This is cool
5/18-NASA/Space Science News home
Observation details and announcements from the University of Amsterdam,
Danish 1.54-meter La Silla telescope, the Astronomical Observatory of
Brera, and the University of Warsaw 1.3-meter telescope, and the South
African Astronomical Observatory.The Australian National University's
1.3-meter Mount Stromlo telescope was first to spot the counterpart, but
was delayed in reporting it.
The first on record was P.M. Vreeswijk of the University of Amsterdam
using the 1-meter Swope telescope at the European Southern Observatory,
in the Chilean Andes just 9 hours after the burst was noted by BATSE.
Vreeswijk is a member of the science team, led by Jan van Paradijs, that
found the first GRB optical counterpart in February 1997. Van Paradijs
works at the University of Alabama in Huntsville.
In quick succession, sightings were reported by ANTU, one of the
8.2-meter Very Large Telescopes at ESO's Paranal Observatory - which
just recently had "first light" - and the 1.3-meter Warsaw telescope in
Las Campanas, Chile, operated by Poland, and by the 1-meter South
African Astronomical Observatory telescope at Sutherland, South Africa.
With those observations, astronomers now report a redshift of z=1.619,
putting the burst source about 10 billion light years away. Astronomers
are now trying to determine if it is associated with a galaxy that can't
be seen until the burst fades away.
The redshift is a measure of how far known spectral lines are shifted
due to the expansion of the Universe. Astronomer Edwin Hubble noted
early on in this century that objects in deep space appear to be moving
away from our own Milky Way, and the farther away, the faster they
appear to be moving.
It is this apparent motion that causes the shift in the spectral lines.
Scientists now know that this is apparent velocity is not actually
caused by distant galaxies moving through space, but instead we are
observing the actual expansion of the Universe and everything in it. A
redshift of 1.6 means the expansion of the universe has caused lines in
the object's spectrum to be shifted by a factor of 2.6 in wavelength
(1+z).
The total energy from the burst is estimated at 1.6x1053 ergs (that's 16
followed by 52 zeroes), equivalent to our sun's output for 1.3 trillion
years - about 88 times the current age of the universe.
The ANTU VLT team also reports detecting slight polarization of the light, indicating that at least part of the light is emitted by electrons spiraling along strong magnetic field lines. As observed by BATSE, GRB990510 looks like two bursts with an initial burst lasting about 10 seconds, followed by a 30-second gap, and then another burst that trails off gradually until it makes a final hiccup about 90 second after the first flash of gamma rays.