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Possible Origin of Cosmic Rays Revealed with Gamma Rays (Forwarded)



 
 
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Old November 5th 04, 06:54 AM
Andrew Yee
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Default Possible Origin of Cosmic Rays Revealed with Gamma Rays (Forwarded)

Particle Physics and Astronomy Research Council
Swindon, U.K.

Contacts:

Dr. Paula Chadwick
Department of Physics
University of Durham
Tel +44 191 334 3560
Mobile +44 781 202 9934

Julia Maddock
PPARC Press Office
Tel +44 1793 442094
Mobile +44 7901 514 975

Durham Press Office Contact
Keith Seacroft
Tel +44 191 334 6077

4 November 2004

Possible Origin of Cosmic Rays Revealed with Gamma Rays

A team of UK astronomers working with international partners has produced the
first ever image of an astronomical object using high energy gamma rays, helping
to solve a 100 year old mystery -- the origin of cosmic rays. Their research,
published in the Journal Nature on November 4th, was carried out using the High
Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia,
South-West Africa.

The astronomers studied the remnant of a supernova that exploded some 1,000
years ago, leaving behind an expanding shell of debris which, seen from the
Earth, is twice the diameter of the Moon. The resulting image helps to solve a
mystery that has been puzzling scientists for almost 100 years -- the origin of
cosmic rays. Cosmic rays are extremely energetic particles that continually
bombard the Earth, thousands of them passing through our bodies every day. The
production of gamma rays in this supernova shock wave tells us that it is acting
like a giant particle accelerator in space, and thus a likely source of the
cosmic rays in our galaxy.

Dr Paula Chadwick of the University of Durham said, "This picture really is a
big step forward for gamma-ray astronomy and the supernova remnant is a
fascinating object. If you had gamma-ray eyes and were in the Southern
Hemisphere, you could see a large, brightly glowing ring in the sky every night."

Professor Ian Halliday, CEO of PPARC which funds UK participation in HESS said,
"These results provide the first unequivocal proof that supernovae are capable
of producing large quantities of galactic cosmic rays -- something we have long
suspected, but never been able to confirm."

Gamma rays are the most penetrating form of radiation we know, around a billion
times more energetic than the X-rays produced by a hospital X-ray machine. This
makes it very difficult to use them to create an image -- they just pass
straight through any surface which we might use to reflect them, for instance.
However, luckily for life on Earth, gamma rays from objects in outer space are
stopped by the atmosphere; when this happens, a faint flash of blue light is
produced, lasting for a few billionths of a second. The astronomers used images
of these flashes of light, called Cherenkov radiation, to make a gamma ray
'image' for the first time.

The 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 science.

PPARC 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.

PPARC's Public Understanding of Science and Technology Awards Scheme funds both
small local projects and national initiatives aimed at improving public
understanding of its areas of science.

Notes for Editors:

The H.E.S.S. collaboration
The High Energy Stereoscopic System (H.E.S.S.) team consists of scientists from
Germany, France, the UK, the Czech Republic, Ireland, Armenia, South Africa and
Namibia.

The H.E.S.S. array
Over the last few years, the H.E.S.S. collaboration have been building a system
of four telescopes in the Khomas Highland region of Namibia, to study
very-high-energy gamma rays from cosmic particle accelerators. The telescopes,
known as Cherenkov telescopes, image the light created when high-energy cosmic
gamma rays are absorbed in the atmosphere, and have opened a new energy domain
for astronomy. The H.E.S.S. telescopes each feature mirrors of area 107 square
metres, and are equipped with highly sensitive and very fast 960-pixel light
detectors in the focal planes. Construction of the telescope system started in
2001; the fourth telescope was commissioned in December 2003. Observations were
being made even while the system was being built, first using a single
telescope, then with two and three telescopes. While only the complete
four-telescope system provides the full performance, the first H.E.S.S.
telescope alone was already superior to any of the instruments operated
previously in the southern hemisphere. Among the first targets to be observed
with a two-telescope instrument was the Galactic Centre.

Project images,
http://www.mpi-hd.mpg.de/hfm/HESS/pu...ull_images.htm

For further information, see the project website,
http://www.mpi-hd.mpg.de/hfm/HESS/

Images

Gamma ray image
[http://www.pparc.ac.uk/Nw/Md/Artcl/g..._supernova.jpg (537KB)]
The first astronomical image in very high energy gamma rays -- supernova remnant
RXJ1713.7-3946. The remnant is about twice the diameter of the moon.
Superimposed for comparison are the contours of the X-ray emission observed with
the ASCA satellite.

Supernova images are available from the Hubble website,

http://hubblesite.org/newscenter/new...tar/supernova/

Diagram of gamma rays in atmosphere,
http://www.pparc.ac.uk/Nw/Md/Artcl/Cherenkov_hres.gif (7KB)

*****

Observatoire de Paris
Paris, France

Contacts:
Catherine Boisson
Observatoire de Paris, LUTH
Tél: 33 1 45 07 74 36
Fax: 33 1 45 07 74 69


Helène Sol
Observatoire de Paris, LUTH
Tél: 33 1 45 07 74 28
Fax: 33 1 45 07 74 69


4 November 2004

First image of TeV-energy gamma-rays of a supernova remnant

The new instrument H.E.S.S. (High Energy Stereoscopic System) composed of 4
Cherenkov 13m-telescopes in Namibia, has just made a map of the very high energy
gamma-rays, of the order of Tera electron-volt (TeV) of the supernova remnant RX
J1713.7-3946. This is the first map in TeV gamma-rays ever done of an
astronomical object. It demonstrates directly that supernova shells are indeed
able to accelerate charged particles up to more than 100 TeV. This first
discovery is reported in a Nature article, co-authored by astronomers of Paris
Observatory.

Reference

Direct evidence for high-energy particle acceleration in the shell of a
supernova remnant
Aharonian et al, Nature, 4 November 2004,
http://www.obspm.fr/actual/nouvelle/nov04/psr.pdf

IMAGE CAPTION:
[http://www.obspm.fr/actual/nouvelle/nov04/snr-f1.jpg (121KB)]
Image in linear color scales of TeV gamma-rays from the supernova remnant RX
J1713.7-3946. The spatial resolution from H.E.S.S. is of 3 arcmin. The
superposed contours, in linear scales, are the X-rays of 1-3 KeV from ASCA, with
a comparable resolution.

 




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