Furthest ever detection of a galaxy’s magnetic field – study

Astronomers have detected the magnetic field of a galaxy so far away that its light has taken more than 11 billion years to reach Earth.

It is seen as when the universe was just 2.5 billion years old.

Researchers say the result provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way came to be.

James Geach, a professor of astrophysics at the University of Hertfordshire, said: “Many people might not be aware that our entire galaxy and other galaxies are laced with magnetic fields, spanning tens of thousands of light years.”

Enrique Lopez Rodriguez, a researcher at Stanford University, USA – who also participated in the study, added: “We actually know very little about how these fields form, despite their being quite fundamental to how galaxies evolve.”

Because astronomers have only mapped magnetic fields in galaxies close to us, it is not clear how early in the lifetime of the universe, and how quickly, magnetic fields in galaxies form.

Using the Atacama Large Millimetre/submillimetre Array (Alma) which the European Southern Observatory (ESO) is a partner, the researchers have discovered a fully formed magnetic field in a distant galaxy, similar in structure to what is observed in nearby galaxies.

According to the experts, the field is about 1000 times weaker than the Earth’s magnetic field, but extends over more than 16 000 light years.

Prof Geach explained: “This discovery gives us new clues as to how galactic-scale magnetic fields are formed.”

Researchers suggest that observing a fully developed magnetic field this early in the history of the universe indicates that magnetic fields spanning entire galaxies can form rapidly while young galaxies are still growing.

Co-author and ESO astronomer Rob Ivison says that the discovery opens up “a new window onto the inner workings of galaxies, because the magnetic fields are linked to the material that is forming new stars”.

To make the finding, researchers searched for light emitted by dust grains in a distant galaxy, 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 polarised.

This means that the light waves oscillate along a preferred direction rather than randomly.

When Alma detected and mapped a polarised 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,” Prof Geach said.

Researchers hope that with this and future observations of distant magnetic fields they will be able to unravel the mysteries of how these galactic features form.