The universe's biggest explosions since the Big
Bang
The research conducted by scientists from the
Netherlands, Italy, Denmark, Spain, the UK and Germany confirmed
theoretical predictions that gamma-ray bursts (GRBs) are the most
powerful explosions in the universe, second only to the Big Bang.
They emit high energy radiation and originate in very distant
galaxies, where stars form at a prodigious rate. New clues support
what were once speculations that bursts represented the explosive
death of massive stars. The GRBs may become unique probes of
extreme physics and cosmology, allowing astronomers to trace the
history of star formation in the early cosmos.
Gamma Ray Bursts belong to the most mysterious
phenomena in the Universe, along with the nature of dark matter
and the cosmological constant. The story of their discovery is an
excellent example of a significant progress achieved in scientific
research. The GRBs were first spotted in 1967 by US military
satellites. A systematic search for them began in 1991, when
NASA's Compton Gamma Ray Observatory (CGRO) was launched and began
detecting GRBs at a rate of about one per day. Even then their
origin remained mysterious because gamma ray detectors had very
low positional accuracy and the bursts faded fast.
That changed in 1996 with the launch of the
Italian/Dutch satellite BeppoSAX. Thanks to the unique
multi-faceted capabilities of the satellite, the team of European
scientists solved what has been one of the greatest mysteries of
astrophysics for 30 years - the places of origin of the GRBs. The
BeppoSAX team provided the scientific community with accurate and
rapid locations of GRBs and in 1997 discovered that GRBs keep
glowing in X-rays for several days. Astronomers of the University
of Amsterdam confirmed that the same is true in optical light.
This led to the discovery that the cosmic bursts originate in very
distant galaxies, at the edge of the observable Universe (between
5 and 12 billion light years away, for an assumed age of the
Universe of 13 billion years).
Another breakthrough came in 1998. While Amsterdam
astronomers were observing one of the GRBs they also caught, for
the first time, a stellar explosion simultaneous with the initial
gamma ray burst. This observation provided the researchers with
fresh clues. It was subsequently discovered that a sizeable
fraction of the GRBs is related to very powerful stellar
explosions, so-called "hypernovae", which presumably mark the
final core collapse of very massive stars. The exploding stars are
among the main producers of all elements heavier than helium in
the Universe. These elements enrich the interstellar hydrogen and
helium clouds in the galaxies, which themselves originated in the
Big Bang. Consequently, from the enriched clouds new stars and
planets are formed. The giant stellar explosions that we observe
now as GRBs took place in the early universe. Nonetheless, similar
explosions must have taken place in our own galaxy and long ago
formed the chemical elements which now compose our bodies: carbon,
oxygen, calcium, iron, etc. We, as human beings, would not have
existed without the occurrence of the giant stellar explosions
that we observe as GRBs. The European collaborative nature of the
project was indispensable for all these discoveries. The BeppoSAX
is an Italian/Dutch satellite and the optical follow ups were
performed by astronomers from six different EU countries, using
worldwide observatory networks. The necessary combined expertise
and equipment is not available singularly within Europe and thus
the close co-operation between the international teams was crucial
to the success of the project.
The findings of this scientific research may be
very important cosmic probes of extreme physics and cosmology,
enabling astronomers to trace the history of star formation in the
universe.
Project co-ordinated by Dr.
Edward Van den Heuvel from the University of Amsterdam (the
Netherlands) in co-operation with research teams from the
University of Amsterdam, SRON (the Netherlands), NASA/MSFC (USA),
CNR/IASF in Roma, INAF Trieste and the University of Ferrara
(Italy), the University of Copenhagen (Denmark), LAEFF-INTA
(Spain), Cambridge University (the UK) and Astrophysical Institute
Potsdam (Germany).
Media contacts
- Prof. Edward Van den Heuvel
- University of Amsterdam
Tel:
0031-20 525 7493
E-mail: edvh@science.uva.nl
- Prof. Luigi Piro - CNR/IASF -
Rome
Tel: 0039-06 4993 4007
E-mail: Piro@rm.iasf.cnr.it
- Prof. Jens Hjorth - University
of Copenhagen
Tel: 0045-3532
5928
E-mail: jens@astro.ku.dk
