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If it looks like a black hole, and acts like a black hole, it's probably a black hole.For a while now scientists have thought a dense, massive object lurking at the center of our galaxy is likely a giant black hole, but they haven't been able to prove it.New observations offering the closest view yet of the heart of the Milky Way present strong evidence for the black hole theory, and even hope of finally settling the question soon.By linking a series of radio telescopes around the world, astronomers created a virtual telescope with the resolving power of a single dish the size of the distance between the various sites (about 2,800 miles, or 4,500 kilometers).This instrument grabbed an intimate image that probed nearly to the Milky Way's black hole's event horizon — the point beyond which nothing, including light, could ever escape.Blessing and a curse
Since our own galaxy's apparent supermassive black hole is the closest of its kind to us, it offers a unique chance to study how these objects behave and affect galaxies."This is the best black hole candidate that we have anywhere in the universe, the best chance we have to observe the kind of signatures we would expect around the immediate vicinity of a black hole," said study leader Sheperd Doeleman of MIT. "One of the problems with looking at this particular source is that we have to look through our galaxy. It's a blessing that it's this close, but it's a curse because it's obscured by gas and dust."In order to bypass the Milky Way's shroud of gas and dust, the researchers looked at 1.3 mm radio light, which escapes the fog better than longer-wavelength light.They combined observations taken from observatories in Hawaii, Arizona and California in a technique called Very Long Baseline Interferometry (VLBI) to observe the galactic center with some of the highest resolution ever achieved in astronomy — the equivalent of a baseball seen on the surface of the moon, 240,000 miles away.The researchers observed a bright source of light known as Sagittarius A* ("A-star"), thought to mark a black hole roughly 4 million times the mass of the sun.The mass is determined by looking at the effect of the colossal object on stars that orbit near to the galactic center.The team found that Sagittarius A* has a diameter equal to about one-third the distance between Earth and the sun, or about 30 million miles (50 million km).This small size indicates the mass in the galactic center is even denser than previous measurements found, which supports the idea that the object hidden there must be a black hole, because current theories have no other reasonable explanation for describing so much mass packed into such a small space.
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As in the days of Noah...
