BICEP2 was the second generation BICEP (Background Imaging of Cosmic Extragalactic Polarization) instrument for astronomy located at Earth's south pole. Featuring a greatly improved focal plane transition edge sensor (TES) bolometer array of 512 sensors (256 pixels) operating at 150 GHz, this 26 cm aperture telescope replaced the BICEP1 instrument, and observed from 2010 to 2012.
Reports stated in March 2014 that BICEP have detected B-modes from gravitational waves in the early universe (called primordial gravitational waves). An announcement was made on 17 March 2014 from the Harvard–Smithsonian Center for Astrophysics announcing that BICEP2 had detected B-modes at the level of r = 0.20+0.07
−0.05, disfavouring the null hypothesis (r = 0) at the level of 7 sigma (5.9σ after foreground subtraction). However, on 19 June 2014, lowered confidence in confirming the cosmic inflation findings was reported.
The BICEP and Keck Array series of experiments began at the California Institute of Technology in 2002. In collaboration with the Jet Propulsion Laboratory, physicists Andrew Lange, Jamie Bock, Brian Keating, and William Holzapfel began the construction of the BICEP1 telescope which deployed to the Amundsen-Scott South Pole Station in 2005 for a three-season observing run. Immediately after deployment of BICEP1, the team, which now included Caltech postdoctoral fellows John Kovac and Chao-Lin Kuo, among others, began work on BICEP2. The telescope remained the same, but new detectors were inserted into BICEP2 using a completely different technology: a printed circuit board on the focal plane that could filter, process, image, and measure radiation from the cosmic microwave background. BICEP2 was deployed to the South Pole in 2009 to begin its three-season observing run which yielded the detection of B-mode polarization in the cosmic microwave background.
The results were released in March 2014 by the four co-principal investigators of BICEP2: John M. Kovac of the Harvard-Smithsonian Center for Astrophysics; Chao-Lin Kuo of Stanford University; Jamie Bock of the California Institute of Technology; and Clem Pryke of the University of Minnesota.
Alternative interpretation of results
On June 5, 2014 at a conference of the American Astronomical Society, astronomer David Spergel argued that the B-mode polarization detected by BICEP2 could instead be the result of light scattering off dust between the stars in our Milky Way galaxy.
|BICEP||2006||2008||100 GHz||0.93°||50 (25)|||
|150 GHz||0.60°||48 (24)|||
|BICEP2||2010||2012||150 GHz||0.52°||500 (250)|||
|Keck Array||2011||2011||150 GHz||0.52°||1488 (744)|||
|BICEP3||2013||—||95 GHz||0.37°||2560 (1280)|||
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