Chandra/Black Black Holes
Credit: CXC/M. Weiss

Black Black Holes

"It is a bit odd to say we've discovered something by seeing almost nothing at all -- less than the smile of the Cheshire cat, so to speak, but, in essence, this is what we have done." said Dr. Michael Garcia of the Harvard-Smithsonian Center for Astrophysics. Dr Garcia was referring to startlingly new evidence of the existence of "event horizons" in the Universe. An "event horizon" is popularly often thought of as the "surface" around a black hole; in reality these "horizons" represent local boundaries in Einstein's spacetime. Objects inside the boundary cannot communicate with objects outside the boundary. Thus things that pass the event horizon (or "fall into a black hole", so to speak) are effectively "lost" to the rest of the Universe. Garcia and his colleagues (Jeffrey McClintock, Ramesh Narayan, and Stephen Murray of the Harvard-Smithsonian Center for Astrophysics and Dr. Paul Callanan of University College, Cork, Ireland) used data obtained by the Chandra and ROSAT X-ray telescopes to probe "X-ray novae" (violently variable stars which sometime erupt in a burst of X radiation). These novae are powered by unstable flows of matter which spiral onto the surface of a neutron star, or into a black hole. The Chandra and ROSAT data showed that, when not experiencing a violent outburst, the X-ray novae which contain black holes were only 1% as bright as the X-ray novae which contain neutron stars. The interpretation of the missing light is that it probably a result of the black hole completely swallowing material (and the radiation it produces) as the material passes the boundary of the event horizon.

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Page Author: Dr. Michael F. Corcoran
Last modified March 19, 2001