Dark particle accelerator in the center of the Milky Way

HESS telescopes discover hitherto unknown sources of high-energy gamma radiation

The Milky Way in different wavelengths © HESS-Collaboration
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Eight new sources of high-energy gamma radiation have been found by a team of international scientists using the HESS telescope system. With the discovery, the number of previously known sources has almost doubled. The surprising research results are published in the new issue of the international journal "Science".

High-energy gamma radiation is a form of electromagnetic radiation from the cosmos - a light invisible to human eyes, with energy thousands of billion times larger than the energy of visible light. The atmosphere of our earth is constantly struck by a stream of high-energy nuclear particles from outer space - the cosmic radiation. Cosmic radiation is generally considered to be the driving force for the evolution of the universe and one of the motors of evolution, as it promotes the development of life on Earth through genetic changes in plants and animals.

The cosmic radiation was discovered in 1912 by Viktor Hess, who received the Nobel Prize for Physics for this discovery in 1936. But the origins of the radiation from space remain hidden so far. Scientists have been searching for sources of cosmic radiation for nearly a hundred years. An indication of possible sources is the detection of high-energy gamma radiation. Wherever it occurs, one also suspects sources of cosmic radiation.

Four eyes in the Milky Way

The High Energy Stereoscopic System (HESS), an ensemble of four telescopes, built specifically for the detection of high-energy gamma radiation, is located in the Khomas Highlands of Namibia. From there, the scientists have an almost ideal view of the central area of ​​the Milky Way. The HESS telescope system, which only went into operation in December 2003, is considerably more sensitive than all previous telescopes of this type and makes it possible for the first time not only to search selectively for sources of high-energy gamma radiation but to look at the entire area of ​​the central Milky Way.

Even the first such observations brought unsuspected successes. So far, about twelve source objects of high energy radiation have been known. The HESS researchers have now succeeded in finding a new population of eight sources of this radiation. "We had hoped to discover new sources with an instrument like HESS. However, that we would immediately have such a success, exceeds our wildest expectations, "said Stefan Funk from the Max Planck Institute for Nuclear Physics in Heidelberg. display

Galactic radiation sources are riddles

The discovery of the international research team is remarkable not only because of the number of new sources. Some of the found objects are of several light years - for comparison, the distance from Earth to our nearest stellar neighbor "Alpha Centauri" is four light-years. Above all, the scientists are surprised that there are no counterparts in other areas of the electromagnetic spectrum for some of the newly discovered sources. Obviously, these sources can only be detected in the range of high-energy gamma radiation, but not in visible light as sources of radio or X-rays.

"Here we are faced with a big riddle: we are dealing with a completely new kind of galactic sources and have no idea how the detected gamma radiation is generated in these objects, " says Stefan Funk. Thus, the HESS project has already achieved the second important discovery in a few months. Already during the start-up phase of the experiment, the international team of scientists was able to produce for the first time a high-resolution image of a gamma radiation source, a supernova remnant. The trade magazine "Nature" reported. The new discoveries are a great success for the still young research in gamma-ray astronomy. They open up a new view of the cosmos and allow deep insights into the origins of cosmic radiation.

(MPG, 29.03.2005 - NPO)