The breakthrough image of a supermassive black hole was unveiled at at a series of simultaneous press conferences held around the world on Wednesday. The black hole photographed in the image lies 55 million light-years away in a galaxy known as Messier 87 (M87). It has been estimated to have a mass of more than six billion solar masses.
The image of the black hole has been analysed in six studies published in the Astrophysical Journal Letters.
The first direct image of a black hole required telescopes of unprecedented precision and sensitivity. The realization of this telescope – the Event Horizon Telescope (EHT) – required connecting a worldwide network of eight ground-based radio telescopes deployed at a variety of challenging high-altitude sites. These locations included volcanoes in Hawaii and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the French Alps, the Chilean Atacama Desert, and Antarctica.
“We are giving humanity its first view of a black hole — a one-way door out of our universe,” said EHT project director and astrophysicist Sheperd S. Doeleman in a statement issued on the occasion. “This is a landmark in astronomy, an unprecedented scientific feat accomplished by a team of more than 200 researchers.”
NASA has also described this accomplishment as “a historic feat” in a Twitter post.
Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and super-heating any surrounding material so that it glows. Albert Einstein’s theory of general relativity predicts that the heated material will illuminate the extremely warped spacetime, making a dark shadow visible.
“If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained the chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands.
“This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and allowed us to measure the enormous mass of M87’s black hole.”
The EHT observations indeed do reveal a ring-like structure with a dark central region — the black hole’s shadow. The ring appears in multiple separate observations using different imaging methods that were analysed independently from each other.
“Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” remarked Luciano Rezzolla, professor for theoretical astrophysics at Goethe University.
Karl Schuster, director of IRAM and member of the EHT board, said that bringing together the best radio telescopes on four continents enabled them to reach an unprecedented sensitivity and spatial resolution, and allowed scientists to carry out measurements at the very limit of what was physically possible.
“After decades of research where we could postulate black holes only indirectly, albeit with great precision, it was not until LIGO in 2015 that we were able to make the impact of merging black holes on space-time ‘audible,'” explained Michael Kramer, Director at MPIfR and co-PI of the ERC Black Hole Cam project. “Now we can finally ‘see’ them, and investigate the extreme warping of spacetime they are causing in a unique way.”
“In the future, scientists far beyond our field will clearly remember a time before and after this discovery,” predicted Anton Zensus, Chair of the EHT Collaboration Board.
The construction of the EHT was the effort of many years of work, and is an example of global teamwork by researchers from various countries around the world. Thirteen partner institutions worked together to create the EHT. Key funding was provided by the EU’s European Research Council (ERC), the US National Science Foundation (NSF), and funding agencies in East Asia.