Scientists involved in the POLARBEAR consortium have investigated the subtle characteristics in the cosmic microwave background radiation polarization. The paper, published in the Astrophysical Journal, led by Adrian Lee, University of California, Berkeley physicist, has described the first isolation of a “B-mode”.
These findings will allow scientists to map large-scale structures of the universe, determine the masses of neutrinos as well as uncover some of the mysteries still revolving around dark matter and dark energy. Their isolation of the “B-mode” produced by gravitational lensing in cosmic microwave background radiation polarization is the first step.
A microwave’s electric field has a particular orientation- this is called polarization, which can be twisted into what is called a “B-mode” pattern when light passes through the gravitational fields of massive objects (such as galaxy clusters).
“We made the first demonstration that you can isolate a pure gravitational lensing B-mode on the sky. Also, we have shown you can measure the basic signal that will enable very sensitive searches for neutrino mass and the evolution of dark energy.”
said Lee, POLARBEAR’s prime investigator and UC Berkley professor of physics.
The POLARBEAR team uses microwave detectors which are mounted on the Huan Tran Telescope in the Atacama Desert. More than 70 scientists are included in POLARBEAR’s team, which rivals the BICEP2 experiment (Background Imaging of Cosmic Extragalactic Polarization) team- the latter surprised POLARBEAR by announcing that they had found the holy grail of microwave background research. According to BICEP2, the signature of cosmic inflation had been found in the polarization pattern of microwave radiation.
Any subsequent observations (such as those announced by the Planck Satellite) have only suggested that BICEP2 had not detected what they had claimed. And although POLARBEAR might either confirm or infirm BICEP2’s results, the team has only focused on interpreting polarization patterns in order to map how matter was distributed during the universe’s inflationary period (380,000 after the Big Bang).
Their aim is to determine the moment when dark energy (which contributes to the acceleration of the universe’s expansion) began dominating gravity, which slowed the expansion through most of the cosmic history.
Lee explained that POLARBEAR is using a different approach than BICEP2 and that they aim to measure light polarization dating from an era 380,000 years after the Big Bang:
“when the early universe was a high-energy laboratory, a lot hotter and denser than now, with an energy density a trillion times higher than what they are producing at the CERN collider.”
Lee said, trying to explain the team’s technique.
“Think of it like this: the photons are bouncing off the electrons, and there is basically a last kiss, they touch the last electron and then they go for 14 billion years until they get to telescopes on the ground. That last kiss is polarizing.”