Getting an image of a black hole is one of those things that seem impossibly challenging, but with the efforts of astronomers all around the world, humanity is finally getting a direct glimpse of this cosmic object.
With the Event Horizon Telescope, scientists capture a supermassive black hole in a historic photograph. More than 200 researchers were involved in the accomplishment.
Since it's an ultra-dense object from which no light can escape, black holes can't actually be seen, much less captured on camera.
So how did scientists manage to achieve this incredible feat? In a series of papers in The Astrophysical Journal Letters, the international team explains how.
Network Of Telescopes Work In Tandem To Capture Black Hole's Shadow
Black holes may be more or less invisible, but they can be spotted by a distinct disk of hot material shining around it brightly.
"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," Heino Falcke, the chair of the EHT Science Council of Radboud University, explains in a statement from EHT. "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 allowed us to measure the enormous mass of M87's black hole."
Scientists used the EHT, an international network of radio telescopes, to hone in on the supermassive black hole that's about 6.5 billion times the mass of the sun.
It is located about 55 million light-years away from Earth in the center of elliptical galaxy Messier 87.
According to NASA, eight ground-based radio telescopes all over the world worked in tandem to capture the shadow of this black hole. These telescopes operated as if they were one giant instrument that's the size of Earth.
With a technique known as very-long-baseline interferometry, the astronomers used the telescopes and the rotation of the planet to form a massive telescope powerful enough to read a newspaper in New York from the opposite end of the world in Paris.
A number of NASA spacecraft also contributed to the efforts, collecting data on the black hole with different wavelengths of light. NASA's Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array, and Neil Gehrels Swift Observatory space telescope missions all participated as well as NASA's Fermi Gamma-ray Space Telescope.
"Years ago, we thought we would have to build a very large space telescope to image a black hole," Paul Hertz, director of the astrophysics division at NASA Headquarters, says. "By getting radio telescopes around the world to work in concert like one instrument, the EHT team achieved this, decades ahead of time."
The Significance Of A Photo
More than just historical value, the photo of the black hole is an important step forward in continuing to study space. It confirms the existence and properties of black holes, which until now, have been entirely based on indirect observations.
All the data, technology, and coordinated efforts involved in capturing the image of this supermassive black hole may answer many of the mysteries that scientists still have not solved about black holes.
In a report from The Harvard Gazette, EHT Director Sheperd Doeleman points out that the event opens up an entirely new door to scientists.
"We are now entering the era of precision, horizon-scale observations of black holes," Doeleman explains. "We've never had that before, so we're now able to ask a bunch of questions we couldn't even conceive of before. We can start teasing apart physical processes at the black hole boundary, so [the significance] is in what we saw, but also in the promise this holds for the future."