Beautiful golden ring revealed as humanity’s first glimpse of a black hole

10 Apr 2019

An artist’s impression of the enormous elliptical galaxy M87. Image: ESO/M Kornmesser

After much anticipation, ESO researchers finally revealed humanity’s first ever glimpse of a black hole.

Decades of effort to simply see one of the most perplexing phenomena in the known universe have finally come to fruition. As part of a global announcement, the European Southern Observatory (ESO) and the Event Horizon Telescope (EHT) unveiled the first ever photo of a black hole’s event horizon, the centre point of a black hole where unquantifiable amounts of mass are shrunk down to a zero-dimensional point in space.

There was little doubt as to the news behind the cryptic announcement, with the EHT’s purpose being solely to capture an image of a black hole.

The international collaboration set out to link radio dishes across the world to create an Earth-sized interferometer, rather than trying to build a single, impossibly large dish.

So far, the network of eight dishes has focused its attention on the two supermassive black holes with the largest apparent event horizons: Sagittarius A* at the centre of the Milky Way and M87 in the centre of the Virgo A galaxy.

Prior to the announcement, Prof Peter Gallagher of the Dublin Institute for Advanced Studies (DIAS) was most interested in seeing how the image would appear. If it were to appear as a circle of bright matter – known as an accretion disc – then that would be interesting in itself.

A golden ring surrounding the black hole event horizon.

The first image of a black hole capture by the EHT. Image: EHT Collaboration

‘Reveals a lot about these fascinating objects’

But researchers wondered whether the appearance of a different shape meant Einstein’s theory of general relativity “wasn’t all it was cracked up to be”, to put it lightly.

As it turned out, Einstein would have heaved a sigh of relief as ESO revealed the stunning, doughnut-shaped image of the black hole.

In a series of six papers published to The Astrophysical Journal Letters, the researchers showed the black hole found at the centre of M87. The numbers involved in this discovery are mind-boggling, with it residing 55m light years from Earth and having a mass 6.5bn times that of our sun.

“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 chair of the EHT Science Council, Heino Falcke of Radboud University in 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 has allowed us to measure the enormous mass of M87’s black hole.”

‘A dramatic moment for a theorist’

The breakthrough was achieved thanks to a technique called very long baseline interferometry (VLBI), which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3mm. Drawing an analogy, ESO said this is the equivalent of being able to read a newspaper in New York from a café in Paris.

Speaking of how it confirms previously held theories established in science, EHT board member Luciano Rezzolla of Goethe Universität in Germany admitted that it was a relief to see they all held up with this image.

“The confrontation of theory with observations is always a dramatic moment for a theorist. It was a relief and a source of pride to realise that the observations matched our predictions so well,” he said.

It now seems a certainty that the team behind this discovery will be strong favourites for a Nobel Prize in Physics given the importance of this image in the fields of astronomy and astrophysics.

Colm Gorey was a senior journalist with Silicon Republic