Galaxies

Lasers Mimic Help Explain Cosmic Magnetic Fields

According to scientists powerful lasers that mimic the effects of supernovas are now helping reveal how the magnetic fields of galaxies may have formed in the early universe. Nearly all galaxies, including our own Milky Way, have magnetic fields, ones that might affect how fast stars are born. However, where these fields come from has been a mystery. The standard model for how these fields form is that tiny magnetic fields, which existed before galaxies evolved, served as cosmic “seeds” that were amplified over time by turbulence in the intergalactic medium. Still, it remains uncertain how these seed magnetic fields arose. One notion is that they were generated by the so-called “Biermann battery effect”. To see if seed magnetic fields could form via this effect, scientists experimented with high-power lasers at the LULI laboratory in Paris to recreate extreme conditions seen in outer space. The green lasers were used to blast a carbon rod just 500 microns thick, about five times thicker than a human hair, delivering more energy on its surface in an instant than Earth would receive from sunlight for that same instant.The way the carbon rod flexes in response to this blast generates a shock wave within the low-pressure helium gas the rod is immersed in. This shock wave produces eddies that could in principle create magnetic fields. The researchers successfully generated magnetic fields using the lasers. If ramped up, they calculate that turbulence within the intergalactic medium could on time scales of about 700 million years amplify seed fields to galactic proportions, supporting current theories of how galactic magnetic fields arise.
source:www.space.com

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