On April 10, humanity achieved a truly remarkable feat. We were able to reach across 55 million light years of space and capture a photo of a black hole for the very first time, after decades of theorising and calculating what it would look like.
The image was captured by the Event Horizon Telescope, a joint mission by astronomers from various countries, peeking at the supermassive black hole in the galaxy M87, one that's 6.5 billion times larger than our Sun.
EHT
The reason this is so spectacular an achievement isn't just because of the distance involved however. You see, black holes are generally invisible thanks to their intense gravitational field. So what the scientists have done is capture the energy at the event horizon, the border just beyond which all of it is swallowed up.
"We are giving humanity its first view of a black hole - a one-way door out of our universe," says Sheperd Doeleman of the Haystack Observatory at the Massachusetts Institute of Technology (MIT), also the lead astronomer at EHT. "This is a landmark in astronomy, an unprecedented scientific feat accomplished by a team of more than 200 researchers."
To observe the black hole's center, astronomers needed a telescope with an angular resolution similar to that of the event horizon. That means they needed a camera with a resolution so high it could spot an orange on the surface of the Moon from Earth. Such a camera would have to have a reflector dish as large as our planet. And though that may be possible in science fiction, we're incapable of building anything of its kind right now.
Instead, the EHT researchers used a technique called very-long-baseline interferometry (VLBI). It involves detecting radio signals from an astronomical source using a network of different radio telescopes. As such, the EHT was formed by combining the capabilities of eight radio telescopes from observatories in six locations around the world, including the Atacama Large Millimeter Array (ALMA) in Chile, South Pole Telescope (SPT) in Antarctica, and the IRAM 30-metre telescope in Spain.?
Each telescope's readings are tagged with precise time stamps using an atomic clock at the location. They each produced about 350TB of data each day that were stored on high-performance helium-filled hard drives. The scientists then later compiled all the data together, using supercomputers at the Max Planck Institute for Radio Astronomy in Germany and the MIT Haystack Observatory in the US, to resolve the final image.?
Until now, the event horizon has simply been a mathematical concept, with its depiction in the movie Interstellar the closest to reality. Now, we can actually see the event horizon for ourselves as a physical phenomenon.
EHT
In fact in future, scientists at EHT hope to add more telescopes to the array, therefore improving its resolution. Maybe that way we'll one day soon get an up close and personal look at one of the most terrifying things in deep space.