If you want to take a picture of a black hole, you need a really powerful telescope. And if you want a really powerful telescope, it needs to be big.
So scientists had an idea: What if astronomers across the planet cooperated, and at the same time, pointed many telescopes all over the globe to one particular spot in space, effectively creating a virtual telescope as big as planet Earth?
In 2019, the Event Horizon Telescope (EHT), a planet-scale array of observatories, announced it did just that. The results were groundbreaking: Astronomers captured the first-ever picture of a black hole, a region of space where gravity is so strong not even light can escape.
Pierre Christian, assistant professor of physics at Fairfield University, said the photograph of a black hole 55 million light-years from Earth with a mass 6.5 billion times that of the sun was just the beginning.
“This is just a starting point,” Christian said. “We are barely skimming the surface of what we can actually learn from these datasets.”
Christian is part of the EHT project, which he began working on as a graduate student.
He said “having a picture of a black hole means you can start testing various theories of gravity. Because different theories of gravity will give different pictures.” And that, he pointed out, is groundbreaking.
Unifying gravity with nature’s other three fundamental forces – electromagnetism and the strong and weak nuclear force – in a so-called “theory of everything” has long eluded scientists.
“Physics basically [has] already understood three of these forces,” Christian said. “Gravity is the last piece of the puzzle. It’s the holy grail of physics.”
Christian and other scientists are now combing through the EHT data, tweaking gravitational variables in computer simulations to see if they can jockey the numbers in a way that would work toward uniting those fundamental forces.
But he said the black hole photographed by the EHT project provides a critical fact check on any theoretical number crunching.
“Whatever theory of gravity that I came up with must create that picture,” Christian said. “Now you have a range of allowed deviation – your new theory of gravity cannot be so different, because if it’s too different, then it’s not going to create that picture.
“We can start figuring out whether our understanding of gravity is right or wrong,” he said. “That’s why it’s important scientifically.”
And he said scientists are now considering ways they can create even bigger virtual telescopes that peer deeper into the mysteries hidden in the inky-black beyond.
“There are now people who [are] thinking about: Why don’t we do this same experiment, putting this telescope – instead of on Earth – why don’t we put them in space?
“You put it in space, you can simulate a much bigger telescope,” Christian said. “We’re just starting. This is a new era of black hole research.”