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Galaxies’ spiral arms are formed in sync with their magnetic fields

Magnetic fields in NGC 1086, or M77, are shown as streamlines over a visible light and X-ray composite image of the galaxy from the Hubble Space Telescope, The Nuclear Spectroscopic Array, and the Sloan Digital Sky Survey. NASA/SOFIA; NASA/JPL-Caltech/Roma Tre Univ

If you’ve looked at pictures of the Milky Way, you might have wondered how our galaxy formed its long, spiral arms that reach out from its center. Now, astronomers have gained a clue to this development by looking at another galaxy with spiral arms, NGC 1086, which is located 47 million light-years away in the constellation of Cetus.

The new research from the Stratospheric Observatory for Infrared Astronomy (SOFIA), NASA’s flying observatory, suggests that galaxies’ magnetic fields play a role in the development of spiral arms. As you can see from the image above, the magnetic fields align with the galaxy’s spiral arms, being 24,000 light-years across. Astronomers believe this indicates that the gravitational forces which create the distinctive spiral arms also affect the galaxy’s magnetic field.

“Magnetic fields are invisible, but they may influence the evolution of a galaxy,” Dr. Enrique Lopez-Rodriguez, a Universities Space Research Association scientist at the SOFIA Science Center at NASA’s Ames Research Center, said in a statement. “We have a pretty good understanding of how gravity affects galactic structures, but we’re just starting to learn the role magnetic fields play.”

The arms of the NGC 1086 galaxy are full of dust and gas, which encourages the formation of stars. The areas of intense star formation are known as starbursts. Although the galaxy is similar to our Milky Way in some regards, it also has differences such as a supermassive black hole at its center which is twice as massive as the black hole at the heart of our galaxy.

To gather the data on the magnetic field of this distant galaxy, the astronomers used SOFIA to detect far-infrared light which shows the magnetic field in ways that visible-light telescopes or radio telescopes cannot. This was possible thanks to SOFIA’s most recent addition, an instrument called the High-resolution Airborne Wideband Camera-Plus, or HAWC+.

“This is the first time we’ve seen magnetic fields aligned at such large scales with current star birth in the spiral arms,” Lopez-Rodriquez said. The research is important for supporting one theory of the formation of galactic arms, called the density wave theory: “It’s always exciting to have observational evidence like this from SOFIA that supports theories.”

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