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‘Cosmic dawn’ took place 560 million years after the Big Bang

Image above: A visualisation of the polarisation of the Cosmic Microwave Background as detected by ESA’s Planck satellite on a small patch of the sky measuring 20º across. Image courtesy of the European Space Agency

The Universe forged its first stars 140 million years later than once thought, the Planck satellite has revealed.

Data from past experiments, muddied by dust interference, has suggested the first stars were born about 420 million years after the Big Bang. But Planck’s more precise measurements of the polarization of the cosmic background radiation – the remnants of the first light in the Universe – showed that the electrons and protons from the first stars began interacting with it slightly later than previously thought.

The new birth date aligns better with the rest of the Universe’s 13.8 billion-year history, including the formation of the first galaxies. “There was a puzzle, and the puzzle is partly resolved by what Planck has showed,” says J. Richard Bond (University of Toronto), leader of Planck’s Canadian team and director of CIFAR’s program in Cosmology & Gravity.

The Planck team also includes CIFAR Senior Fellow Barth Netterfield (University of Toronto), CIFAR Associate Fellow George Efstathiou (University of Cambridge) and Advisor Simon White (Max Planck Institute for Astrophysics).

Another of the papers in the new set released by Planck researchers, written collaboratively with researchers on the BICEP2 South Pole telescope, confirms that BICEP2 did not detect gravitational waves from inflation last year, as previously thought. Instead of detecting the ripples in space time caused by a rapid expansion of the Universe instants after the Big Bang, the instrument was confused by cosmic dust.

“There may still be a primordial signal for gravity waves but it’s still too buried by dust to say,” Bond says. Netterfield and CIFAR Senior Fellow Mark Halpern (University of British Columbia) are collaborators on BICEP2.

Overall, the new release of scientific papers by the Planck collaboration fleshes out a portrait of the early Universe that confirms the standard model of cosmology with more precision than ever before, from the Big Bang and inflation to a long, slow process of cooling, expansion and formation of celestial bodies.

It also refines detections of lensing, how gravity bends light when a mass such as a planet intervenes. “For we astronomers this advance in cosmic lensing is a huge thing, because we’re using it to better determine the nature of dark energy,” Bond says.

Lensing allowed Planck to estimate with great precision what proportion of the matter in the Universe is dark energy — 69 per cent to within 1 per cent. The data highly constrains modified theories of gravity that could mimic aspects of dark energy. Bond says. “Everything is still fitting in place for the simplest cosmological constant explanation, even if it’s an incredibly mysterious one.”

CIFAR’s program in Cosmology & Gravity has spent the last 29 years seeking no less than an explanation for everything, and its fellows are focused heavily on studying the cosmic microwave background. “The program has been intimately associated with the development on the world scene of the field of cosmic microwave background research,” Bond says.

From the first detection of temperature fluctuations in the cosmic microwave background, or anisotropies, when Stephen Hawking was a fellow of the program in the early 1990s, to the Boomerang experiment, WMAP and now Planck, Bond says there has been a rising sense of excitement within Cosmology & Gravity.

“It’s that kind of swell of experimental advance that has led to the remarkable period we are in, which people call the golden age of cosmology.”


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