VLA Images Reveal The Double Propeller Structure Of The Jet Emitted From The Black Hole Of The M87

Astronomers using the National Science Foundation’s (VLA) Very Large Array Karl G. Jansky have shown that a jet of material propelled from the center of a giant galaxy is channeled by a corkscrew-shaped magnetic field to nearly 3,300 light-years away of the central black hole of the galaxy. This is much further away than this magnetic field has ever been detected in a galactic jet.

“By taking high-quality images with the VLA at several different radio wavelengths of the Messier 87 (M87) galaxy, we were able to reveal the three-dimensional structure of the magnetic field in this jet for the first time,” said Alice Pasetto of the National Autonomous University from Mexico, team leader. “The material of this jet traces a double helix, similar to the structure of DNA,” he added.

M87 is a giant elliptical galaxy that is about 55 million light years from Earth. A supermassive black hole about 6.5 billion times the mass of the Sun lurks at the center of M87. This black hole is famous because it was the first to be photographed – an achievement made with the worldwide Event Horizon Telescope (EHT) collaboration and announced in 2019. Earlier this year, new EHT images traced the magnetic field in the vicinity of the black hole Event horizon.

Pasetto and his colleagues used the VLA to reveal details of the magnetic field by tracing the polarization, or alignment, of the radio waves emitted by it and measuring the field strength in different parts of the jet. His observations, made using the widest VLA setting that provides the highest resolution, produced very detailed images of the galaxy’s jet.

“Helical magnetic fields are expected near the black hole and are expected to play a very important role in channeling the material into a narrow jet, but we didn’t expect to find such a strong helical field extending that far,” said Jose M. Marti of the University of Valence.

The magnetic field is expected to weaken with its distance from the black hole. However, scientists have suggested that instabilities in material flow within the jet could make the magnetic field more orderly at distances seen in the new VLA images. Instabilities produce regions of greater pressure that also compress the magnetic field lines.

Astronomers think that this interaction between the flux instabilities and the magnetic field is what produces the double helix structure shown by the VLA images. If this is happening on the M87 jet, it’s probably also happening on similar jets from galaxies across the Universe, they said.

“The M87 is relatively close to us and its jet is very powerful, which makes it an excellent target for studies. The clues it gives us can help us understand this very important and omnipresent phenomenon in the Universe”, said Jose L. Gomez, from the IAA-CSIC, Granada.

Scientists are reporting their findings on Astrophysical Journal Letters .

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under a cooperative agreement of the Associated Universities, Inc.

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VLA Reveals Double-Helix Structure in Massive Galaxy’s Jet