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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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