Physicists announced in 2014 that they had discovered a signal thought to be caused by gravitational waves traveling through the early Universe. Astronomers using the Bicep2 observatory near the South Pole announced last year they found primordial gravitational waves, but new analysis reveals that signal may have been caused by a band of dust.
When the Bicep2 results were announced last year, many observers hailed the news as one of the most-important scientific breakthroughs of the last 100 years. The oldest light in the Universe is the cosmic microwave background (CMB), which was formed around 380,000 years after the Big Bang.
Astronomers in the Bicep2 project believed that signals they recovered were ripples caused by warping of space-time in the first second of the early Universe. Such a finding would have provided substantial evidence to support the idea of cosmic inflation - a hypothesis that the Universe expanded at many times the speed of light for a small fraction of a second.
The Bicep2 team has been sharing data and ideas with the Planck collaboration of Europe, attempting to understand what other conditions may have resulted in the data received by the team at the South Pole. A press release made public by the European Space Agency (ESA) has announced that the 2014 findings are now believed to be in error.
Astrophysicists believe that if inflation occurred, it would have polarized the light that we see today as the CMB. Polarized light is simply the preferential vibration of photons in one direction or another. Modern 3D movies with clear glasses utilize this property of light to allow just one of two projected frames to pass through each eye. The microwave energy in the CMB is, indeed, polarized. Different astronomical processes result in curly (B-mode) as well as circular and radial (E-mode) polarizations. The curly polarizations are the ones that interest astronomers searching for evidence of inflation in the early Universe.
"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 polarisation of the CMB, which itself only represents only a feeble few percent of the total light," Jan Tauber, ESA's project scientist for Planck, said.
The Bicep2 team reported finding curly B-mode polarizations in the CMB, recorded over a patch of sky a few times larger than a full Moon. New analysis of the data reveals the signal may have been caused by another source - dust clouds within our own Milky Way galaxy. Although this new research does not disprove the earlier finding, it makes it less likely the conclusions of the Bicep2 team were correct.
"The sad thing is that the more data you add in, the more the gravitational wave signal seems to fade. But it's possible they're homing in on a signal, just at a lower intensity than originally thought. This search is far from over," Andrew Pontzen of the University College London said.