For the first time astronomers have measured the velocity of matter in gamma ray bursts.  They say it is moving at 99.9997% of the speed of light, 299,792 kilometers per second, 186,282 miles per second, or a Lorentz factor of 400.

EurekAlert reports astronomers at the ESO La Silla Observatory lead by Emilio Molinari used data from two gamma ray bursts that occurred on April 18 and June 7, 2006 to make this discovery.  These data included rare data about the peaks of the events which was successfully captured by the 0.6 meter REM telescope at ESO La Silla.  It was the peak data that was crucial to directly measuring the velocity, but that data is rarely captured since it occurs so soon after the initial gamma rays are received.  However, the small size of the REM telescope allowed it to slew very quickly to the correct position once the Swift satellite detected the gamma ray bursts (39 and 41 seconds respectively).

Although single particles can be accelerated considerably faster than this, these events accelerated around 200 times the mass of Earth to this incredible speed.  To give you an idea of the power of a gamma ray burst each one, for a brief moment, is almost as luminous as the rest of the Universe.