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HESS discovers 3 extremely luminous gamma-ray sources in another galaxy

For the first time, the High Energy Stereoscopic System (HESS) telescopes have discovered three luminous objects in an external galaxy. The discovery is published in Science. The HESS collaboration involves the Leprince-Ringuet laboratory (École Polytechnique/CNRS).

Left: © Collaboration HESS/Skyview/A. Mellinger.
Right: © Collaboration H.E.S.S./Karl D. Gordon/R. Kennicutt, J.E. Gaustad and al./G. Bothun

The discovery was published in Science on January 23, 2015. 

The international team publishing these results includes researchers from the National Center for Scientific Research (CNRS) and the French Alternative Energies and Atomic Energy Commission. Among them, Mathieu Naurois, research Director at CNRS working at the Leprince-Ringuet Laboratory (École Polytechnique/CNRS), is the deputy spokesperson of the HESS collaboration.

The High Energy Stereoscopic System (HESS) telescopes, located in Namibia, discovered for the first time three objects of stellar origin in another galaxy, which are most luminous very high-energy gamma-ray sources. Very high-energy gamma rays are the best tracers of cosmic extreme events such as supernova remnants and pulsar wind nebulae deriving from massive stars. They can be measured on Earth by observing the Cherenkov light emitted from the particle showers produced by incident gamma rays high up in the atmosphere using large telescopes with fast cameras such as the HESS telescopes.

After 210 hours of cumulative observation of the Large Magellanic Cloud, a dwarf satellite galaxy of our Milky Way, located about 170.000 light years away, the five HESS telescopes detected three sources of stellar origin, different in nature, and among the brightest known to date in this area:
> A pulsar wind nebula, which corresponds to the heart of a massive star collapsed after a supernova explosion;
> A supernova remnant, a supernova being a cataclysmic explosion of a massive star, which is accompanied by a brief but intense increase in brightness;
> And a "superbubble", structure formed by the powerful winds of massive stars and supernovae explosions. The latter represents a new type of gamma-emitting sources in this area of very high energy.

HESS scientists were interested in the Large Magellanic Cloud galaxy because it produces massive stars at a high rate.

For the first time, stellar gamma sources were detected in a galaxy other than the Milky Way.

More information:
> Read the press release from Interactions.org