The biggest problem with trying to detect a black hole is that even the supermassive ones are relatively tiny.
"The largest one in the sky [is] the black hole in the center of the Milky Way," Dimitrios Psaltis, an astrophysicist at the University of Arizona, writes me in an email. "And taking a picture of it would be equivalent to taking a picture of a DVD on the surface of the moon."
What's more, because of their strong gravity, black holes tend to be surrounded by other bright matter that makes it hard to see the object itself.
That's why, when hunting for black holes, astronomers don't usually try for direct observation. Instead, they look for evidence of the effects of a black hole's gravity and radiation.
But an ongoing effort is linking up several radio telescopes around the world in an effort to see a black hole up close for the first time. The historic image is due in 2017.
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