Black holes have finally been dragged out of the shadows.
For the first time ever, humanity has photographed one of these elusive cosmic beasts, shining light on an exotic space-time realm that had long been beyond our ken.
"We have seen what we thought was unseeable," Sheperd Doeleman, of Harvard University and the Harvard-Smithsonian Center for Astrophysics, said today (April 10) during a press conference at the National Press Club in Washington, D.C.Doeleman directs the Event Horizon Telescope (EHT) project, which captured the epic imagery. These four photos, which were unveiled today at press events around the world and in a series of papers, outline the contours of the monster black hole lurking at the heart of the elliptical galaxy M87.
The imagery is mind-blowing enough in its own right. But even more significant is the trail the new results will likely blaze, researchers said.
"There's really a new field to explore," Peter Galison, a professor of physics and the history of science at Harvard, said in an EHT talk last month at the South by Southwest (SXSW) festival in Austin, Texas. "And that's ultimately what's so exciting about this."
Galison, who co-founded Harvard's interdisciplinary Black Hole Initiative (BHI), compared the imagery's potential impact to that of the drawings made by English scientist Robert Hooke in the 1600s. These illustrations showed people what insects and plants look like through a microscope.
"It opened a world," Galison said of Hooke's work.
A telescope the size of Earth
The EHT is a consortium of more than 200 scientists that has been in the works for about two decades. It's a truly international endeavor; funding over the years has come from the U.S. National Science Foundation and many other organizations in countries around the world.
The project takes its name from a black hole's famed point of no return - the boundary beyond which nothing, not even light, can escape the object's gravitational clutches.
"The event horizon is the ultimate prison wall," BHI founding director Avi Loeb, the chair of Harvard's astronomy department, told Space.com. (Loeb is not part of the EHT team.) "Once you're in, you can never get out."
It's therefore impossible to photograph the interior of a black hole, unless you somehow manage to get in there yourself. (You and your pictures couldn't make it back to the outside world, of course.) So, the EHT images the event horizon, mapping out the black hole's dark silhouette.
"We're looking for the loss of photons," EHT science council member Dan Marrone, an associate professor of astronomy at the University of Arizona, told Space.com.
The project has been scrutinizing two black holes - the M87 behemoth, which harbors about 6.5 billion times the mass of Earth's sun, and our own Milky Way galaxy's central black hole, known as Sagittarius A*. This latter object, while still a supermassive black hole, is a runt compared to M87's beast, containing a mere 4.3 million solar masses.
Both of these objects are tough targets because of their immense distance from Earth. Sagittarius A* lies about 26,000 light-years from us, and M87's black hole is a whopping 53.5 million light-years away.
From our perspective, Sagittarius A*'s event horizon "is so small that it's the equivalent of seeing an orange on the moon or being able to read the newspaper in Los Angeles while you're sitting in New York City," Doeleman said during the SXSW event last month.
No single telescope on Earth can make that observation, so Doeleman and the rest of the EHT team had to get creative. The researchers have linked up radio telescopes in Arizona, Spain, Mexico, Antarctica and other places around the world, forming a virtual instrument the size of Earth.