Cherenkov lightning bolt

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Cherenkov lightning bolts are particle showers triggered by cosmic rays with a duration of only about a billionth of a second. They cannot be seen with the eye.

In the earth's atmosphere, hundreds of high-energy secondary particles are triggered by individual, extremely high-energy gamma radiation quanta from galaxies and supernova remnants at a height of around ten kilometers . Like the gamma quanta themselves, these, in turn, are initially not directly visible, but rather generate a shower of further secondary particles of high energy during the braking process, which cause light flashes directed in the upper atmosphere. The investigation of these luminous phenomena plays an important role in gamma astronomy . The Cherenkov radiation is difficult to observe, although the triggering gamma quanta have enormous energies of a few teraelectron volts (trillion times more than quanta of visible light). They can only be observed from space or with Cherenkov telescopes from the surface of the earth; the photons hitting the ground are in the blue range, which is why the phenomena are sometimes referred to as blue flashes . This observation is interesting for astrophysicists because the origin of such high-energy gamma quanta has not yet been clarified.

The research began in 1989 at the Whipple-Cherenkov telescope , a metal mirror about 10 meters with which an extragalactic gamma source could be observed for the first time from Earth . Another dozen objects were discovered using second-generation instruments, including the HEGRA telescopes on the Canary Island of La Palma . The first large Cherenkov telescope, the High Energy Stereoscopic System (HESS), went into operation in Namibia in 2002 and registers the blue lightning with an arrangement of four large mirrors. The project is supervised by 70 scientists from Europe and Africa . The Max Planck Institute for Nuclear Physics and four other institutes from Germany are involved.

literature

  • Werner Hofmann (Max Planck Institute for Nuclear Physics): Blue flashes from space . In: University of Heidelberg (Ed.): Ruperto Carola . No. 1 , 2003 ( full text , uni-heidelberg.de).

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