The Horizon Telescope (EHT) event – a planetary-scale arrangement of eight ground-based radio telescopes forged through international collaboration – was developed to capture images of one black hole, Today, at coordinated press conferences around the world, EHT researchers are showing that they have succeeded in revealing the first direct visual evidence of a supermassive black hole and its shadow.
This breakthrough was published today in a series of six articles in a special issue of The Astrophysical Journal Letters. The picture shows the black hole in the center of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole is 55 million light-years from Earth and has a mass 6.5 billion times the size of the Sun.
The EHT connects telescopes around the world to form an unprecedented virtual earth-sized telescope. The EHT offers scientists a new way to study the most extreme objects in the universe predicted by Einstein's general theory of relativity during the centenary of the historical experiment that first confirmed the theory.
"We took the first picture of a black hole," said Sheperd S. Doeleman, director of the Center for Astrophysics EHT project Harvard & Smithsonian. "This is an extraordinary scientific achievement made by a team of more than 200 researchers."
Black holes are extraordinary cosmic objects with enormous masses and extremely compact dimensions. The presence of these objects has an extreme impact on their environment, affects space-time and overheats any surrounding material.
"When we dip into a bright region like a disk of glowing gas, we expect a black hole to create a dark region similar to a shadow – something that predicts Einstein's general theory of relativity that we've never seen before," said the Chairman of EHT Science Council Heino Falcke of Radboud University, The Netherlands. "This shadow, caused by the bending of gravity and the capture of light through the event horizon, shows much about the nature of these fascinating objects and has allowed us to measure the enormous mass of the M87 black hole."
Several calibration and imaging methods have shown an annular structure with a dark central area – the shadow of the black hole – that existed beyond several independent EHT observations.
"Once we were sure we had shadowed, we could compare our observations to extensive computer models involving the physics of distorted space, overheated matter, and strong magnetic fields. Many of the features of the observed image are surprisingly consistent with our theoretical understanding, "says Paul T.P. Ho, EHT board member and director of the East Asian Observatory. "This makes us confident in the interpretation of our observations, including our assessment of the mass of the black hole."
"The confrontation of theory with observations is always a dramatic moment for a theorist. It was a relief and a pride to see that the observations matched our predictions so well, "said Luciano Rezzolla, board member of the EHT Board, Goethe University.
The creation of the EHT was an enormous challenge, requiring the modernization and connection of a global network of eight existing telescopes deployed at various demanding high altitude locations. These places included volcanoes in Hawaii and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert and the Antarctic.
The EHT observations use a technique called Very Long Baseline Interferometry (VLBI). It synchronizes the telescope facilities around the world and uses the rotation of our planet to form a giant earth-sized telescope that observes at a wavelength of 1.3 mm. With the VLBI, the EHT can achieve an angular resolution of 20 microseconds – enough to read a New York newspaper in a Parisian café.
The telescopes that contributed to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell telescope, the Large Millimeter Telescope Alfonso Serrano, the submillimeter array, the submillimeter telescope and the South Pole telescope. Petabytes of raw data from the telescopes were combined by highly specialized supercomputers hosted by the Max Planck Institute for Radio Astronomy WITH Haystack Observatory.
European institutions and financial resources played a crucial role in this worldwide effort. The participation of advanced European telescopes and the support of the European Research Council – in particular a grant of € 14 million for the BlackHoleCam project. Support from ESO, IRAM and the Max Planck Society was also key. "This result builds on decades of European expertise in millimeter astronomy," commented Karl Schuster, director of IRAM and member of the EHT board.
The Horizon Telescope (EHT) event – an assembly of eight ground-based radio telescopes forged through international collaboration – has been designed to capture images of a black hole. At coordinated press conferences around the world, the EHT researchers showed that they were able to reveal the first direct visual evidence of a supermassive black hole and its shadow. This 17-minute film examines the efforts that have led to this historic image, from the science of Einstein and Schwarzschild to the struggles and successes of EHT collaboration. Credit: ESO
The construction of the EHT and the observations announced today constitute the culmination of decades of observational, technical and theoretical work. This example of global teamwork required close collaboration from researchers around the world. Thirteen partner institutions worked together to create the EHT, using both the existing infrastructure and the support of various agencies. The main financial resources were provided by the US National Science Foundation (NSF), the European Research Council of the European Union (ERC) and funding agencies in East Asia.
The Horizon Telescope (EHT) event – an assembly of eight ground-based radio telescopes forged through international collaboration – has been designed to capture images of a black hole. At coordinated press conferences around the world, the EHT researchers showed that they were able to reveal the first direct visual evidence of a supermassive black hole and its shadow.
"ESO is pleased to have contributed significantly to this result through its leadership in Europe and its key role in two of EHT's Chile-based component telescopes, ALMA and APEX," commented Xavier Barcons, Director-General of ESO. "ALMA is the most sensitive device in the EHT and its 66 high-precision antennas have been crucial to the success of the EHT."
In anticipation of the first image of a black hole, Jordy Davelaar and his colleagues built a simulation of the virtual reality of one of these fascinating astrophysical objects. Your simulation shows a black hole surrounded by luminescent material. This matter disappears in a swirl-like manner in the black hole and becomes a glowing plasma due to the extreme conditions. The emitted light is then deflected and deformed by the strong gravity of the black hole.
"We achieved something that was considered impossible a generation ago," Doeleman concluded. "Breakthroughs in technology, connections between the best radio observatories in the world and innovative algorithms have led to a completely new window on black holes and the event horizon."
The impression of this artist shows the black hole in the heart of the huge elliptical galaxy M87. This black hole was selected by the Event Horizon Telescope as an object for paradigm-shifting observations. The overheated material surrounding the black hole is shown.
The impression of this artist shows the black hole in the heart of the huge elliptical galaxy M87. This black hole was selected by the Event Horizon Telescope as an object for paradigm-shifting observations. Shown here is the overheated material that surrounds the black hole, as well as the relativistic jet that is launched from M87's black hole.