Prof. Jan van Paradijs is the seventh lecturer to come to Clemson
University. He is known internationally for his discoveries in
X-ray astronomy and most recently for the optical emission from
cosmic gamma-ray bursts.
He is a member of the Astronomical Institute of the University of
Amsterdam. He is also the Pei-Ling Chan Eminent Scholar of Physics
in the Physics Department of the University of Alabama, Huntsville.
Most recently he was awarded the Bruno Rossi Prize of the American
Astronomical Society Division of High Energy Astrophysics.
COSMIC GAMMA-RAY BURSTS
Discovered in the late sixties by American satellites monitoring the
US-USSR nuclear test ban treaty, the phenomenon of cosmic gamma-ray
bursts still defies explanation. Until recently, astronomers did not
even know their distance scale, but now we know that gamma-ray bursts
occur at cosmological distances, past those of quasars, and perhaps
providing clues to star formation commencing shortly after the birth
of the universe. We observe these explosions about once per day as a
flash of very energetic photon radiation (gamma-rays), lasting only
for seconds and apparently not repeating. To catch a burst, one monitors
the whole sky at all times, because their positions are unpredictable.
Fortunately they are bright, and in fact outshine every source on the
sky - while they last. We must extract information during the precious
few seconds they are visible. This requires satellites, because
gamma-rays do not reach the Earth's surface. The Compton Gamma Ray
Observatory, launched by NASA in 1991, has significantly advanced our
understanding of bursts, and the Dutch-Italian X-ray satellite
Beppo SAX, launched in 1996, brought us X-ray afterglows and
in turn optical afterglows. These observations led to the discoveries
of quiescent counterparts (host galaxies) and thus established the
cosmic distant scale.
Main Page
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Prof. Jan van Paradijs in Clemson Astrophysics
library, November 1998.
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