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Early galaxy's magnetism surprises scientists

If there had been a gargantuan refrigerator in the early universe, it might have been plastered with little magnetic galaxies.
/ Source: Discovery Channel

If there had been a gargantuan refrigerator in the early universe, it might have been plastered with little magnetic galaxies.

That's because the first direct measurement of an early galaxy's magnetic field has surprised astronomers by revealing a field 10 to 15 times stronger than that of our own Milky Way galaxy.

"It's enormous," said Arthur Wolfe, of San Diego's Center for Astrophysics and Space Sciences and a professor of physics at the University of California. "That was a big shock."

What makes it a surprise is that early galaxies have been thought of as hot beds of star formation. But strong galactic magnetic fields — which are generated by cool gases that would normally coalesce to form stars — tend to push matter apart and stave off the birth of stars.

"The theory is that it should be weaker, not stronger," Wolfe told Discovery News. Wolfe is the lead author of a paper on the discovery appearing in the Oct. 2 issue of the journal Nature.

The very young "proto-galaxy" in question, known as DLA-3C286, is 6.5 billion light-years away, which means the radio waves collected for the study are just as old. The galaxy was chosen for the research because its radio band emissions, a form of light, have a very strong and distinct dead zone, or "absorption line," at the wavelength of 21 cm — which is the fingerprint of hydrogen gas.

By aiming the Robert C. Byrd Green Bank Telescope at the young galaxy and applying a new technique, the team was able to detect a split in that hydrogen line which matches the effect of a strong magnetic field on hydrogen gas.

"It's a very large magnetic field strength for a galaxy by any standard," confirmed astronomer and galactic magnetism researcher Ellen Zweibel of the University of Wisconsin-Madison.

That said, the discovery creates a conundrum, said Zweibel. Current galactic evolution theory predicts that galaxies should start with weak fields, grow stars and structure, and gradually get stronger magnetic fields thereafter. So finding one that starts life strong is a little hard to explain.

One possibility is that DLA-3C286 is not one galaxy but two caught in the act of colliding, said Wolfe. When galaxies collide their gases mix in ways that can generate much stronger magnetic fields — for a short time.

Unfortunately, said Wolfe, the chance of catching galaxies in the act of colliding is about one in 100. So either his team got very lucky, or something else is going on.

To find out, Wolfe is working on getting some observing time on another telescope to look at a wispy arm of material coming off DLA-3C286. It might contain clues to what is happening there.