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POLARBEAR Experiment
POLARBEAR experiment logo.png
Organization multiple international
Location Atacama Desert, Chile
Coordinates 22°57′30″S 67°47′10″W / 22.95833°S 67.78611°W / -22.95833; -67.78611Coordinates: 22°57′30″S 67°47′10″W / 22.95833°S 67.78611°W / -22.95833; -67.78611
Altitude 5,200 metres (17,100 ft)
Wavelength 2 mm (microwave)
Built 2010
First light 2012 (Chile)
Website Polarbear

POLARBEAR is a cosmic microwave background polarization experiment located in the Atacama Desert of northern Chile in the Antofagasta Region. The POLARBEAR experiment is mounted on the Huan Tran Telescope (HTT) at the James Ax Observatory in the Chajnantor Science Reserve. The HTT is located near the Atacama Cosmology Telescope on the slopes of Cerro Toco at an altitude of nearly 5,200 m (17,100 ft).[1][2]

POLARBEAR was developed by an international collaboration which includes University of California at Berkeley, Lawrence Berkeley National Lab, University of Colorado at Boulder, University of California at San Diego, Imperial College, Laboratoire Astroparticule et Cosmologie of the Paris Diderot University, KEK (High Energy Accelerator Research Organization), McGill University, and Cardiff University.


The instrument was first installed at the Combined Array for Research in Millimeter-wave Astronomy site near Westgard Pass in California (USA) for an engineering run in 2010. It was then moved to its final destination in the Atacama Desert in September 2011. POLARBEAR saw first light on January 10, 2012, and began its first observing season in April 2012.[3]

In October 2014, a measurement of the B-mode polarization at 150 GHz was published.[4] The findings provided evidence for primordial gravitational waves caused by cosmic inflation. Earlier in the year, the BICEP2 project had published similar measurements of the B-mode polarization, but they could not rule out cosmic dust as a cause. POLARBEAR focuses on a smaller patch of the sky and is less susceptible to dust effects. The team reported that POLARBEAR's measured B-mode polarization was of cosmological origin (and not just due to dust) at a 97.2% confidence level.[5]

See also[edit]


  1. ^ Keating, B.; Moyerman, S.; Boettger, D.; Edwards, J.; Fuller, G.; Matsuda, F.; Miller, N.; Paar, H.; Rebeiz, G. et al. (2011). "Ultra High Energy Cosmology with POLARBEAR" 1110. p. 2101. arXiv:1110.2101. Bibcode:2011arXiv1110.2101K. 
  2. ^ Lee, Adrian T.; Tran, Huan; Ade, Peter; Arnold, Kam; Borrill, Julian; Dobbs, Matt A.; Errard, Josquin; Halverson, Nils; Holzapfel, William L.; Howard, Jacob; Jaffe, Andrew; Keating, Brian; Kermish, Zigmund; Linder, Eric; Miller, Nathan; Myers, Mike; Niarchou, Anastasia; Paar, Hans; Reichardt, Christian; Spieler, Helmuth; Steinbach, Bryan; Stompor, Radek; Tucker, Carole; Quealy, Erin; Richards, Paul L.; Zahn, Oliver; Kodama, Hideo; Ioka, Kunihito (28 August 2008). "POLARBEAR: Ultra-high Energy Physics with Measurements of CMB Polarization". AIP Conference Proceedings 1040: 66. doi:10.1063/1.2981555. 
  3. ^ "First Light in Chile!". University of California Berkeley Department of Physics. Retrieved March 5, 2012. 
  4. ^ The Polarbear Collaboration (October 2014). "A Measurement of the Cosmic Microwave Background B-Mode Polarization Power Spectrum at Sub-Degree Scales with POLARBEAR" (PDF). The Astrophysical Journal. Bibcode:2014ApJ...794..171T. doi:10.1088/0004-637X/794/2/171. Retrieved November 16, 2014. 
  5. ^ "POLARBEAR project offers clues about origin of universe's cosmic growth spurt". Christian Science Monitor. October 21, 2014. 

External links[edit]