The phenomenon of cosmic rays, discovered by Nobel Prize winner Dr. Victor Hess in 1912, has received extensive studies on its composition, radiative mechanism and propagation effects. However, the problem of origin of these mysterious rays stays unsolved over the past one hundred or so years.
A new research from an international research group supports that old supernova remnants (SNRs) may produce high energy gamma rays by their interaction with giant molecular clouds (GMCs). The research, co-authored by Dr. TIAN Wenwu from the National Astronomical Observatories of CAS and his Canadian and U.S. colleagues, has been reported by the March 1 issue of
Astrophysical Journal Letters.
According to the report, an SNR, dubbed "W41", is estimated at some 12 thousand light years away from the Earth with an age of ~105 years. It is likely to be associated with a previously-detected extended TeV source HESS J1834-087. With the help of high-resolution radio and X-ray observations, these scholars found that high energy hard X-rays and very high energy γ-rays probably originate from the SNR interaction with a GMC at its center. The observations can be "the first evidence that an old SNR encounters a GMC to emit TeV γ-rays in the cloud material".
The observations employed the XMM-Newton X-Ray Satellite of the European Space Agency as well as the Very Large Array of the US National Radio Astronomy Observatory.
Recent years have witnessed the construction of several high energy telescopes targeting at the detection of origin of cosmic rays. For instance, the Namibia-based HESS is a system of Imaging Atmospheric Cherenkov Telescopes for investigating cosmic gamma rays in the 100 GeV energy range. Since its official inauguration on September 28, 2004, HESS has detected 14 new sources of TeV γ-rays, which aroused heated discussions and more research in the field.