The Atacama Large Millimeter/submillimeter Array (ALMA) has detected the magnetic field of a distant galaxy whose light traveled more than 11 billion years before reaching us. We see the galaxy as it was when the universe was only 2.5 billion years old. The result gives astronomers key clues about how the magnetic fields of galaxies like our own Milky Way are created.
Many astronomical objects in the universe, whether planets, stars or galaxies, have magnetic fields. “Many people may not realize that our entire galaxy and other galaxies are surrounded by a magnetic field that extends tens of thousands of light-years,” said James Geach, professor of astrophysics at the University of Hertfordshire and lead author of the study published in the journal. Nature magazine.
“We actually know very little about how these fields form, even though they are fundamental to the evolution of galaxies,” added Stanford University researcher Enrique Lopez Rodriguez, who also participated in the study. It is not yet clear how early the universe was and how quickly magnetic fields formed in galaxies, because astronomers have so far only mapped magnetic fields in galaxies near us.
However, using ALMA, Geach and his team detected the magnetic field of a distant galaxy with a structure very similar to that observed in nearby galaxies. This field is about a thousand times weaker than the Earth’s magnetic field, but it extends for more than 16,000 light-years.
“This discovery gives us new clues about the formation of magnetic fields on a galactic scale,” explained Geach. Observations of a fully developed magnetic field early in the history of the universe indicate that galaxy-spanning magnetic fields could evolve very rapidly, even during galaxy growth.
The research group believes that intense star formation in the early universe may have played a role in accelerating the evolution of these fields. Moreover, these fields can influence the formation of subsequent generations of stars. Co-author Rob Ivison, an astronomer at the European Southern Observatory, said the discovery “opens a new window on the inner workings of galaxies, where magnetic fields bind to the material that forms new stars.”
To discover the magnetic field, the research team looked for light emitted by dust particles in the distant galaxy 9io9. Galaxies are filled with dust grains, and in the presence of a magnetic field, the grains tend to line up with each other, so the light they emit becomes polarized. This means that light waves do not oscillate randomly, but rather in a preferred direction. ALMA’s discovery and mapping of the polarized signal from 9io9 confirmed the presence of a magnetic field in a very distant galaxy for the first time.
“No other telescope can achieve this,” Geach said. With these observations and future observations of distant magnetic fields, the mystery of how these fundamental galactic features are formed will begin to unravel.
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