A team of astronomers has released the largest and most detailed map of cosmic magnetic fields ever produced, based on observations from the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia. The map, designated SPICE-RACS, covers magnetic fields throughout the universe and is nearly ten times larger than the previous largest survey from 2009.
Scope and Scale
The SPICE-RACS map was created from the Rapid ASKAP Continuum Surveys (RACS), which produced a catalog of approximately 4 million distant galaxies. Researchers analyzed polarization data from roughly 350,000 of those galaxies to measure the twisting of radio light caused by magnetic fields.
This dataset is five times larger than all previous combined observations of cosmic magnetic fields.
Methodology
Magnetic fields are invisible to direct observation. Astronomers detect them by measuring the polarization of radio light that has passed through the fields. The ASKAP telescope, consisting of 36 antennas with wide fields of view, enables rapid surveys of large sections of the sky. On the resulting 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 galaxy, with signatures from more distant regions present in the finer details.
Scientific Significance
The research team, led by Dr. Alec Thomson (CSIRO scientist at the SKA Observatory) and co-author Professor Naomi McClure-Griffiths (chief scientist of the SKA Observatory), studies how magnetism affects galactic interactions. Magnetic fields may influence the formation of galaxies, star birth, space weather, and the structure of the cosmos, similar to gravity. Approximately 99.9% of visible matter in the universe is plasma, which can be channeled by magnetism. The maps show magnetic fields from the Milky Way and the nearby Magellanic Clouds.
Publication and Data Access
The study was published in Publications of the Astronomical Society of Australia by Alec Thomson and colleagues. The SPICE-RACS data has been made publicly available for the research community.
Future Work
The Polarisation Sky Survey of the Universe's Magnetism (POSSUM) project is expected to complete observations by approximately 2030. Researchers anticipate that the POSSUM survey will provide a sharper magnetic field map and allow astronomers to study magnetic fields further back in cosmic history.