“Roaming” Magnetic Fields Found

By | April 2, 2010

Weak magnetic fields are “roaming” across the universe, according to a new study that may have solved the mystery of where the huge magnetic fields around galaxies come from.

Galaxies such as our Milky Way have their own large-scale magnetic fields. Although these fields are weak compared to planetary fields, scientists think the galactic versions help establish rates of star formation, guide cosmic rays, and regulate the dynamics of interstellar gas.

Most scientists believe the stronger magnetic fields of today’s adult galaxies grew from weaker “seed” fields. But it’s unclear where these older fields originated.

The two leading theories: The seed fields were created by the movement of charged gas in protogalaxies, or they were produced outside of galaxies by some unseen processes in the early universe.

New observations made with NASA’s Fermi Gamma-ray Space Telescope support the idea that the seeds were there all along, even before galaxies themselves.

(Related: “Gamma Ray Telescope Finds First ‘Invisible’ Pulsar.”)

Based on Fermi’s data, “we’ve found that these weak magnetic fields should be everywhere. They should be outside the galaxies, filling the whole universe, even where there are no galaxies, no clusters, no anything,” said study co-author Andrii Neronov of the University of Geneva’s ISDC Centre for Astrophysics in Switzerland.

Since the new findings suggest magnetic fields can form outside galaxies, “perhaps those magnetic fields were created before the galaxies were formed,” Neronov said.

Sowing the Seeds for Galactic Fields

According to the theory, primordial seed fields could have been created from charged particles spit out during violent events such as supernovae.

Over time, the theory goes, a seed field could bulk up inside a galaxy, because the galaxy’s slow spin causes charged particles and gases to align along the seed’s magnetic field lines. (Related: “Earth’s Core, Magnetic Field Changing Fast, Study Says.”)

But other seed fields would remain roaming through intergalactic space—and that’s what Neronov and colleagues think they’ve found.

More precisely, the team saw a lack of very high-energy gamma rays in Fermi data on blazars, galaxies with supermassive black holes at their centers that spew jets of particles at near the speed of light. …

via “Roaming” Magnetic Fields Found.

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