Astronomers unravel mystery of gamma ray bursts
|MISSION POSSIBLE: Scientists from the Department of Physics and Astronomy contributed to the development of the X-ray Multi-Mirror [XMM]-Newton telescope, the biggest and most sensitive X-ray telescope ever to be placed in to orbit, which is able to study extremely faint X-ray sources from stars and galaxies in the most distant parts of the Universe|
cause of gamma ray bursts, the most violent and explosive events in the
Universe, has remained a mystery since they were first discovered in 1967. Now a
team of scientists, led by astronomers from the University of Leicester,
believes they have found an answer to the puzzle. Their research results
[published in Nature on 4th April] indicate that gamma ray bursts are
caused by the death of a star so huge that when it dies in a supernova, its core
collapses to form a black hole, resulting in an intense outburst of gamma rays.
Julian Osborne of the University of Leicester explained: “Until now it was
unclear whether gamma ray bursts were caused by a supernova explosion of a giant
star collapsing into a black hole, or by the coalescence of two neutron stars.
Each event could result in an intense outburst of gamma rays, followed by
an X-ray afterglow. By analysing this X-ray afterglow we believe we have
determined the gamma ray burst origin.”
scientists used the EPIC (European Photon Imaging Camera) instrument on the
European Space Agency's [ESA] XMM-Newton space telescope to capture the X-ray
afterglow of a recent gamma ray explosion in a galaxy 10 billion light years
from Earth, and then conducted a detailed spectral analysis of the data. The
results were a great surprise.
James Reeves of the University of Leicester added: “For the first time ever
traces of light chemical elements were detected - including magnesium, silicon,
sulphur, argon, and calcium - neutron star collisions are not expected to make
these. Also, the hot cloud containing these elements is moving towards us at one
tenth of the speed of light. This suggests that the gamma ray burst resulted
from the collapse of the core of a giant star following a supernova explosion.
This is the only way the light elements seen by XMM-Newton, speeding away from
the core, could be produced. So the source of the gamma ray burst is a supernova
and not a neutron star collision.”
added: “The confirmation by XMM-Newton that gamma ray bursts are associated
with supernovae therefore brings scientists closer to understanding the process
that leads to the burst itself.”
UK has taken a leading role in XMM-Newton, as Professor Ian Halliday, Chief
Executive of the Particle Physics and Astronomy Research Council explains:
“From the development of the XMM-Newton concept, the UK has been taking a
strong role, with the University of Leicester leading the way on the EPIC
instrument and on the Survey Science Centre consortium which processes all the
The Mullard Space Science Laboratory built the Optical Monitor telescope
on XMM-Newton, which also captured the fading optical signature of the gamma ray
Ian Halliday, adds: “These latest findings will be tested by SWIFT; a NASA led
space mission that scientists from the University of Leicester and Mullard Space
Science Laboratory are helping to build.
Once it is launched in autumn next year , SWIFT will study over
1000 gamma ray bursts, spotting them rapidly then automatically turning two much
more sensitive telescopes to study these events.
This means that the resulting X-rays can be studied mere seconds after
the event, instead of the hours presently required to manoeuvre existing
space-based telescopes with instructions from the ground.”
XMM, and Swift images are available from the PPARC web site: www.pparc.ac.uk
or by contacting Gill Ormrod at PPARC press office on 01793 442012. Email: firstname.lastname@example.org
At 3.9 tonnes and 10 metres long, the X-ray Multi-Mirror [XMM]-Newton is the biggest and most sensitive X-ray telescope ever to be placed in to orbit. It is able to study extremely faint X-ray sources from stars and galaxies in the most distant parts of the Universe.
the European Photon Imaging Camera
This instrument, built by an international team of European scientists led by Dr Martin Turner of the University of Leicester uses silicon Charge Coupled Devices to provide simultaneous X-ray images and spectra so that the chemical composition of distant X-ray sources can be studied.
Every day, somewhere in the Universe, there is a gamma ray burst; they are the most powerful and violent phenomena in the Universe. Gamma ray bursts last only a minute or so. But in that
intense burst of gamma rays is followed by an X-ray glow that lasts a few days;
it is this X-ray afterglow that was observed by XMM-Newton about 11 hours after
the gamma ray burst.
ray bursts were discovered in 1967 by the US Military VELA satellites where they
mimicked the signatures of terrestrial nuclear tests. Several thousand have been
detected since, although it was only five years ago that they were proven to
come from distant galaxies.
A supernova is the explosion produced when a massive star ends its life; one occurs in our own Galaxy approximately every hundred years. Seen from the Earth, it would be initially visible in daylight and would be the brightest star in the sky for about six months. Supernovae in distant galaxies appear much fainter, but briefly outshine the host galaxy itself. The chemical elements that make up the Earth, and ultimately ourselves, were formed in supernovae.
of Leicester, Department of Physics & Astronomy
Dr James Reeves, Tel: 0116 2523510, Email: email@example.com
Dr Julian Osborne, Tel: 0116 2523598, Email: firstname.lastname@example.org
Dr Paul O'Brien, Tel: 0116 2525203, Email: email@example.com
Space Science Laboratory, University College London:
Professor Keith Mason, Email: firstname.lastname@example.org (Not available on April 3rd)
XMM-Newton Project Scientist, ESTEC, Noordwijk, Netherlands
Dr Fred Jansen Tel: 0031 71 5654426, Email: email@example.com
J N Reeves, D Watson, J P Osborne, K A Pounds, P T O'Brien, A D T Short, M J L Turner,
M G Watson, K O Mason, M Ehle & N Schartel
Particle Physics and Astronomy Research Council (PPARC) is the UK's strategic
science investment agency. It funds research, education and public understanding
in four areas of science - particle physics, astronomy, cosmology and space
is government funded and provides research grants and studentships to scientists
in British universities, gives researchers access to world-class facilities and
funds the UK membership of international bodies such as the European Laboratory
for Particle Physics (CERN), and the European Space Agency. It also contributes
money for the UK telescopes overseas on La Palma, Hawaii, Australia and in
Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh
and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at
Jodrell Bank observatory.
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