Astronomy, new clues to the history of the Milky Way discovered

Discover new clues about the history of the Milky Way, our galaxy, and other galaxies. Thanks to the observations of NASA’s Fermi space telescope, and to an analysis technique that combines signals too weak to be detected individually, an international team of researchers has identified, for the first time, the emissions of gamma rays in some nearby galaxies. to ours produced by the so-called Ufo-Ultra Fast Outflows or ultra-fast ejections. UFOs are real winds of gas and particles emitted at very high speeds by supermassive black holes found in the central regions of galaxies. Scientists believe UFOs play a decisive role in regulating the growth of the black hole itself and its host galaxy. “These new investigations will also allow us to better understand the history of our Milky Way” underline Infn, Inaf and Asi in announcing the discovery. The study was carried out thanks to the data collected by the Lat-Large Area Telescope, an instrument on board Fermi designed and built with a decisive contribution from Italy, thanks to the Italian Space Agency, the National Institute of Nuclear Physics and the National Institute of Astrophysics. The results of this survey, led by Chris Karwin, of the Department of Physics and Astronomy of Clemson University in the United States and which was also attended by Italian researchers, including some from INAF, INFN and ASI, were published today in an article in The Astrophysical Journal. “While these winds are difficult to detect, they are thought to play a significant role in how a massive black hole and the host galaxy itself interact and grow,” said Stefano Marchesi, an INAF researcher in Bologna involved in the study. “Our observations of the gamma rays associated with these ejections show how supermassive black holes can transfer a large amount of energy to their host galaxy. UFOs – explains Marchesi – behave like a piston and accelerate charged particles very efficiently. , known as cosmic rays, up to almost the speed of light. ” “In particular, when compared with the energy transferred to gamma rays from a supernova explosion in the Milky Way – argues Elisabetta Cavazzuti, head of the Fermi program for the Italian Space Agency – this study shows how the winds of active galactic nuclei, if adequately sustained for a few million years, they can supply energy to a large fraction of cosmic rays inside the galaxy, providing an extra piece to the study of these particles “. Each galaxy has a supermassive black hole at its center. Some are quiescent, others, called active galactic nuclei, are active, which means they attract and “swallow” the surrounding matter through a process called accretion. Ufo-Ultra Fast Outflows or ultra-fast ejections are one of the products of the activity of black holes and in their propagation motion through the host galaxies they gradually inhibit the formation of new stars. “Since gamma rays are produced by cosmic rays accelerated in the shock wave generated by the expanding wind – explains Sara Cutini, Infn researcher of the Perugia Section – Fermi’s observations indicate that the UFOs present in our galaxy accelerate charged particles up to to the very high energies of the Peta-electronvolt, to which the spectral transition due to cosmic ray sources located outside our galaxy was traditionally located. “The results of the newly published study will also provide invaluable help to scientists studying the history of our galaxy, the Milky Way and Sagittarius A *, the black hole located in its central regions, which has a mass estimated to be four million times that of the Sun. Researchers recall that above and below the Milky Way’s disk is extend the Fermi bubbles, huge spheroidal structures of hot gas that originate in the galactic center. They are so called because they were discovered in 2010 thanks to the observations made by the Fermi satellite. “Sagittarius A * is not active today, but it probably was in the recent past, perhaps even a few hundred years ago,” Karwin comments. “Our model – he adds – supports the hypothesis that these Fermi bubbles may be remnants of a past UFO-like activity produced by the supermassive black hole at the center of our galaxy”.