Galaxies much like ours harbor mysterious magnetic fields,
which turn out to build up much faster than scientists realized, a new study has
found.
By analyzing light coming from distant galaxies at a time
early in the universe's history, astronomers were able to show that these
galaxies developed magnetic fields much sooner than expected. The finding may force scientists
to rethink their understanding of how magnetic fields grow inside galaxies.
"The magnetic fields in these galaxies were very
strong, at least as strong as they are today, at a time when the age of the
universe was only one third of its current age," said researcher Francesco
Miniati of the Swiss Federal Institute of Technology. "That puts strong constraints
on the evolution of magnetic fields."
The discovery was made with the help of faraway light
sources that served to illuminate the galaxies being studied.
Miniati and his colleagues used the European Southern Observatory's
Paranal Observatory to observe the very distant bright objects, called quasars,
in both visual and radio frequency light. Quasars are the central regions of some
galaxies where supermassive black holes generate tremendous emissions across the
electromagnetic
spectrum, from radio waves to visible light and x-rays.
The radio waves the researchers observed often showed signs
of having passed through a magnetic field. It turned out, when a normal galaxy
lay between Earth and the quasar, the magnetic
field signature on the light was most strong. This told the researchers
that it was the foreground galaxies, and not the quasars, that held the
responsible magnetic fields.
"We were surprised that we could actually measure this
so cleanly, and we were surprised that these galaxies had such strong magnetic
fields early on," Miniati told SPACE.com. "This has been
suggested before, but seen convincingly only for some individual galaxies. What
we were able to show with this measurement is that all regular galaxies early
on have these kinds of strong magnetic fields."
Scientists think galactic magnetic fields start from tiny
magnetic seeds, perhaps created inside stars or quasars, and are then amplified
over time as the turbulent movement of galactic gas, stirred up by stellar
explosions, and the galaxy's rotation cause the magnetic fields to grow. This
standard picture, however, can only account for strong
magnetic fields that build up slowly over time. The new finding means
scientists must come up with an improved explanation for how magnetic fields
build up inside galaxies in the young universe such as those Miniati and his
team observed.
The researchers detailed their discovery in the July 17
issue of the journal Nature. The study was funded by the Swiss National
Science Foundation, the Natural Sciences and Engineering Council of Canada and
the U.S. Department of Energy.
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