BOSTON, For the first time, astronomers have observed magnetic fields just outside a black hole’s event horizon. The fields were located near the super massive black hole at the center of the Milky Way galaxy, Sgr A* or Sagittarius A-star.
Researchers shared their observations in the latest issue of the journal Science.
“Understanding these magnetic fields is critical. Nobody has been able to resolve magnetic fields near the event horizon until now,” lead study author Michael Johnson, a scientist at the Harvard-Smithsonian Center for Astrophysics, said in a press release.
The event horizon is the edge of the area of space-time in which gravitational pull of a black hole can be seen to affect matter and energy.
“These magnetic fields have been predicted to exist, but no one has seen them before. Our data puts decades of theoretical work on solid observational ground,” explained principal investigator Shep Doeleman, also a CfA researcher and assistant director of MIT’s Haystack Observatory.
Though Sgr A* is 4 million times the mass of the sun, its event horizon stretches just 8 million miles across. At 25,000 light-years away, it’s very hard to zoom in on with even the most powerful telescopes. But because the gravity of supermassive black holes’ warp the light as matter and energy is sucked to its center, the event horizon appears magnified.
The magnetic fields were seen using the Event Horizon Telescope, which isn’t a single telescope but a system of radio telescopes working in coordination around the world. Scientists used the network to study the polarized light surrounding Sagittarius A-star.
Polarized light is emitted by electrons spinning around the lines of the black hole’s magnetic fields, thus revealing the fields themselves.
The field lines surrounding the event horizon were varied. In some regions they appeared disorganized and tangled, featuring intertwined loops. In other regions they were more patterned. Researchers believe such regions might be the birthplace of the jets shot out by the black hole’s accretion disk.
“Once again, the galactic center is proving to be a more dynamic place than we might have guessed,” says Johnson. “Those magnetic fields are dancing all over the place.”
By Brooks Hays