Astronomers have detected the magnetic field of a galaxy so distant that its light has taken more than 11 billion years to reach us—that is, we see it as it was when the universe was only 2.5 billion years old.
“Many people may not be aware that our entire galaxy and other galaxies are traversed by magnetic fields, spanning tens of thousands of light years,” said James Geach, professor of astrophysics at the University of Hertfordshire, UK, and author head of the study published today in Nature. However, it is still unclear how early in the life of the universe and how quickly magnetic fields form in galaxies, as astronomers have so far only mapped those in galaxies near us. Now, using the ALMA radio telescope, Geach and his team have discovered a fully formed magnetic field in a distant galaxy, similar in structure to what is observed in nearby galaxies. The field is about 1,000 times weaker than Earth’s magnetic field, but extends more than 16,000 light years.
“This discovery gives us new clues about how magnetic fields form on a galactic scale,” Geach explained. Observing a fully developed one at this early stage in the history of the cosmos indicates that magnetic fields spanning entire galaxies can form rapidly while young galaxies continue to grow.
The team believes that intense star formation in the early universe could have played a role in accelerating the development of magnetic fields, which, in turn, would have influenced how later generations of stars formed. The discovery To make this detection, the team looked for light emitted by dust grains in a distant galaxy, called 9io9. Galaxies are full of dust grains and when a magnetic field is present, the grains tend to align and the light they emit becomes polarized. This means that light waves oscillate along a preferred direction rather than randomly. When ALMA detected and mapped a polarized signal coming from 9io9, the presence of a magnetic field in a very distant galaxy was confirmed for the first time.
«No other telescope could have achieved this. The hope is that with this and future observations of distant magnetic fields, the mystery of how these fundamental galactic features form will begin to be revealed,” Geach concluded.