An international scientific team has announced a milestone in astrophysics - the first photo of a black hole - using a global network of telescopes to gain insight into celestial objects with gravitational fields so strong no matter or light can escape.
The team's observations of the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster, lend strong support to the theory of general relativity put forward in 1915 by physicist Albert Einstein to explain the laws of gravity and their relation to other natural forces.
The research was conducted by the Event Horizon Telescope (EHT) project, an international collaboration begun in 2012 to try to directly observe the immediate environment of a black hole using a global network of Earth-based telescopes.
The announcement was made in simultaneous news conferences in Washington, Brussels, Santiago, Shanghai, Taipei and Tokyo.
"We have achieved something presumed to be impossible just a generation ago," said astrophysicist Sheperd Doeleman, director of the Event Horizon Telescope at the Center for Astrophysics, Harvard & Smithsonian.
This black hole is found about 54 million light years from Earth.
A light year is the distance light travels in a year: 9.5 trillion km.
Black holes, phenomenally dense celestial entities, are extraordinarily difficult to observe despite their great mass.
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A black hole's event horizon is the point of no return beyond which anything - stars, planets, gas, dust and all forms of electromagnetic radiation - gets swallowed into oblivion.
"This is a huge day in astrophysics," said US National Science Foundation Director France Córdova.
"We're seeing the unseeable."
The fact that black holes do not allow light to escape makes viewing them difficult.
The scientists look for a ring of light - disrupted matter and radiation circling at tremendous speed at the edge of the event horizon - around a region of darkness representing the actual black hole. This is known as the black hole's shadow or silhouette.
Astrophysicist Dimitrios Psaltis of the University of Arizona, the EHT project scientist, said: "The size and shape of the shadow matches the precise predictions of Einstein’s general theory of relativity, increasing our confidence in this century-old theory."
"Imaging a black hole is just the beginning of our effort to develop new tools that will enable us to interpret the massively complex data that nature gives us," he added.
The project's researchers obtained the first data in April 2017 using telescopes in the US states of Arizona and Hawaii as well as in Mexico, Chile, Spain and Antarctica. Since then, telescopes in France and Greenland have been added to the global network. The global network of telescopes has essentially created a planet-sized observational dish.