Chuck Bednar for redOrbit.com – Your Universe Online
Reports published last year claiming to have detected evidence of gravitational waves emitted immediately following the Big Bang were inaccurate, new analysis of the data has revealed.
Last March, researchers at the Harvard-Smithsonian Center for Astrophysics announced in a news conference that an experiment called BICEP2 had revealed that a telescope at the South Pole had detected the waves while scanning the background radiation of the universe.
They said that the light had apparently become polarized by gravitational waves emitted in the initial moment after the explosion that caused the universe to expand. Their findings appeared to be evidence of the theory of cosmic inflation, which asserts that the waves made ripples in the cosmic microwave background radiation and helps explain the size and structure of the universe.
Shortly after their announcement, however, other researchers cast doubts on their findings, noting that the signal they detected could have been generated by dust within our galaxy. So the Harvard team joined forces with the European Space Agency to further investigate the matter, and sure enough, that’s exactly what happened, according to BBC News reports.
“Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves,” the ESA confirmed in a statement.
A paper detailing the results of their analysis has been submitted to the peer-reviewed journal Physical Review Letters, but the BBC said that the conclusion was “not a major surprise,” since the team itself had already publically stated that their confidence in their discovery had waned.
As the National Science Foundation (NSF) explained in a press release, the initial findings were based on observations of the polarized Cosmic Microwave Background (CMB) in a patch of sky between 2010 and 2012. The data collected revealed a signal that was previously undetected: “curly B-modes” observed in stretches of the sky several times larger than a full moon.
While the BICEP2 team released evidence suggesting that the signal originated in primordial gravitational waves, the NSF noted that interstellar dust found in the Milky Way can produce a similar affect. The new paper concluded that the interpretation of the earlier data as evidence of gravitational waves was “no longer secure” once possible dust contamination is accounted for.
“Searching for this unique record of the very early universe is as difficult as it is exciting, since this subtle signal is hidden in the polarization of the CMB, which itself only represents only a feeble few percent of the total light,” said Jan Tauber, ESA’s project scientist for Planck.
“When we first detected this signal in our data, we relied on models for Galactic dust emission that were available at the time,” added John Kovac, a BICEP2 principal investigator at Harvard. “These seemed to indicate that the region of the sky chosen for our observations had dust polarization much lower than the detected signal.”
Planck observed the sky in nine microwave and sub-millimeter frequency channels, seven of which were also equipped with polarization-sensitive detectors. While the BICEP2 team selected a region of the sky where they believed foreground dust emissions would be low, the new analysis reveals that it could have been far higher than previously believed.
“This joint work has shown that the detection of primordial B-modes is no longer robust once the emission from Galactic dust is removed,” said Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institute d’Astrophysique Spatiale in France. “So, unfortunately, we have not been able to confirm that the signal is an imprint of cosmic inflation.”
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