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.

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.

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