‘We’re seeing the unseeable’: Scientists reveal first true image of a black hole
- Astronomers hold six press conferences simultaneously in Belgium, Chile, Shanghai, Japan, Taipei, and the US to unveil results from the Event Horizon Telescope
- Black holes are so powerful that nothing nearby – not even light – can escape their gravitational pull
An international scientific team has unveiled a landmark achievement in astrophysics: the first true image of a black hole.
The image reveals the black hole at the centre of Messier 87 (M87), a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides about 54 million light years from Earth.
Black holes are phenomenally dense celestial entities with gravitational fields so powerful no matter or light can escape, making them extraordinarily difficult to observe despite their great mass.
News conferences took place in Washington, Brussels, Santiago, Shanghai, Taipei and Tokyo to disclose the “groundbreaking result” from the Event Horizon Telescope (EHT) project, begun in 2012 to directly observe the immediate environment of a black hole using a global network of telescopes. The 10 radio telescopes on four continents collectively operate like a single instrument nearly the size of Earth.
“This is a huge day in astrophysics,” said US National Science Foundation Director France Córdova in Washington. “We’re seeing the unseeable.”
Dr Lu Rusen, an astronomer at Shanghai Astronomical Observatory, Chinese Academy of Sciences, who took part in the EHT project, said the contrast ratio between the shadow area of the black hole and surrounding area had reached 1:10, which meant that what they captured was indeed a black hole.
“Einstein was right,” he said at a news conference in Shanghai Wednesday night, paying tribute to the legendary physicist whose theory of general relativity predicted the existence of the black hole.
“The successful imaging of the black hole in the centre of M87 is just the beginning of the EHT collaboration,” said Shen Zhiqiang, director of the Shanghai observatory, who also took part in the project.
China’s astronomers helped capture photo of black hole but couldn’t use world’s biggest telescope to do it
“More exciting results are expected from the EHT project in the near future,” he said. A total of 16 Chinese astronomers took part in the project.
Shen said they would try to use some Chinese telescopes to observe black holes, including the M87 in the future, with some work already started earlier this year.
The EHT project targeted two supermassive black holes residing at the centre of different galaxies. One of the black holes – Sagittarius A* – is situated at the centre of our own Milky Way galaxy, possessing 4 million times the mass of our sun and located 26,000 light years from Earth.
A light year is the distance light travels in a year, 9.5 trillion km (5.9 trillion miles).
The second one – the M87 – inhabits the centre of the neighbouring Virgo A galaxy, boasting a mass 3.5 billion times that of the sun.
At the news conference in Taipei, experts at Taiwan’s top research institute said that the island's scientists had played an important role in proposing, researching and observing the M87 black hole.
Masanori Nakamura of Taiwan’s Academia Sinica said that their research showed that no matter how the gas rotates, whether clockwise or counterclockwise, the lower part of the black hole is always bright and the upper part dim. The research also confirmed that there is a rotating super black hole in M87.
A group of Academia Sinica-led researchers conducted a year-long observation in Hawaii and collected data about the M87 black hole in 2017, the Taiwan researchers said. After that, the researchers started to work on assembling an image of the black hole.
Four teams performed three separate observations, each across a span of seven days, in April last year. They concluded that the images were the same, that the M87 black hole was structured like an eclipsed moon and that its centre was dark.
Black holes, which come in different sizes, are formed when very massive stars collapse at the end of their life cycle.
Supermassive black holes are the largest kind, growing in mass as they devour matter and radiation and perhaps merging with other black holes.
The fact that black holes do not allow light to escape makes viewing them difficult.
Albert Einstein’s theories posited the existence of black holes. Although scientists have obtained much indirect evidence that suggested the existence of such celestial bodies, no one has seen one.
The term itself was coined by American physicist John Archibald Wheeler in the mid-1960s.
The project’s researchers obtained the first data in April 2017 using telescopes in the US states of Arizona and Hawaii as well as Mexico, Chile, Spain and Antarctica. Chinese scientists also took part in the observations in Spain and Hawaii.
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.
Professor Wu Xuebing, director of the department of astronomy in the school of physics at Peking University in Beijing, had said earlier that researchers in China made “important contributions” to the creation of the black hole photo.
They included computer modelling and data analysis. The observations by the EHT arrays lasted only a few hours, but it took researchers nearly a year to merge the fragmented images into a complete picture.
“The amount of data processed is enormous,” Wu said. “It is an achievement not possible for any single country, but took global collaboration.”
The project was supported by the Chinese Academy of Sciences’ Centre for Astronomical Mega-Science, co-established by the National Astronomical Observatories of China, Purple Mountain Observatory, in Nanjing, Jiangsu province, and Shanghai Astronomical Observatory.
The ultimate goal of imaging black holes is “to understand the formation of the universe”, said Anton Zensus, director of Germany’s Max Planck Institute for Radio Astronomy.
Yau Shing-Tung, a senior faculty member of Harvard’s Black Hole Initiative, said: “A direct observation of black holes will be tremendous for our understanding of the space-time that we are in.”
Agence France-Presse, Reuters, Xinhua and Lawrence Chung