Perhaps the most celebrated image from space in decades, covered widely by the press for months, was published last year. It was billed as the first ever image of a black hole. Captured 55 million light-years from Earth, in the center of Messier 87 (M87) galaxy, the black hole image offered not only a true glimpse of the cosmic unknown, but helped validate numerous scientific theories — such as further confirming Einstein’s general theory of relativity.
It was a photo with worldwide implications, discussed by scientists and government agencies over the following year — but it wasn’t a photo at all. At least not a photograph, per se. One challenge of studying space is that many celestial objects — and black holes, by definition — are unseeable. The media, to a lesser degree, also mentioned this point in some of its stories last year, noting that the image was generated by collecting data other than light.
But this idea that data can be much more powerful than we might intuitively assume (“we can use new kinds of data to see things we could not see before) is an especially cogent point in today’s data age — an age when the Datasphere itself, the generation of data and the availability of data of all kinds, is expanding at an ever-increasing rate.
Data science and data management enabled this breakthrough, and data is enabling new breakthroughs in many fields every day. Data can allow scientist to “see” what can’t be seen. It’s helping them to drive unprecedented discoveries in vast cosmos — and also here, on Earth. How? A deeper dive into how the black hole image was made provides a prime example.
Data penetrates the celestial veil
Black holes, also known as singularities, are gravitational sinkholes whose force is so powerful that even light cannot escape. (For a sense of that power, consider that our sun, which holds our entire solar system in gravitational orbit, is 6.5 billion times less massive than the M87 black hole). With no light escaping, there’s no picture. Yet, remarkably, data allows us to “see” the M87 black hole. Here’s how: a mountain of data — literally, half a ton worth of hard drives — was collected by radio telescopes, processed by supercomputers with cutting-edge algorithms, and synthesized into a final rendering of an object seated nearly thirty quadrillion miles away.
The effort itself was cosmic in scope.
While black holes aren’t directly visible, the immense fields of superheated gas and cosmic dust pulled into orbit around them, are. This is called an accretion disc, and it forms the bright, halo-like “ring of fire” surrounding the dark shadow, seen in the M87 image. While the shadow is caused by light bending back over the event horizon, the gravitational point of no return, the accretion disk, itself, is extraordinarily bright. It emits high-frequency radio waves, which, though invisible to the human eye, are detectable by radio telescopes, here on Earth.
Enter the Event Horizon Telescope (EHT). The EHT is a planet-wide array of eight synchronized radio telescopes, located everywhere from Arizona, to Spain, to Antarctica. By combining these instruments, the EHT, in effect, creates a telescope dish the size of the Earth itself.
Over seven days in 2017, scientists fixed the EHT’s collective sights on M87. In the process, the telescope compiled an astounding 5 petabytes of light data. To put that in perspective, if a single byte were a 2-by-2-foot tile laid on the ground, a single petabyte would cover the entire Earth. The five petabytes of EHT data was so massive that it could not be transmitted over the internet. Instead, hundreds of physical hard drives — weighing a half ton — had to be flown by airplane to supercomputing centers in Massachusetts and Germany.
Shining light into a black hole
Moreover, rendering the image of the M87 black hole was more complicated than simply uploading the data. Though the size of Earth, the EHT can collect only a tiny fraction of the light emitted by the black hole, from light-years away. This meant that the scientists’ data set was mostly incomplete, like a jigsaw puzzle with nearly all of the pieces missing. This made it hard to construct an accurate image — scientists didn’t even know what the end result was supposed to look like.
“Since we have such sparse measurements, there tends to be an infinite number of images that could match the data,” Lindy Blackburn, a researcher at the Center for Astrophysics in Cambridge, Mass., who worked on the EHT project, told FiveThirtyEight.
Data analysis, however, allowed scientists to hone in on an accurate depiction. To tackle the challenge, four teams of independent scientists each developed entirely new, cutting-edge algorithms that could synthesize the massive data cache into a final image — ruling out results the that were physically implausible, and favoring those that offered simple, and therefore more likely, interpretations.
In the end, the algorithms produced similar, but slightly different results, reports FiveThirtyEight. This is why the final M87 image appears blurry: scientists were conservative about including more granular detail, because even with supercomputing power on their side, uncertainties about the true likeness of the black hole remained.
But astoundingly, to scientists, the final M87 shot looked remarkably familiar. “As far as I’m concerned, the most surprising thing about this image is that it’s not very surprising,” says Avi Loeb, Ph.D., and the founding director of Harvard’s Black Hole Initiative.
While Loeb did not work on the EHT project, in 2009, he devised computer models to predict what M87 might look like. Those predictions, while sharper in resolution, matched the final M87 image almost perfectly.
Data and its vast reaches
The power of data is that is allows scientists to not only predict discoveries in outer space, but to confirm those discoveries with data analysis tools in their own labs. The image of the M87 black hole offered a dramatic example of this otherworldly power in action, one that left the world starstruck. But data is also helping scientists solve other critical mysteries in space — like spotting asteroids on a possible collision course with Earth, or honing in the universe’s “most luminous explosions,” or scouring solar systems to find exoplanets that may harbor conditions for life, similar to those on our home planet.
And these data-driven technologies have other implications here on Earth. The imaging technology that helped scientists “see” the M87 black hole could have future applications for things like MRI diagnostic scans, and even self-driving cars. When scientists use data to drive cosmic discoveries, their tools often proliferate through human communities. And technology from NASA’s Webb Telescope, the successor to the famed Hubble Space Telescope and soon-to-be flagship of celestial inquiry, is being used by doctors to improve patients’ eyesight.
Most things in space are really far away. By helping us peer further into the cosmos, data is bringing breakthrough discoveries back down to Earth — and, in turn, helping scientists use data to build a better world.