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First stars born later than thought

Planck pinpoints end of cosmological dark ages

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12:04pm, February 9, 2015
Polarization of the cosmic microwave

FIRST LIGHT   Light from the cosmic microwave background (coloring shows temperature differences) becomes aligned along certain directions, shown as swirling patterns, as it scatters off electrons in the early universe.

The first stars in the universe came on the scene a little later than previously thought.

New results from Planck, a satellite that mapped light from the early universe, pinpoint the start of reionization, an era when starlight became powerful enough to strip electrons from hydrogen atoms throughout the universe. Stars triggered the cosmological makeover about 13.25 billion years ago, a mere 550 million years after the Big Bang, researchers report online February 5 at arXiv.org.  

Previous results from the WMAP satellite suggested that reionization began about 100 million years earlier, but galaxies from that epoch don’t seem to have enough stars to ionize hydrogen. The delayed start implied by Planck means galaxies had a little more time to build the stars that they needed to drive reionization.

From 2009 to 2013, Planck mapped the cosmic microwave background, or CMB, the first light released into the

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