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"The spiral shape of the magnetic field channels the gas into an orbit around the black hole," said Darren Dowell, scientist at NASA's Jet Propulsion Laboratory, principal investigator of the HAWC + instrument and lead author of the 39, study on the central black of Milky Way. hole. "It could explain why our black hole is calm while others are active.
Supermassive black holes exist in the center of most galaxies, and our Milky Way is no exception. But many other galaxies have very active black holes, which means that a lot of materials fall there, emitting high energy radiation in this "feeding" process. In contrast, the central black hole of the Milky Way is relatively calm. SOFIA, NASA's Stratospheric Observatory for Infrared Astronomy, helps scientists understand the differences between active and silent black holes.
A future quasar?
Far in the future, however, through violent events such as the Milky Way's next collision with the Great Magellanic Cloud, "our descendants, if any, will be treated to a treat: a spectacular fire show Cosmic artifacts like the supermassive black hole recently The center of our galaxy, Sagittarius A *, reacts by emitting jets of extremely bright energy radiations, "says Carlos Frenk, director of the Institute of Computational Cosmology's University of Durham.
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"The destruction of the Great Magellanic Cloud, devoured by the Milky Way, will wreak havoc in our galaxy, waking up the black hole that lives in its center and turning our galaxy into an" active galactic core "or" quasar "" citing the galactic. Astrophysicist Marius Cautun and the Institute of Computational Cosmology at Durham University about a new research project foreseeing the collision of our galaxy with the Great Magellanic Cloud in two billion years ago .
Back to the quiet present
These results provide unprecedented information on the strong magnetic field at the center of the Milky Way galaxy. Scientists used SOFIA's newest instrument, the higher resolution broadband airborne camera, HAWC +, to perform these measurements.
The current lines showing the magnetic fields are superimposed on a color image of the dusty circle around the massive black hole above the Milky Way. The Y-shaped structure is a hot material that falls to the black hole, located near the intersection of the two arms of the Y shape. The current lines reveal that the magnetic field closely follows the shape of the structure dusty. Each of the blue arms has its own field totally distinct from the rest of the ring, in pink. Credit: Dust and magnetic fields: NASA / SOFIA; Image of star field: NASA / Hubble Space Telescope
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Magnetic fields are invisible forces that influence the trajectory of charged particles and have important effects on the movements and evolution of matter throughout the universe. But magnetic fields can not be visualized directly, so their role is not well understood. The HAWC + instrument detects the polarized infrared light emitted by celestial dust particles, invisible to the eyes of humans. These grains align perpendicular to the magnetic fields. From the results of SOFIA, astronomers can map the shape and deduce the force of the otherwise invisible magnetic field, helping to visualize this fundamental force of nature.
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"This is one of the first cases where we can really see how magnetic fields and interstellar matter interact," said Joan Schmelz, an astrophysicist at the University Space Research Center at NASA Ames Research Center in Silicon Valley. , in California. an article describing the observations. "HAWC + is a game changer."
Previous observations of SOFIA show the inclined ring of gas and dust in orbit around the black hole of the Milky Way, called Sagittarius A * (pronounced "A star Sagittarius"). But the new HAWC + data provides a unique view of the magnetic field in this area, which seems to trace the history of the region over the last 100,000 years.
The details of these SOFIA magnetic field observations were presented at the June 2019 meeting of the American Astronomical Society and will be submitted to the Astrophysical Journal.
The gravity of the black hole dominates the dynamics of the center of the Milky Way, but the role of the magnetic field remained a mystery. New observations with HAWC + reveal that the magnetic field is strong enough to constrain turbulent gas movements. If the magnetic field channels the gas so that it enters the black hole itself, the black hole is active because it consumes a lot of gas. However, if the magnetic field channels the gas to orbit the black hole, it is silent because it does not absorb any gas that would otherwise form new stars.
Researchers have associated medium and far infrared images from SOFIA cameras with new contoured lines to visualize the direction of the magnetic field. The Y-shaped blue structure (see figure) is a hot material falling towards the black hole near the intersection of the two arms of the y-shape. By superimposing the structure of the magnetic field on the image, it is found that the magnetic field follows the shape of the dusty structure. Each of the blue arms has its own field component, totally different from the rest of the ring, in pink. But there are also places where the field moves away from the main dust structures, such as the upper and lower ends of the ring.
The new SOFIA and HAWC + observations help to determine how the materials in the extreme environment of a supermassive black hole interact with it, notably by answering a long-standing question: Why the Central Black Hole of the Way milk is relatively low while those of other galaxies are also bright.
The Daily Galaxy via Kassandra Bell and Joan Schmelz of NASA
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