The gigantic black hole at the heart of our Milky Way galaxy is coming into sharper focus.
For the first time ever, astronomers have detected magnetic fields just outside the event horizon — the “point of no return” beyond which nothing, not even light, can escape — of the Milky Way’s central supermassive black hole, which is known as Sagittarius A*.
“These magnetic fields have been predicted to exist, but no one has seen them before,” study co-author Shep Doeleman, assistant director of the Massachusetts Institute of Technology’s Haystack Observatory, said in a statement.
“Our data puts decades of theoretical work on solid observational ground.”
This Chandra image shows our Galaxy’s center. The location of the black hole, known as Sagittarius A*, or Sgr A* for short, is arrowed. Credit: NASA/CXC/MIT/Frederick K. Baganoff et al.
Supermassive black holes lurk at the core of most, if not all, galaxies. Sagittarius A*, which lies about 25,000 light-years from Earth, is about 4 million times more massive than the sun, but its event horizon is just 8 million miles (12.9 million kilometers) wide — less than the average distance from Mercury to the sun.
The scientists studied Sagittarius A* using the Event Horizon Telescope (EHT), a system of radio dishes around the world that are linked up to form one enormous instrument sensitive enough to resolve features as small as 15 micro-arcseconds — the equivalent of spotting a golf ball on the moon, study team members said.
The EHT detected polarized light emitted by electrons zipping around Sagittarius A*, which allowed the researchers to trace out the structure of the black hole’s magnetic field. The observations show that this magnetic field is chaotic in some regions and much more orderly in others, including the areas where powerful jets are generated, the researchers said.