The largest magnetic map of the Universe ever produced – five times larger than all previous efforts combined – marks the beginning of a new generation of research into the field of intergalactic magnetism.
Magnetic fields influence how galaxies grow, how matter moves through space, and how the Universe has evolved over billions of years.
This new map, called SPICE-RACS, works on the principle that light twists as it travels through magnetic fields. It was produced with CSIRO’s ASKAP radio telescope on Wajarri Yamaji Country. Credit: CSIRO/Alec Thomson et al./Alex Cherney/Sam Moorfield
The new map was produced by an international team led by researchers at CSIRO and the SKA Observatory (SKAO).
Lead researcher Dr Alec Thomson, commissioning scientist with the SKAO and CSIRO affiliate, said that for the first time, we can investigate fine details of the material between nearby stars, and study a huge number of distant galaxies.
The paper has been accepted by Publications of the Astronomical Society of Australia, and the results are available to the scientific community on our data archive portal.
It was the advanced capabilities of our ASKAP radio telescope that enabled this research. ASKAP, located at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory on Wajarri Yamaji Country in Western Australia, is a precursor to the international SKA telescopes under construction in Australia and South Africa.
A magnetic image of this size and scale was previously out of reach, but new technologies such as ASKAP’s large field of view and unique dish rotation system, combined with the ability to process huge amounts of different data, have unlocked this new chapter of astronomical investigation.
ASKAP is used to scan the sky regularly to build highly detailed maps of the Universe’s radio signals called the Rapid ASKAP Continuum Surveys (RACS). Multiple surveys have been produced since the first record-breaking RACS completed in 2020, the fastest and largest radio sky survey ever made.
An image of rotation measures across the RACS survey area in Galactic coordinates using nearest-neighbour interpolation using diverging colour map and a linear scale to highlight different features of the RM sky. From Thomson et al. 2026
This new map, called SPICE-RACS, works on the principle that light twists as it travels through magnetic fields. By measuring how twisted the light detected by ASKAP was, Dr Thomson and his team could show where magnetic fields were located and their relative strength.
They collected rotation measures from every galaxy detected in RACS (nearly 4 million galaxies) and reprocessed this original data from ASKAP to retrieve the full picture.
Professor Naomi McClure-Griffiths, SKAO’s Chief Scientist and a member of the research team, is a leader in the study of the Universe’s magnetic fields. She said SPICE-RACS is a huge leap forward, as for the past 20 years, astronomers have been working with the same data set that did not even cover the Southern Sky.
It’s not known how magnetic fields came to exist in the Universe, but they are everywhere. The Earth itself has a magnetic field that has helped us navigate the oceans. Extremely dense objects like neutron stars and black holes can have fields that are thousands of billions times stronger than the Earth’s magnetic field. In the space between stars there are magnetic fields a million times weaker than that of the Earth.
With this map, many of the unknowns and outstanding questions may finally be answered.
Our CSIRO’s data access portal, where these maps are kept, is a resource for everyone. The data is accessible and available to be used for something unique in your own work or to replicate something tested already – an important part of the scientific process.
The data portal, accessed via data.csiro.au, provides access to research data, software and other digital assets published by CSIRO across a range of disciplines, including astronomy.
The data for this project is already being used by many research teams to produce new insights and this is only just the beginning. The international team, called the Polarisation Sky Survey of the Universe’s Magnetism (POSSUM) collaboration, are already publishing science results and will continue to produce even better maps over the next few years with ASKAP.
When new telescopes such as the SKA telescopes begin early operations later this decade, these will enable astronomers to chart details of the cosmic web in finer detail and help explain the origin of magnetic fields in the Universe.