Smithsonian Story

A “monster” in the Milky Way Galaxy

March 27, 2024
Marilyn Scallan
lines mark the orientation of polarization, which is related to the magnetic field around the shadow of the black hole

A polarized view of the Milky Way black hole, Sagittarius A*. The lines mark the orientation of polarization, which is related to the magnetic field around the shadow of the black hole. Credit: EHT Collaboration

The Event Horizon Telescope (EHT) collaboration, which includes scientists from the Center for Astrophysics | Harvard & Smithsonian (CfA), has captured a new view of the supermassive black hole at the center of the Milky Way Galaxy. This is the first time astronomers have been able to measure polarization, a signature of magnetic fields, this close to the edge of Sagittarius A* (pronounced "Sagittarius A star").

Scientists unveiled the first image of Sagittarius A* in 2022. Seen in polarized light, this new view of the monster black hole, Sagittarius A*, has revealed a magnetic field structure strikingly similar to that of the black hole at the center of the M87* galaxy, suggesting that strong magnetic fields may be common to all black holes.

supermassive black hole at the center of the Milky Way Galaxy Sagittarius A* is seen in polarized light
The supermassive black hole at the center of the Milky Way Galaxy, Sagittarius A*, is seen in polarized light, the visible lines indicating the orientation of polarization, which is related to the magnetic field around the shadow of the black hole. At center, the polarized emission from the center of the Milky Way, as captured by SOFIA. At back right, the Planck Collaboration mapped polarized emission from dust across the Milky Way. 
Credit: S. Issaoun, EHT Collaboration

“What we're seeing now is that there are strong, twisted, and organized magnetic fields near the black hole at the center of the Milky Way Galaxy,” said Sara Issaoun, CfA NASA Hubble Fellowship Program Einstein Fellow, Smithsonian Astrophysical Observatory astrophysicist, and co-lead of the project. “Along with Sagittarius A* having a strikingly similar polarization structure to that seen in the much larger and more powerful M87* black hole, we’ve learned that strong and ordered magnetic fields are critical to how black holes interact with the gas and matter around them.”

image showing similar black holes
Seen here in polarized light, this side-by-side image of the supermassive black holes M87* and Sagittarius A* indicates to scientists that these titans have similar magnetic field structures. This is significant because it suggests that the physical processes that govern how a black hole feeds and launches a jet may be universal features of supermassive black holes. Credit: EHT Collaboration

This research is a microcosm of the work Smithsonian does in collaboration with different entities across the nation and around the world. The nature of black holes is only a sample of the mysteries of the cosmos waiting to be unraveled.