POLARBEAR (POLARization of the Background Radiation) is a

cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...

polarization experiment located in the

Atacama Desert The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in the ...

of northern

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

in the

Antofagasta Region The Antofagasta Region ( es, Región de Antofagasta, ) is one of Chile's sixteen first-order administrative divisions. The second-largest region of Chile in area, it comprises three provinces, Antofagasta, El Loa and Tocopilla. It is bordered t ...

. The POLARBEAR experiment is mounted on the Huan Tran Telescope (HTT) at the

James Ax James Burton Ax (10 January 1937 – 11 June 2006) was an American mathematician who made groundbreaking contributions in algebra and number theory using model theory. He shared, with Simon B. Kochen, the seventh Frank Nelson Cole Prize in ...

Observatory in the Chajnantor Science Reserve. The HTT is located near the

Atacama Cosmology Telescope The Atacama Cosmology Telescope (ACT) is a cosmological millimeter-wave telescope located on Cerro Toco in the Atacama Desert in the north of Chile. ACT makes high-sensitivity, arcminute resolution, microwave-wavelength surveys of the sky in ord ...

on the slopes of

Cerro Toco Cerro Toco is a stratovolcano located in the eastern part of the Atacama desert in Chile's II Region (Antofagasta), approximately south of the border between Bolivia and Chile and SE of the Juriques and Licancabur volcanoes. It conforms the no ...

at an altitude of nearly . POLARBEAR was developed by an international collaboration which includes

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

Lawrence Berkeley National Lab Lawrence Berkeley National Laboratory (LBNL), commonly referred to as the Berkeley Lab, is a United States national laboratory that is owned by, and conducts scientific research on behalf of, the United States Department of Energy. Located in ...

University of Colorado at Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University of Colorado sys ...

University of California, San Diego The University of California, San Diego (UC San Diego or colloquially, UCSD) is a public university, public Land-grant university, land-grant research university in San Diego, California. Established in 1960 near the pre-existing Scripps Insti ...

Imperial College Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...

Astroparticle and Cosmology Laboratory The Astroparticle and Cosmology (APC) laboratory in Paris gathers researchers (experimentalists, theorists and observers) working in different areas including high-energy astrophysics, cosmology, gravitation, and neutrino physics. The institut ...

of the

University of Paris (2019) , image_name = Coat of arms of the University of Paris.svg , image_size = 150px , caption = Coat of Arms , latin_name = Universitas magistrorum et scholarium Parisiensis , motto = ''Hic et ubique terrarum'' (Latin) , mottoeng = Here and a ...

, KEK (High Energy Accelerator Research Organization),

McGill University McGill University (french: link=no, Université McGill) is an English-language public research university located in Montreal, Quebec, Canada. Founded in 1821 by royal charter granted by King George IV,Frost, Stanley Brice. ''McGill Universit ...

, and

Cardiff University , latin_name = , image_name = Shield of the University of Cardiff.svg , image_size = 150px , caption = Coat of arms of Cardiff University , motto = cy, Gwirionedd, Undod a Chytgord , mottoeng = Truth, Unity and Concord , established = 1 ...

History

The instrument was first installed at the

Combined Array for Research in Millimeter-wave Astronomy The Combined Array for Research in Millimeter-wave Astronomy (CARMA) was an astronomical instrument comprising 23 radio telescopes, dedicated in 2006. These telescopes formed an astronomical interferometer where all the signals are combined in a ...

site near

Westgard Pass Westgard Pass is a mountain pass on State Route 168 in Inyo County, California in the U.S. state of California. The pass lies at an elevation of and is located in between the White Mountains and Inyo Mountains ranges in the Basin and Range Pr ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

(USA) for an engineering run in 2010. It was then moved to its final destination in the

in September 2011. POLARBEAR saw first light on January 10, 2012, and began its first observing season in April 2012. In October 2014, POLARBEAR published a measurement of B-mode polarization at 150 GHz. These measurements focused on arcminute scale fluctuations likely sourced by gravitational lensing by intervening large-scale structure. Earlier in the year, the

BICEP2 BICEP (Background Imaging of Cosmic Extragalactic Polarization) and the Keck Array are a series of cosmic microwave background (CMB) experiments. They aim to measure the polarization of the CMB; in particular, measuring the ''B''-mode of the CMB ...

project published related measurements of degree-scale B-mode polarization, possibly sourced by

primordial gravitational wave In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space ...

s from

cosmic inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from seconds after the conjectured Big Bang singularity ...

, but they could not rule out

cosmic dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

as a cause. POLARBEAR's published measurements focused on a small but clean patch of the sky where galactic foregrounds should be subdominant to gravitational lensing B-modes. The POLARBEAR team was able to report that the measured B-mode polarization was of cosmic origin at a 97.2% confidence level by focusing their observing time on this small patch where they are highly sensitive to arcminute anisotropies. However, this observing strategy is insensitive to the larger degree-scale inflationary B-modes that BICEP2 and Keck Array have searched for.

References

External links

POLARBEAR website

UCSD Cosmology website
{{DEFAULTSORT:POLARBEAR Cosmic microwave background experiments

History

See also

References

External links