A new cosmic map, called SPICE-RACS, is the largest-ever chart of magnetic fields in the universe, offering a revolutionary view of how these invisible forces shape the cosmos.
A team of astronomers led by researchers from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the SKA Observatory (SKAO) has released the most extensive map of magnetic fields in the universe. The map, named SPICE-RACS, is based on observations from the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope and is several times larger than previous efforts.
Key Data and Methodology
The map was created using data from the Rapid ASKAP Continuum Surveys (RACS). The team analyzed signals from nearly four million galaxies, with a subset of approximately 350,000 galaxies used for precise magnetic field measurements.
This dataset is reported to be five times larger than all previous combined observations and nearly ten times larger than the previous largest map, which was produced in 2009.
The map measures the rotation of light as it travels through magnetic fields, a phenomenon known as polarisation or rotation measure. This data allows scientists to infer the location, strength, and direction of magnetic fields. On the map, red colors indicate magnetic fields pointing toward Earth, while blue indicates fields pointing away. Most of the visible structure originates from the Milky Way's magnetic field, with finer details from more distant regions, including the Magellanic Clouds.
Observational Location and Technology
Data was collected using the ASKAP radio telescope, located at the CSIRO Murchison Radio-astronomy Observatory (Inyarrimanha Ilgari Bundara) in Western Australia on Wajarri Yamaji Country. The telescope consists of 36 antennas and can observe large sections of the sky simultaneously. The Murchison Widefield Array, another radio telescope at the same site, was also used to process data at a rate of 100 trillion bits per second.
Publication and Data Access
The research has been accepted for publication in Publications of the Astronomical Society of Australia. The lead author is Dr. Alec Thomson, a CSIRO scientist at the SKA Observatory. Co-authors include Professor Naomi McClure-Griffiths, Chief Scientist of the SKA Observatory, and Dr. Tim Galvin, a CSIRO astronomer. The data is publicly available for scientific research via the CSIRO data access portal.
Scientific Context and Future Work
The origin and evolution of cosmic magnetic fields are not fully understood. Magnetic fields are thought to influence galaxy formation, star formation, and the movement of matter in the universe. Approximately 99.9% of visible matter in the universe is plasma, which can be channeled by magnetic fields. Previous magnetic field maps did not cover the southern sky.
The map is part of the Polarisation Sky Survey of the Universe's Magnetism (POSSUM) collaboration. The POSSUM project is expected to complete observations by 2030, which may produce a sharper map and allow astronomers to study magnetic fields further back in cosmic history. The SKA telescopes, currently under construction in Australia and South Africa, are expected to begin early operations later this decade, enabling finer detail studies of cosmic magnetic fields.