🔭 Discovery of a magnetic highway connected to a galactic structure

Invisible forces, capable of shaping entire galaxies and accelerating cosmic winds to dizzying speeds, have just been observed by astronomers in Arp 220. This merging galaxy system is located 250 million light-years away. It offers a unique view of processes that governed the Universe more than ten billion years ago, when massive galaxies were in full effervescence.

Arp 220 results from the collision of two spiral galaxies, generating star formation activity so intense that it outshines hundreds of galaxies like our own. Shrouded in thick dust clouds, it shines primarily in infrared wavelengths, and allows the study of extreme conditions similar to those that prevailed in the primordial Universe.


Thanks to the ALMA telescope array, an international team has produced the most detailed magnetic map ever made of this system. Their polarization capabilities allowed tracing the alignment of dust grains and carbon monoxide molecules with the magnetic fields. This approach revealed organized and powerful magnetic structures within the fast molecular outflows escaping from the two cores of this galactic system.

The observations show that these magnetic fields play a central role in the launching and shape of galactic winds, which reach speeds of 1.8 million kilometers per hour (approximately 1.1 million miles per hour). It was initially thought that these outflows were primarily powered by intense star formation or black hole activity. The magnetic map highlighted an almost vertical "magnetic highway," where the magnetic field actively guides the matter escaping from one of the galactic nuclei.

In the western nucleus of Arp 220, astronomers observed a well-ordered magnetic structure aligned with the bipolar outflow, indicating that the magnetic field is not passive but participates in accelerating the material. The eastern nucleus, on the other hand, exhibits a spiral magnetic pattern within a dense rotating disk. A strongly polarized dust bridge also connects the two centers, indicating that magnetic fields channel matter during the merger.

These discoveries have major implications for our understanding of the early Universe. The magnetic fields in the outflows of Arp 220 are hundreds to thousands of times more intense than those of the Milky Way, thus influencing gas motion, star formation, and how galaxies lose matter. Such organized magnetic structures were probably common in dusty and active galaxies of the past, shaping galactic evolution on a large scale.

By extending these observation techniques to other systems, scientists hope to discover similar magnetic highways across the cosmos.