricate details of this historic experimental observation has forced theorists like myself to think about black holes in a new way,” said co-author Andrew Strominger, a professor of physics and the Assistant Director of Theory at the Black Hole Institute. The black hole was an object that was predicted to exist 100 years ago, he said. “And the fact that it’s taken us hundred years to get a clear picture of them is not a measure of how lazy and slow scientists are. It’s a measure of how huge the problem is, and with what precision and depth we’re understanding the universe around us. It’s something I’ve been thinking about my entire scientific life, and now I’ve seen it.”
The image marked the culmination of years of work undertaken by a team of 200 scientists in 59 institutes across 18 countries. The project, to which other scientists at Harvard’s Black Hole Institute also contributed, drew on data collected by eight telescopes whose locations range from Hawaii to the South Pole. In order to construct this image digitally, the team of astronomers at EHT created the equivalent of a lens the size of planet Earth by integrating data from all the telescopes that were part of the project that’s 4,000 times more powerful than the Hubble Space Telescope.
A visualization demonstrating the individual photon rings that make up the first ever image of the supermassive black hole at galaxy M87. (Harvard-Smithsonian Center for Astrophysics)
“What really surprised us was that while the nested subrings are almost imperceptible to the naked eye on images—even perfect images—they are strong and clear signals for arrays of telescopes called interferometers,” says Johnson. “While capturing black hole images normally requires many distributed telescopes, the subrings are perfect to study using only two telescopes that are very far apart. Adding one space telescope to the EHT would be enough.”
New observations during July 2018 with ESO’s Very Large Telescope revealed that the giant elliptical galaxy Messier 87 swallowed an entire medium-sized galaxy over the last billion years. The Event Horizon Telescope (EHT) team theorized that the M87 black hole grew to its massive size by merging with several other black holes. M87 is the largest, most massive galaxy in the nearby universe, and is thought to have been formed by the merging of 100 or so smaller galaxies.. The M87 black hole’s large size and relative proximity, led astronomers think that it could be the first black hole that they could actually “see.”
“A medium-sized galaxy fell through the center of M87, and as a consequence of the enormous gravitational tidal forces, its stars are now scattered over a region that is 100 times larger than the original galaxy!” said Ortwin Gerhard, head of the dynamics group at the Max Planck Institute for Extraterrestrial Physics.
This first-ever image prompted such excitement in the public because black holes are a cultural phenomenon imbued with metaphor and mythology, according to Galison. “There’s something paradoxical, intriguing, frightening, and imagination-provoking about black holes,” he said.
The Harvard scientists say they think new discoveries are still on the horizon. “There are some real questions about destruction, what’s inside a black hole, and so on, that we might get to the very edge of — or even probe — with this Event Horizon Telescope,” Strominger said.