Using a global network of telescopes to see “the unseeable,” an international scientific team on Wednesday announced a milestone in astrophysics – the first-ever photo of a black hole – in an achievement that validated a pillar of science put forward by Albert Einstein more than a century ago.
Black holes are monstrous celestial entities exerting gravitational fields so vicious that no matter or light can escape. The photo of the black hole at the centre of Messier 87, or M87, a massive galaxy in the relatively nearby Virgo galaxy cluster, shows a glowing ring of red, yellow and white surrounding a dark centre.
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.
The team’s observations strongly validated the theory of general relativity proposed in 1915 by Einstein, the famed theoretical physicist, to explain the laws of gravity and their relation to other natural forces.
“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.
Doeleman said the research “verifies Einstein’s theory of gravity in this most extreme laboratory.”
Black holes, phenomenally dense celestial entities, are extraordinarily difficult to observe by their very nature despite their great mass. 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.
The black hole observed by the scientific team resides about 54 million light-years from Earth.
A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). This black hole is an almost-unimaginable 6.5 billion times the mass of the Sun.
“This is a huge day in astrophysics,” said US National Science Foundation Director France Córdova. “We’re seeing the unseeable.”
“It did bring tears to my eyes,” Córdova added.
Ring of light
The fact that black holes do not allow light to escape makes viewing them difficult.
The scientists look for a ring of light – hot 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.
The scientists said Einstein’s theory predicted the shape of the shadow would be almost a perfect circle – as it turned out to be.
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,” Psaltis added.
“Science fiction has become science fact,” University of Arizona astronomy professor Daniel Marrone said.
The project’s researchers obtained the first data in April 2017 using radio 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 has essentially created a planet-sized observational dish.
The project also targeted another black hole – Sagittarius A* is situated at the centre of our own Milky Way galaxy – but did not announce any pictures of that one, though scientists expressed optimism about getting such an image.
Sagittarius A* possesses 4 million times the mass of our sun and is located 26,000 light-years from Earth.