NASA | Ames Research Center | USRA | SOFIA | 2019 Jun 11
SOFIA observations reveal a strong magnetic field with a spiral shape at the center of the Milky Way that could explain why our galaxy’s black hole is “quiet”
Supermassive black holes exist at the center of most galaxies, and our Milky Way is no exception. But many other galaxies have highly active black holes, meaning a lot of material is falling into them, emitting high-energy radiation in this “feeding” process. The Milky Way’s central black hole, on the other hand, is relatively quiet. New observations from NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, are helping scientists understand the differences between active and quiet black holes.Streamlines showing magnetic fields layered over a color image of the dusty ring
around the Milky Way’s massive black hole. The Y-shaped structure is warm
material falling toward the black hole, which is located near where the two arms
of the Y-shape intersect. The streamlines reveal that the magnetic field closely
follows the shape of the dusty structure. Each of the blue arms has its own field
that is totally distinct from the rest of the ring, shown in pink.
Credits: Dust and magnetic fields: NASA/SOFIA; Star field image: NASA/HST
These results give unprecedented information about the strong magnetic field at the center of the Milky Way galaxy. Scientists used SOFIA’s newest instrument, the High-resolution Airborne Wideband Camera-Plus, HAWC+, to make these measurements.
Magnetic fields are invisible forces that influence the paths of charged particles, and have significant effects on the motions and evolution of matter throughout the universe. But magnetic fields cannot be imaged directly, so their role is not well understood. The HAWC+ instrument detects polarized far-infrared light, which is invisible to human eyes, emitted by celestial dust grains. These grains align perpendicular to magnetic fields. From the SOFIA results, astronomers can map the shape and infer the strength of the otherwise invisible magnetic field, helping to visualize this fundamental force of nature. ...
Previous observations from SOFIA show the tilted ring of gas and dust orbiting the Milky Way’s black hole, which is called Sagittarius A* (pronounced “Sagittarius A-star”). But the new HAWC+ data provide a unique view of the magnetic field in this area, which appears to trace the region’s history over the past 100,000 years. ...