PKS 2155-304 (Credit: figure and text from EXOSAT slide set) The hard X-ray light curve of the BL Lac object PKS 2155-304, seen with the medium energy detectors on board EXOSAT. The variability is so rapid (a factor of 10 in 6 hours) and the luminosity so high that relativistic bulk motions, nearly along the line of sight, are probably occurring. This is direct evidence of relativistic beaming. Search for an Image: (Enter the name of an object.) Additions or Comments: Have we left anything out? Is there something you would like to have added to this page (a link to your own group's research page, for example...)? IMAGES | By Mission | Stars | Cataclysmic Variables | X-ray Binaries | Pulsars | Supernova Remnants & Planetary Nebulae | Galaxies | Active Galactic Nuclei | Clusters and Groups of Galaxies | X-ray/gamma-ray Background & Deep Fields | Solar System Objects | Gamma Ray Bursts HEASARC Home | Observatories | Archive | Calibration | Software | Tools | Students/Teachers/Public Last modified: Thursday, 26-Jun-2003 13:48:46 EDT