there ‘cosmic monster“Above our heads, a billion light-years away from us, swallowing massive amounts of matter that partly vomit towards the Earth. And the Blazar Bla Lacertae who, with his Gap
black It is so massive in the center of a huge galaxy, that it actually “swallows a huge amount of matter, which is partially ejected at speeds close to the speed of light in the form of two jets, one of which is pointing almost towards us.” National Institute of Astrophysics (National Institute of Astrophysics)incompatible). Studying this cosmic monster, Il full-earth telescope plazaar (Webt) – a collaboration of astronomers from all over the world in which researchers and researchers from the National Institute of Astrophysics are actively involved – has thus discovered that the radiation of its jets directed towards the Earth exhibits strong periodic fluctuations in brightness, increasing and decreasing within a few hours.
According to the team, “This completely special behavior is due to the fact that the plane is not perfectly straight, but rather a net formed due to the instability created in the plane at a distance of about 16 light-years from Black hole which deviates rhythmically from the strong radiative flux towards us and thus results in the fluctuation of the detected brightness. The work, published in Nature and led by Svetlana Gorstad of Boston University, was attended by researchers from Italian universities and amateur astronomers with some non-professional observers in our country. It was discovered in 1929 in the constellation Lizard (in Latin Lacerta) and initially classified as a variable star, Bla Lac It is the “ancestor” of the class Agn (active galactic nuclei) with similar characteristics: Bl Lacertae organisms.
A blazar is the nucleus of a particular active galaxy (Agn) fed by a substance located in A Black hole The supermassive is located in the center of the galaxy. Scientists show that about 10% of Agn has a pair of jets that are projected into interstellar space at a speed close to the speed of light. INAF adds, “We are talking about an explosion when one of the jets heads almost directly toward Earth, which makes it appear brighter due to the effect of relativistic focus. The jets produce radiation ranging from radio waves to the visible, even X and gamma rays, the intensity of which varies rapidly over time.” “These differences are usually random, with no recognizable pattern,” the researchers add.
The Webt project, started 25 years ago and coordinated by Claudia Maria Raitieri and Massimo Villata of the National Institute of Astrophysics (Inaf), aims to observe the diversity of visible light, but also in radio and near-infrared bands, in blazars observed in gamma rays by satellites. Agile for the Italian Space Agency and Fermi of NASA. “Our observations led to the detection of contrast cycles in visible brightness, in gamma rays, and in the degree of polarization of the BL Lacertae blazar (BL Lac) on a time scale of about 13 hours. Emissions of different wavelengths were recorded in the second half of 2020,” he says. Claudia Raitry of INAF in Turin. BL Lac is powered by a black hole about 170 million times the mass of the Sun and located about a billion light-years from Earth. The cycles of brightness changes are called “quasi-periodic oscillations,” or Qpo. Qpo is often observed in other systems consisting of pairs of black holes with masses between 10 and 50 times the mass of the Sun that emits X-rays.
In the case of the BL Lacertae brightness observations, the team suggested that “a wrinkle forms in the flux that envelops the magnetic field of the same plane, causing the brightness to fluctuate. In addition, another property of the observed brightness is radiation, i.e. its polarization changes with a direction over time similar to that of brightness”. “Polarized light comes from the jet and the polarization can only change if the magnetic field changes its composition in the region that produces the light. The magnetic field in the plane must be twisted to cause the oscillations. The BL Lac observations also show the strength of the relationship between visible light and variations in gamma rays without any delay , which places the origin of the gamma rays in the region where visible light changes”, according to the INAF report.
“If an aircraft’s magnetic field has a helical structure, the jet and the field can become unstable and twist, resulting in puckering. As the particles in the flux flow through the flexure, the amount of radiation emitted increases and decreases rhythmically, resulting in a Qpo.” “However, to further improve the fit between the observations and theory, the researchers inserted the contribution associated with perturbation processes into the code describing the dynamic behavior of the BL Lac jet, and obtained excellent results also in reproducing the detected polarization direction,” adds INAF.
In support of this scenario, images of the jet’s radiation in high-frequency radio waves, obtained by the team with data from the Very Long Baseline Array (Vlba), highlight a new bright spot that has been shifted with respect to the axis of the jet, with a polarization direction favorable to bend formation. in the same plane.
“The goal of Webt is to identify the physical mechanisms that cause variability in plasmids by organizing intense multi-frequency monitoring campaigns and analyzing and interpreting relevant data. The results obtained in Blac were possible thanks to the exceptional temporal continuity of observations that Webt can obtain, due to the cooperation of dozens of astronomers and amateur astronomers observing at different longitudes and thus giving themselves the change in the task of observing within 24 hours of the Earth’s rotation,” Massimo Villata of INAF in Turin and President of Webt since 2000.
(by Andrea Aquino)
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