At the heart of the Milky Way galaxy lies Sagittarius A-star (Sgr A*), a supermassive black hole about 25,000 light-years from Earth. It was recently discovered that this colossal celestial object possesses a magnetic field. But while Earth has a magnetic force field to shield against cosmic debris and radiation, Sgr A*’s magnetic field acts more like an engine capable of sending jets of intense radiation across the galaxy.
How Do Magnetic Engines Work?
The black hole, or cosmic engine at the center of the Milky Way, takes energy from infalling matter and converts it to intense radiation. If the black hole spins, then it can send jets of radiation across thousands of light-years. This process was believed to be powered by magnetism and for the first time ever scientists detected a magnetic field just outside the event horizon of Sgr A* using the Event Horizon Telescope (EHT). Despite the unfathomable distance, the EHT allows us to see what’s going on all the way over at the center of the galaxy. The EHT is an Earth-sized, virtual telescope representing the collaboration of a global network of radio telescopes. Because black holes are compact celestial objects, this massive telescope was necessary for seeing the Sgr A* in detail. The Sgr A* weighs about 4 million times as much as the Sun but has an event horizon spanning 8 million miles, which is smaller than Mercury’s orbit. It would be near invisible at this distance if not for its intense gravitational pull, which distorts light and magnifies the event horizon. Using the immense telescope, scientists were able to trace the magnetic field of Sgr A* by measuring the polarization of the light from the black hole as it spirals around magnetic field lines. The light traces the magnetic field because it’s emitted by electrons. By tracing the light, scientists discovered that the magnetic fields in some areas of the accretion disk orbiting Sgr A* are disorderly and jumbled. Other areas, however, follow a more organized pattern and are likely the regions where jets can be generated. As more and more radio dishes are added around the world for the EHT, we can better interpret the dancing of the magnetic fields of Sgr A*.
