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Astronomers Make Historic Discovery: Magnetic Field in Distant Galaxy Rewrites Cosmic Origins

In a groundbreaking discovery, a team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has confirmed the presence of a magnetic field in a galaxy located so far away that its light has traveled for more than 11 billion years to reach Earth. This astonishing observation, detailed in a study published today in the journal Nature, sheds new light on the early universe's magnetic structure and provides invaluable insights into the formation of magnetic fields within galaxies.

This image shows the orientation of the magnetic field in the distant 9io9 galaxy, seen here when the Universe was only 20% of its current age — the furthest ever detection of a galaxy’s magnetic field. The observations were done with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. Dust grains within 9io9 are somewhat aligned with the galaxy’s magnetic field, and due to this they emit polarized light, meaning that light waves oscillate along a preferred direction rather than randomly. ALMA detected this polarization signal, from which astronomers could work out the orientation of the magnetic field, shown here as curved lines overlaid on the ALMA image. The polarized light signal emitted by the magnetically aligned dust in 9io9 was extremely faint, representing just one percent of the total brightness of the galaxy, so astronomers used a clever trick of nature to help them obtain this result. The team was helped by the fact that 9io9, although very distant from us, had been magnified via a process known as gravitational lensing. This occurs when light from a distant galaxy, in this case 9io9, appears brighter and distorted as it is bent by the gravity of a very large object in the foreground. Credit: ALMA (ESO/NAOJ/NRAO)/J. Geach et al.
This image shows the orientation of the magnetic field in the distant 9io9 galaxy, seen here when the Universe was only 20% of its current age — the furthest ever detection of a galaxy’s magnetic field. The observations were done with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. Dust grains within 9io9 are somewhat aligned with the galaxy’s magnetic field, and due to this they emit polarized light, meaning that light waves oscillate along a preferred direction rather than randomly. ALMA detected this polarization signal, from which astronomers could work out the orientation of the magnetic field, shown here as curved lines overlaid on the ALMA image. The polarized light signal emitted by the magnetically aligned dust in 9io9 was extremely faint, representing just one percent of the total brightness of the galaxy, so astronomers used a clever trick of nature to help them obtain this result. The team was helped by the fact that 9io9, although very distant from us, had been magnified via a process known as gravitational lensing. This occurs when light from a distant galaxy, in this case 9io9, appears brighter and distorted as it is bent by the gravity of a very large object in the foreground. Credit: ALMA (ESO/NAOJ/NRAO)/J. Geach et al.

Professor James Geach, an astrophysicist at the University of Hertfordshire, UK, and the lead author of the study, explained the significance of this discovery. "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," he said. "We actually know very little about how these fields form, despite their being quite fundamental to how galaxies evolve."


Traditionally, astronomers have studied magnetic fields in galaxies close to our own Milky Way, leaving questions about the early universe's magnetic evolution unanswered. However, using ALMA, an international collaboration involving the European Southern Observatory (ESO), Geach and his team have detected a fully formed magnetic field in a distant galaxy, providing a glimpse into the universe's magnetic past.


The galaxy in question, known as 9io9, resides at a staggering distance from Earth. The light we observe from 9io9 dates back to a time when the universe was only 2.5 billion years old. Despite its immense distance, ALMA's sensitivity allowed researchers to confirm the presence of a magnetic field, which is approximately 1,000 times weaker than Earth's magnetic field and extends over more than 16,000 light-years.

"This discovery gives us new clues as to how galactic-scale magnetic fields are formed," Geach explained. The detection of a fully developed magnetic field in the early universe suggests that these fields can form rapidly during a galaxy's growth phase. The team speculates that intense star formation in the early universe might have played a pivotal role in accelerating the development of these magnetic fields, which, in turn, can influence the formation of later generations of stars.


Rob Ivison, an ESO astronomer and co-author of the study, highlighted the significance of this finding for our understanding of galaxy formation. "This 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," he said.


To make this extraordinary detection, the research team focused on the light emitted by dust grains within the distant galaxy. Galaxies are rich in dust grains, and when a magnetic field is present, these grains tend to align themselves. As a result, the emitted light becomes polarized, meaning that light waves oscillate along a preferred direction instead of randomly. When ALMA detected and mapped this polarized signal coming from 9io9, it marked the first-ever confirmation of a magnetic field in a galaxy located so far away.


Geach emphasized the unique capabilities of ALMA, stating, "No other telescope could have achieved this." With this groundbreaking discovery and the promise of future observations of distant magnetic fields, the scientific community is one step closer to unraveling the mystery of how these fundamental features of galaxies come into existence. The universe's magnetic secrets are slowly but surely being unveiled, providing a deeper understanding of our cosmic origins.

Journal Information: James Geach, Polarized thermal emission from dust in a galaxy at redshift 2.6, Nature (2023). DOI: 10.1038/s41586-023-06346-4. www.nature.com/articles/s41586-023-06346-4
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