Published by the Chandra X-ray Center (CXC) Issue number 14 Chandra News

Astrophysical black holes have the poten-tial to revolutionize classical black hole physics. After all, the only black holes we know, or may ever know, are astrophysical black holes. But how can we make this journey from astrophysics to physics? In fact, it is well underway (e.g., see §8 in Remillard & McClintock 2006), and Chandra is making leading contributions by (1) providing strong evidence for the existence of the event horizon — the defining property of a black hole, and by (2) measuring both the spin and mass of an eclipsing stellar black hole in M33. Meanwhile, Constellation-X promises to deliver the ultimate prize, namely, a quantitative test of the Kerr metric. One of the most remarkable predictions of black hole physics is that two numbers specifying mass and spin suffice to provide a complete and absolutely exact description of the space-time surrounding a stationary rotating black hole. Testing this prediction is the most important contribution that astrophysics can make to black hole physics. Chandra and Constellation-X Home in on the Event Horizon