Extensive analysis has conclusively linked galaxies harboring bright, energetic nuclei known as blazars to the source of high-energy neutrinos, enigmatic extragalactic “ghost” particles that accelerate cosmic rays and generate strange phenomena: although hardly they have mass, they are one of the most abundant particles in the Universe.
An international team of researchers has revealed for the first time the origin of the high energy neutrinos, elementary particles that reach our planet from the depths of the Universe. Scientists believe that neutrinos are born in blazars, galactic nuclei fueled by supermassive black holes. The results have recently been published in the Astrophysical Journal Letters.
solving the mystery
Most of the “normal” neutrinos that can be detected on Earth are byproducts of solar nuclear reactions, although they can also be produced by supernovae, artificial nuclear reactions, or interactions between cosmic rays and atoms. However, in 2012 the IceCube Neutrino Observatory located in Antarctica detected two neutrinos that were unlike anything previously observed, given their behavior and high energy. These high energy neutrinos they came from intergalactic space, but with unknown origin.
Extremely energetic and difficult to detect, high-energy neutrinos travel billions of light years before reaching our planet. Although it is known that you are elementary particles come from the depths of the Universe, its precise origin is still unknown. They have practically no mass and barely interact with matter: they can travel through galaxies, planets and the human body with almost no trace.
According to a press release from the University of Geneva (UNIGE), in Switzerland, one of the academic centers that led the research, the results of the new study allow us to conclude that high-energy neutrinos are born in blazars, a compact and intensely variable source of energy, associated with supermassive black holes located in the center of galaxies. Blazars are among the most violent and extreme phenomena in the Universe.
Neutrinos and cosmic rays
At the same time, as neutrinos are produced exclusively in processes that involve the acceleration of cosmic rays, they become “messengers” capable of paving the way to identify cosmic ray sources, another of the great astrophysical mysteries. The new research could thus begin to solve two great enigmas at the same time: the origin of neutrinos, considered the most elusive particles in the Universe, and the source from which cosmic rays come.
Earth’s atmosphere is constantly bombarded by cosmics rays, electrically charged particles with energy flows up to a million times higher than the energy reached in the most powerful particle accelerator in the world, the Large Hadron Collider (LHC). For more than a century, scientists have wondered what shoots cosmic rays through the Universe with such a powerful force.
Because cosmic rays carry an electrical charge, the galaxy’s magnetic fields can deflect them as they travel through space, making it almost impossible for specialists to trace where they originated. However, by identifying the source from which the neutrinos are born, the origin of cosmic rays could be discovered at the same time, since it has been proven that these are accelerated by neutrinos.
The team of scientists in charge of the new study, led by astrophysicist Sara Buson, maintains that the accretion process and the rotation of the supermassive black holes they lead to the formation of relativistic jets, in which particles accelerate and emit radiation up to extremely high energies. These powerful jets or blazars and their connection with neutrinos and cosmic rays could become the Holy Grail of contemporary astrophysics, generating an unprecedented revolution in this field of scientific knowledge.
Beginning a Journey Across the Universe: The Discovery of Extragalactic Neutrino Factories. Sarah Buson et al. The Astrophysical Journal Letters (2022). DOI:https://doi.org/10.3847/2041-8213/ac7d5b