The Greenland Telescope at the Thule Air Base.Nimesh Patel/EHT project
In space, black holes are massive objects with gravity so strong that they can bend space and time to the breaking point.
Here on Earth, the prospect of seeing a black hole for the first time is having a similar effect on the media’s ability to contain its enthusiasm for what promises to be one of the biggest science stories of the year.
For several days, the news has been burbling with hints that the first direct image of a black hole will be revealed to the public at parallel news conferences on Wednesday, concurrent with the publication of the image in a peer-reviewed scientific journal.
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The main event is scheduled for 9 a.m. ET in Washington, where scientists leading an international project called the Event Horizon Telescope will release their latest findings.
The telescope is not a single instrument but a collaboration involving radio observatories around the world, including facilities in Hawaii, Chile, Europe and at the South Pole.
When used together to observe the same target, the radio dishes at these widely distributed facilities can lock onto a signal with the same precision as an imaginary receiver as large as Earth.
That’s exactly what is needed to observe a giant black hole in the distant galaxy M87, or at the centre of the Milky Way, the only two places where scientists say the combined size and distance of known black holes puts the prospect of getting an image within reach.
“It’s a special moment,” said Avery Broderick, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ont., who has been with the project for more than a decade and is set to join his colleagues for what is expected to be a historic reveal.
Black holes are regions where mass has been concentrated beyond the point where anything can withstand its gravitational force. Not even light can escape such an object. All matter that falls inside a black hole is crushed to a point at the centre called the singularity, where spacetime folds in on itself. Theory states that the singularity is permanently hidden from view behind the “event horizon,” defined as the radius within which nothing can leave the black hole.
Being black, the event horizon is a challenge to observe. However, a black hole that is located within the crowded centre of a galaxy draws matter toward itself. Before plunging in, that matter forms a glowing whirlpool of hot gas that spins around the invisible source of attraction. The goal of the Event Horizon Telescope team has been to spy the dark edge of a black hole in silhouette against that glowing backdrop of hot gas.
This is a technical feat so demanding – akin to spotting a quarter on the surface of the moon – that the journey to make it possible has pushed technology to its limits. Optical telescopes are not capable of making such an observation, in part because both potential target black holes are embedded within dense thickets of dust and stars that obscure the view.
Radio waves from the hot gas surrounding the black holes are a different matter. Researchers with the Event Horizon Telescope have already confirmed that they can detect these signals. Now the question is whether they can be mapped with enough precision to create a picture – and what that picture will reveal about the extreme environments surrounding black holes, where the more bizarre aspects of Einstein’s theory of general relativity are working at full force.
Beyond the sheer achievement of seeing what a black hole looks like, scientists hope the result will reveal new details about how the universe operates under conditions that are well beyond the reach of laboratory experiments.
“The first direct image of a black hole would be absolutely groundbreaking,” said Meg Urry, an astronomer at Yale University who has spent much of her career studying the indirect effects of the giant black holes thought to reside in the centres of most galaxies.
Dr. Urry pointed out that evidence for the existence of black holes has mounted steadily since the 1960s, including the Nobel Prize-winning detection, in 2015, of vibrations in spacetime from two colliding black holes by the LIGO experiment.
“But still,” she added, “A picture is worth a thousand words.”