The particularity of gamma radiation is not its composition (it is made of photons, like visible light), but the energy it carries. It is of the order of an electronvolt (eV) for visible light. Gamma rays can carry a million million electronvolts, or one teraelectronvolt (TeV). And researchers now have instruments capable of detecting this type of radiation.
Thanks to the Hawc observatory (High-Altitude Water Cherenkov), THE astronomersastronomers have even already observed, in less than 10 years, nearly 100 gamma events which they describe as very high energy. Understand, gamma rays of more than 100 TeV! It must be said that the Hawc is a somewhat special observatory. It is placed on the side of volcanovolcanoin Mexico, at more than 4,000 meters above sea level. It is an observatory made up of hundreds of tanks of water and detectors which capture the traces of charged particles which move very quickly. Like those produced when gamma rays reach us.
A source of very high energy gamma rays at the center of the galaxy
In The Astrophysical Journal Lettersan international team of researchers led by the Los Alamos National Laboratory (United States) today tells how it has not only observed very high energy gamma rays, but also for the first time, traced their origin to the center of the Milky Way. “This work confirms for the first time the presence of a source of very high energy gamma rays at a location in the Milky Way known as the Milky Way ridge. galactic centergalactic centerwhich means that the galactic center is home to some of the processes physiquesphysiques the most extreme of our UniverseUniverse »specifies Pat Harding, physicistphysicistin a press release from Los Alamos National Laboratory.
Physicists call this source the PeVatron. The phenomenon still remains mysterious to astronomers themselves. What they know is that in this region of the Milky Way, we find a supermassive black holesupermassive black holethe famous Sagittarius A*, surrounded byneutron starsneutron stars and of white dwarfswhite dwarfs who tear away mattermatter to neighboring stars. But everything is wrapped in cloudsclouds of gazgaz dense at several million degrees. Enough to make its direct observation impossible. Hence the interest of researchers in the gamma rays coming from the region.
The secrets of PeVatron
Because the PeVatron gets its name from the fact that astronomers suspect the presence of a source that accelerates particles up to a million billionelectron voltselectron voltsone petaelectronvolt (PeV). Enough to make them travel at more than 99% of the speed of light. And produce the famous very high energy gamma rays. In the minds of scientists, to produce such energies requires extremely violent physical processes. A black hole that swallows up another black hole, for example. What puzzles researchers is that they do not expect this type of very rare phenomenon to occur in a galaxygalaxy like our Milky Way. SO…
The Milky Way’s black hole could bombard us with cosmic rays
To learn a little more about the PeVatron, physicists are now waiting with undisguised impatience for the start-up of a new installation for the observation of gamma rays. THE SouthernSouthern Wide-field Gamma-ray Observatory is in the process of constructionconstruction in the Atacama Desert (Chile). It should allow you to open a windowwindow a little wider even than the HAWC at the center of our Milky Way. And, perhaps, finally reveal the mystery of the extreme physical processes at play therent.
