Astronomers make furthest detection ever of galaxy’s magnetic field

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomical facility comprising 66 high-precision antennas, has detected the magnetic field of a very distant galaxy.

Since the galaxy's light has taken more than 11 billion years to reach Earth, astronomers see it as it was when the Universe was just 2.5 billion years old.

Until this discovery, studies of galactic magnetic fields had always focused on relatively nearby galaxies. This finding provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way formed.

"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," says James Geach, a professor of astrophysics at the University of Hertfordshire, UK, and lead author of the study published in the journal Nature.

Using ALMA, Geach and his team discovered a fully formed magnetic field in a distant galaxy, which sports a structure similar to what is observed in nearby galaxies. While the magnetic field is about 1000 times weaker than the Earth's field, it extends over more than 16,000 light-years.

"This discovery gives us new clues as to how galactic-scale magnetic fields are formed," Geach added.

The team believes that intense star formation in the early Universe could have played a role in accelerating the development of magnetic fields. In addition, these fields can influence how later generations of stars will form.

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," said the study co-author and ESO astronomer Rob Ivison.

For this discovery, astronomers searched for light emitted by dust grains in a galaxy named 9io9. Dust grains within this galaxy, as the team says, are somewhat aligned with the galaxy's magnetic field, and due to this, they emit polarised light - light waves oscillate along a preferred direction rather than randomly.

ALMA detected and mapped a polarised signal coming from this distant galaxy, confirming the presence of a magnetic field in a very distant galaxy for the first time.

Using @almaobs 📡 – in which ESO is a partner – astronomers have made the furthest detection ever of a galaxy's magnetic fieldThis sheds new light on how the magnetic fields of galaxies like ours came to be 1/📷 ALMA (ESO/NAOJ/NRAO)/J. Geach et al. pic.twitter.com/EmPkGs1tFX

— ESO (@ESO) September 6, 2023