Press release on behalf of PPARC
The center of the galaxy in the X-ray field. Credit: HESS collaboration
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A team of astronomers from the UK, in collaboration with teams around the world, discovered a mysterious object emitting energetic gamma rays at the center of our Milky Way Galaxy. Their research, published on September 22 in the Journal of Astronomy and Astrophysics, was conducted using the SSEH (High Energy Spectroscopic System). It is an array of four telescopes, located in Namibia, South West Africa.
The center of our galaxy contains several possible sources of gamma rays, such as a supermassive black hole, remnants of supernova explosions, and possibly also accumulations of exotic dark matter particles, with each of the possibilities raised emitting gamma radiation in a slightly different way. The origin of the radiation discovered by the HESS team is in the region near the Sagittarius constellation, the region where the black hole at the center of our galaxy resides.
According to most theories of dark matter, the radiation discovered is too energetic to be explained by the ionization of dark matter particles. The radiation spectrum obtained best fits the theories, which hold that the source of the energy is a huge supernova explosion. Such an explosion should produce a steady stream of radiation.
Dr. Paula Chadwick (Chadwick) from Durham University said "We know that a giant supernova exploded in this region 10,000 years ago. Such an explosion may accelerate cosmic gamma radiation to such high energies as we have seen - radiation whose intensity is a billion times greater than the X-ray radiation used in hospitals. However, we will need additional observations to determine the exact source of the radiation."
Professor Ian Halliday, CEO of the Astronomical and Astrophysical Research Council (PPARC), which funds the English involvement in HESS, said: "Science continues to reveal the unexpected as we push to the forefront of knowledge." Holliday added "The center of our galaxy is a mysterious place and home to mysterious phenomena such as black holes and dark matter. Finding the source of the gamma rays will tell us a lot about the processes taking place in the heart of our galaxy."
However, the team's theory is inconsistent with previous results obtained by the Australian-Japanese CANGAROO team and the US Whipple team. Both of these teams had previously discovered energetic gamma rays from the center of the galaxy (in observations conducted in 1995-2002), although their observations did not reach the accuracy reached by HESS, and in addition, these teams were unable to locate the exact location of the gamma rays. The previous results have different characteristics than the HESS observations. It is possible that the gamma ray source at the center of the galaxy changes over a period of one year, making it a variable object, such as the black hole at the center of the galaxy.
The HESS team hopes to unravel the mystery with additional observations of the galactic center over the next year or two. The complete array of the four telescopes will be inaugurated on September 29, 2004.
Translation: Dikla Oren
Abstract of the scientific article
The press release on behalf of PPARC
Knowledge of astrophysics - stars and galaxies
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