Magnetic seeds

The vast magnetic fields astronomers observe across galaxy clusters and galaxies themselves, but cannot yet explain, may have been seeded by lesser fields that formed in the very early Universe, even before the first atoms existed. The suggestion could polarise cosmologists who are already divided between conflicting theories.

Kiyotomo Ichiki of the National Astronomical Observatory of Japan, in Mitaka, Tokyo and the Kavli Institute for Cosmological Physics, at the University of Chicago, Illinois, and colleagues there and in the Department of Physics, at Princeton University, New Jersey, Toshiba’s Corporate Research and Development Center, in Kawasaki, and the Department of Astronomy, at the University of Tokyo, suggest that seed magnetic fields were created from electric currents that arose from the scatter of charged protons bouncing away from electrons in a very early and hot Universe.

Kiyotomo Ichiki

The origin of such magnetic fields with large coherent length is still one of the biggest mysteries in cosmology, Ichiki has said. Conventional models such as the Biermann battery effect explain the magnetic fields as being generated from an electric current driven by the rotation of the system and can explain the amplification of small-scale fields in stars and supernovae, but not on the cosmological scale. Other theories point to direct generation in the early Universe, several 100 millions years after the Big Bang, however, there is little observational evidence. On the other hand, the researchers suggest, cosmological mechanisms based on inflation have no difficulty in accounting for the length of coherence…because of the expansion of the Universe.

The researchers explain that the existence of these seed magnetic fields provides a strong enough effect to counteract the dilution effect caused by the rapidly expanding Universe. Indeed, this may have been quite strong enough to affect primordial star formation in the early Universe, Ichiki and colleagues say. What makes this new magnetic explanation attractive is that it requires the researchers to make no assumptions about initial conditions as the vast magnetic fields arise irrespective and could help explain the lumpiness of the Universe we observe today.

Galaxies (Credit: NSSDC/NASA)

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