Fifty-five million light-years away, the galaxy M87 hosts a massive black hole that is actively eating infalling gas and dust. As this material spirals in, it generates a massive magnetic field, and that magnetic field acts a bit like a rail gun and fires particles out in a 3,300 light-year long jet.

In new images from the Very Large Array, astronomers have examined the structure of that jet and discovered that it has a delicate double helix structure. These findings are published in The Astrophysical Journal Letters with lead author Alice Pasetto. According to co-author Jose Marti: Helical magnetic fields are expected close to the black hole and are thought to play a highly important role in channeling the material into a narrow jet, but we didn’t expect to find such a strong helical field extending so far outward. 

According to an NRAO press release on this study: …scientists suggested that instabilities in the flow of material within the jet could make the magnetic field more ordered at the distances seen in the new VLA images. The instabilities produce regions of higher pressure which also compress the magnetic field lines. 

These instabilities in turn are thought to produce the distant double helix structure.

This research shows again that we think too small. The Universe once again builds things on a grander scale than we expect.

More Information

NRAO press release

“Reading M87’s DNA: A Double Helix Revealing a Large-scale Helical Magnetic Field,” Alice Pasetto et al., 2021 December 7, The Astrophysical Journal Letters