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Light from distant quasars -- early galaxies thatshine with tremendous brightness -- has givenresearchers a new clue to the origin of vastmagnetic fields studding today's galaxies: Theywere running strong when the universe was only athird of its present age.
Astronomers had observed that radio emissions from quasars tend to be angled, or polarized, in such a way that powerful magnetic fields must have twisted them. The greater theirdistance from Earth, the more polarized their light. But researchers didn't know whether themagnetic fields were part of the quasar or were present in galaxies encountered by quasarlight as it made its journey to our telescopes.
So a team led by astronomers from the Swiss Federal Institute of Technology (ETH Zurich) scanned more than 70 of those quasars using the European Southern Observatory's Very LargeTelescope in Chile to look for signs of galaxies hiding in front of the quasars. Specifically, theychecked for a feature called the magnesium(II) absorption line, a reduction in the intensityof light of a certain wavelength, which is a commonly used indicator that gas from a star-forming galaxy has soaked up that light.
The researchers report that light from quasars showing the magnesium(II) line was morestrongly polarized than light from other quasars in the sample. The interpretation: that lightdid indeed pass through regular galaxies and that it likely acquired its polarization in theprocess.
They estimated the age of the magnetic galaxies by measuring the red shift of theabsorption line—the observed reddening of light that occurs when galaxies move rapidly apart. The typical red shift of the inferred galaxies corresponded to an age of 5.2 billion years, study author Francesco Miniati says. Precision measurements of the cosmic microwavebackground peg today's universe at 13.7 billion years old.
According to the passage, the astronomers wanted to determine if light emitted bydistant quasars was affected by _____
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