Most people think of black holes as giant vacuum cleaners sucking in everything that gets too close. But the supermassive black holes at the centers of galaxies are more like cosmic engines, converting energy from infalling matter into intense radiation that can outshine the combined light from all surrounding stars. If the black hole is spinning, it can generate strong jets that blast across thousands of light-years and shape entire galaxies. These black hole engines are thought to be powered by magnetic fields. For the first time, astronomers have detected magnetic fields just outside the event horizon of the black hole at the center of our Milky Way galaxy.

A research team including Kazunori Akiyama (postdoctoral fellow at the Japan Society for the Promotion of Science, staying at MIT’s Haystack Observatory) and Mareki Honma (professor at National Astronomical Observatory of Japan) used the Event Horizon Telescope (EHT) – a global network of radio telescopes that link together to function as one giant telescope the size of Earth. The team measured how the radio wave at a wavelength of 1.3 mm is linearly polarized and found that magnetic fields in some regions near the black hole are disorderly, with jumbled loops and whorls resembling intertwined spaghetti. In contrast, other regions showed a much more organized pattern, possibly in the region where jets would be generated. They also found that the magnetic fields fluctuated on short time scales of only 15 minutes or so.

The research result was published as M. D. Johnson et al., “Resolved magnetic-field structure and variability near the event horizon of Sagittarius A*” published in Science on December 4, 2015.

Link

• Event Horizon Telescope Reveals Magnetic Fields at Milky Way’s Central Black Hole (Center for Astrophysics, Harvard-Smithsonian)