While many galaxies have a highly active central black hole, our galactic one is relatively quiet. A new study says the magnetic field might be the reason.
When a supermassive black hole is active, it means it is consuming a lot of material from its galaxy. And when black holes eat, they emit vast amounts of powerful, high-energy radiation into space.
However, the supermassive black hole at the center of our Milky Way, Sagittarius A*, appears to be relatively quiet.
According to NASA, the “relative quiet” could be explained by invisible forces in the heart of the Milky Way.
These invisible forces are powerful magnetic fields, which influence the movement of particles through the galaxy.
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New observations from NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, are helping scientists understand the differences between active and quiet black holes.
Scientists cannot directly image magnetic fields. So, they used SOFIA’s newest instrument, the High-resolution Airborne Wideband Camera-Plus, HAWC+, to make these measurements.
The HAWC+ instrument observes polarised infrared light in deep space, emitted by stellar grains of dust.
These grains align themselves perpendicularly with the magnetic fields, giving astronomers a chance to map their shape and strength.
Joan Schmelz of NASA’s Ames Research Center said: “This is one of the first instances where we can really see how magnetic fields and interstellar matter interact with each other. HAWC+ is a game-changer.”
For the first time ever, SOFIA’s HAWC+ instrument has charted the magnetic fields surrounding the black hole.
NASA said in a statement: “The gravity of the black hole dominates the dynamics of the center of the Milky Way, but the role of the magnetic field has been a mystery.
“The new observations with HAWC+ reveal that the magnetic field is strong enough to constrain the turbulent motions of gas.
“If the magnetic field channels the gas so it flows into the black hole itself, the black hole is active, because it is eating a lot of gas.
“However, if the magnetic field channels the gas so it flows into an orbit around the black hole, then the black hole is quiet because it’s not ingesting any gas that would otherwise eventually form new stars.”
Darren Dowell, a scientist at NASA’s Jet Propulsion Laboratory, suggests the magnetic fields form a spiral shape. That pushes gas into an orbit around the black hole.
This could explain why the black hole does not suck in the gas and is relatively quiet.