BICEP2 and Planck Joint Study: Gravitational waves remain elusive
The BICEP telescope at the South Pole.
A new joint analysis of data from two South Pole-based experiments--the BICEP2 telescope and the Keck Array, both supported by the National Science Foundation--and the European Space Agency's Planck satellite, has found no conclusive evidence of primordial gravitational waves, despite earlier reports of a possible detection.
In early 2014, the BICEP2 team presented results based on observations of the polarized Cosmic Microwave Background (CMB), the legacy of light emitted only 380,000 years after the Big Bang, performed on a patch of the sky between 2010 and 2012. The team also used some preliminary data from the Keck Array. Their study revealed a signal that had never before been detected: so-called "curly B-modes" in the polarization observed over stretches of the sky a few times larger than the size of the full moon.
The BICEP2/Keck Array team presented evidence favoring the interpretation that this signal originated in primordial gravitational waves, sparking an enormous response in the academic community and general public.
However, there is another phenomenon that can produce a similar effect: interstellar dust in the Milky Way Galaxy.
A new paper, "A Joint Analysis of BICEP2/Keck Array and Planck Data," submitted to the journal Physical Review Letters indicates that the interpretation of the earlier, much-publicized BICEP2 result as evidence for gravitational waves is no longer secure, once dust contamination is taken into account.