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, until now, been an object of mystery.
Katie Bouman, of the Massachusetts Institute of Technology, led the creation of the Event Horizon Telescope (EHT) project. These photos, which were unveiled today at press events around the world and in a series of published 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.
The EHT is a squad of more than 200 scientists, and 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 event horizon, which is the boundary beyond which nothing, not even light, can escape the object's gravitational clutches. It's therefore impossible to photograph the interior of a black hole, unless you somehow manage to get in there yourself (but 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. 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," Bouman said during the SXSW event last month.
No single telescope on Earth can make that observation, so Bouman 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.
The EHT project has two main goals: to image an event horizon for the first time ever, and to help determine if Einstein's theory of general relativity needs any revisions.
Before Einstein came along, gravity was generally regarded as a mysterious force at a distance. But general relativity describes it as the warping of space-time: Massive objects such as planets, stars and black holes create a sort of sag in space-time, much as a bowling ball would if placed on a trampoline. Nearby objects follow this curve and get funneled toward the central mass.
General relativity has held up incredibly well over the century since its introduction, passing every test that scientists have thrown at it. But the EHT's observations provide another trial, in an extreme realm where predictions may not match reality. That's because astronomers can calculate the expected size and shape of an event horizon using general relativity. If the observed silhouette matches the theory-informed simulations, then Einstein was 100% right. If the answer is no, then we have to tweak his theory in order to make it work with experiments. This is how science goes.
And we learned today that no tweaks are needed, at least at the moment; EHT's M87 observations are consistent with general relativity, team members said. Namely, the event horizon is nearly circular and is the "right" size for a black hole of that immense mass.
Then there's the broader appeal of the newly released imagery - how it speaks to those of us who aren't astrophysicists. The contributions in this arena could be significant. Photos can change the way we think about ourselves and our place in the universe. This image, which gave the masses a glimpse of our planet as it really is - a lonely outpost of life in an infinite sea of darkness - is widely credited with helping to spur the environmental movement.
Seeing a real-life black hole - or its silhouette, anyway - "is the stuff of science fiction.” And this is just the first photo. In 1996, the only pictures we had of Pluto looked like what you see on the left. If it took only 20 years to advance the photo quality to the picture on the right, just imagine the black hole images we’ll be looking at in 2040.
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Source: This story was originally published on Space.com. We are republishing a lightly edited version to SkyFeed in light of interest on the subject. Wall, Mike. "Eureka! Black Hole Photographed for 1st Time." Space.com. 10 April 2019. Web article.
Citation: Rovira, Lia N. "Astronomers Capture the First-Ever Image of a Black Hole!" SkyFeed. 10 April 2019. Web article.