Scientists Catch a Black Hole Red-Handed

By Jeffrey Kluger

Astronomers looking for black holes have long known that the deck is stacked against them. In order to find a heavenly body, sky gazers ordinarily take a straightforward approach, hoping simply to eyeball the object through a telescope. But black holes, which are formed by collapsed stars or compressed matter at the center of galaxies, are so dense that nothing--not even light--can escape their gravity. Last week, however, investigators at NASA's Goddard Space Flight Center in Greenbelt, Md., announced that they had at last seen direct evidence of a black hole in action.

Until now, the best clues to the existence of a black hole were X-ray emissions from its accretion disk, the swirl of nearby matter that is steadily being pulled into the body. When the Goddard scientists looked at a suspected black hole in a galaxy 100 million light-years away, however, they saw X rays not being emitted but being absorbed--the signature of ionized iron gas being drawn directly into the maw of the hole. The scientists knew the gas was on the move because its X rays were redshifted, stretched as their speed increased so that they moved toward the red end of the electromagnetic spectrum.

What impressed the research team was not just the fact that the gas was moving but how fast it was moving--6.5 million m.p.h., judging by the redshift. This is exactly the kind of searing speed a black hole ought to produce. While the Goddard scientists may not have the distinction of being the first to see a black hole itself, they are thus the first direct witnesses of its extraordinary power.

--By Jeffrey Kluger