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The Strongest Gravitational Fields Ever Observed

X rays (green cone) are emitted when gas from a blob orbiting a neutron star (red sphere) takes a final plunge onto the star's surface. The gas, originating in a nearby conventional star (not shown), is drawn toward the neutron star and accumulates in an accretion disk (shaded blue). The Rossi X-Ray Timing Explorer (RXTE) satellite is able to monitor x rays from such binary star systems over very microsecond time periods. Quasi-periodic oscillations (QPOs) in the x-ray brightness of the star are thought to arise when the stream of gas being fed onto the neutron star (and the corresponding x-ray generating "hot spot" where the gas makes contact with the surface) moves around behind the star. (Courtesy of Frederick Lamb, University of Illinois at Urbana-Champaign.)

This research was reported at the 1998 Joint Meeting of the American Physical Society and American Association of Physics Teachers in Columbus, Ohio.