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Few things are as fascinating to astronomers or the general public as black holes. Can you imagine something so dense that light cannot escape from it? That sucks in everything that comes its way? If the earth were as compact as a black hole, it would be a ball about a half-inch across! Few things in the universe completely boggle the human mind as black holes.

Black holes were first proposed as theoretical objects in the 18th century, but it was only after Einstein’s General Theory of Relativity was proposed in 1916 that the existence of this kind of object became more probable. One of the key theoreticians was the Indian scientist Subrahmanyan Chandrasekhar who proposed the exact mass needed for a collapsing star to become a “black hole.” The name itself was coined by an American in the late 1960s. In the 1970s, the first indirect evidence for black holes actually existing was generally accepted.

So imagine the surprise of astronomers when these images made by NASA’s Chandra X-ray orbiting observatory (named after S. Chandrasekhar) were recently made available. It shows not one but two black holes orbiting each other! We have known for some time that massive black holes inhabit the center of galaxies, including our own. But two black holes going round and round? This seems to be exactly what is happening some 300 million light years away (that is about 1,781,250,000,000,000,000,000,000 or 1.781 quintillion miles). Whew, thankfully this is nowhere near earth!

The two black holes, white dots in these images, are some 25,000 light years apart. As these gravitational monsters circle each other, they heat the swirling gases around them to millions of degrees, creating the blue X-ray light seen in the image. They are said to be traveling at 750 miles per second (or 2.7 million miles per hour) through this gas! Some of the gas is falling into the black holes, while some of it is being blown away. The pink antennae are radio waves generated by this extraordinary cosmic interaction.

How did the two black holes meet? They are the centers of two colliding galaxies in the Abel galactic cluster. Don’t worry, though– when two galaxies collide, it usually does not mean that their stars collide. The distances between them far are too vast. Instead, gravity bends and distorts the galaxies, sometimes ejecting stars and star clusters from the galaxies. Over time the galactic cores do come together as they are in this case. Will the two black holes finally merge? Astronomers think so. When that happens, this should result in a gamma ray burst, an intense burst of energy that for a few moments can equal the entire amount of energy being released in the rest of the universe. But that, as they say is another story. Solving one mystery in the universe only seems to lead to another!