It’s common for galaxies to have black holes at their center. In fact, our own galaxy has a pretty big one at the center. But nothing will quite prepare you for the size of NGC 4889, a galaxy with a black hole at the center nearly the size of our solar system.
Recently photographed by the Hubble, NGC 4889 is home to a black hole 21 billion times the mass of the sun. No, that’s not a typo; by contrast, the Milky Way’s black hole is a relatively dinky 4 million times the mass of the sun. NGC 4889 is so dense that its event horizon, the point where even light can’t escape, is about 130 billion kilometers in diameter, or fifteen times as big as Neptune’s orbit around the sun.
If you’re wondering why there’s even a galaxy there, the short answer is that this particular black hole has overeaten and is taking a nap. It’s consumed so much mass that it’s considered satiated at this point, and in fact the remaining detritus around it is forming into stars, not unlike the theory that a black hole could serve as a “sun” to a planetary system. It’s currently unlikely to start sucking up matter again, which is good, because it’s only about 300 million light years away, and black holes can book it when they want to. That said, all it takes is a star blundering in to wake it up, so if it starts heading for us, let’s just hope the theory that we won’t notice being sucked in holds true.
(Via the European Space Agency and Yahoo!)