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Past 70 years astronomers discovered strange objects that are among the most luminous of the universe. Are the so-called objects quasi-stellar or quasars, a few sources of almost the size of stars but emitting as much energy as entire galaxies. With the time it was discovered that quasars are active nuclei, that is to say, supermassive black holes at the centers of galaxies, which are characterized by gobbling stars and gas and emitting huge amounts of radiation. So much so that quasars are authentic brilliant lights visible in the distant universe, and therefore, primitive.
For decades, the knowledge about quasars has been much progress especially thanks to the astronomy of X-rays, radio waves, or gamma rays, allowing to know more about the evolution of the universe in which we live. But just this week, a study published in “Nature” has discovered something amazing in relationship with the quasars. After analyzing the gamma-rays from Centaurus A, the quasar and the radio galaxy nearest to it, the scientists have shown that these quasars are authentic particle accelerators that can reach several thousands of light years long.
composite Image of Centaurus A, with the jets and gamma radiation emitted – ESO/WFI (Optical); MPIfR/ESO/APEX/A. Weiss et al. (Submillimetre); NASA/CXC/CfA/R. Kraft et al. (X-ray), H. E. S. S. collaboration (Gamma)
The scientists thought that the gamma rays emitted by quasars, is generated in the vicinity of the supermassive black holes at the centers of galaxies. The idea is that the processes of accretion, by which the holes gobble up matter accelerated at relativistic speeds, they generate this energetic form of radiation in their vicinity. This would explain why the intensity of this radiation is captured from the Earth can change in a matter of minutes, which fits in with your origin is in a font rather small.
gamma Rays from outside the galaxy
To test this, a team of more than 200 scientists visited the observatory of gamma rays most accurate on the planet: the HESS (High Energy Stereoscopic System”), an observatory located in the Highlands of the Khomas, Namibia. It is a set of five telescopes, with the appearance of satellite dishes covered in mirrors, specialized in capturing the Cherenkov radiation. This allows you to detect the cascade of reactions that produce gamma rays when colliding with the upper parts of the atmosphere of the Land, giving important information on the nature and position of the source, even far beyond the Milky Way.
Observatory, HESS, in Namibia – Wikipedia
to try To decrypt how is the origin of the gamma rays in these quasars, the researchers zeroed in on one of the most close as possible. is why observed Centaurus A, one of the radio galaxies more nearby to the Earth (a radio galaxy is that very light at the wavelength of the radio waves), located 14 million light years (in comparison the Milky Way measures about 200,000 light years long).
Thanks to HESS, and the work of processing and analysis a team of over 200 researchers, they were able to observe this radio galaxy with a resolution not achieved until now, for a total of 200 hours. Thanks to this, she was able to identify the area station of the gamma ray and the trajectory of the two jets of plasma that are born of the quasars, and they are genuine “greatest hits” of matter and radiation expelled from the vicinity of supermassive black holes.
In this way, the observations have shown that the emission of these rays does not occur in the core of quasars, but that occurs around these jets: in fact, this implies that the jets reaceleran particles propelled by black holes and that, therefore, they are authentic particle accelerators that can measure several thousand light years long.
how important is this? Implies that the jets could be the source of the background gamma rays that is observed beyond the Milky Way, and leads to rethink the role of radio galaxies in the distribution of energy in the intergalactic medium.
The next generation of telescopes Cherenkov, headed by the network CTA (“Cherenkov Telescope Array”), will be able to observe these phenomena in greater detail.
