Perhaps the only thing weirder than a black hole is a spinning black hole (see Discover, July 2002, page 32), yet astronomers are quickly stripping the mystery from these objects. In the latest twist, a team led by Jane Turner of NASA's Goddard Space Flight Center has found new evidence that light escaping from the edge of a black hole loses energy while climbing the gravitational well created by the black hole's spin, as predicted by Einstein's general theory of relativity.

What a black hole looks like, maybe. Photograph courtesy of NASA/GSFC.

The astronomers used the orbiting Chandra and XMM-Newton X-ray observatories to detect spikes of radiation emitted by energetic iron atoms near the event horizon, the point beyond which nothing can escape a black hole's grip. The spikes originate from hot spots in a luminous disk of gas around a monster black hole—as massive as 20 million suns—in the center of the galaxy NGC 3516. These X-ray observations will allow astronomers to measure whether the hole is indeed spinning and dragging space-time with it. That information, says Turner, will help astronomers attain a better understanding of how relativity influences matter and space under extreme conditions.