The Cosmic Background Imager (or CBI) was a 13-element
interferometer
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...
perched at an elevation of 5,080 metres (16,700 feet) at
Llano de Chajnantor Observatory
Llano de Chajnantor Observatory is the name for a group of astronomical observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Region approximately 50 kil ...
in the
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 ...
an
Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
. It started operations in 1999 to study the
cosmic microwave background radiation
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 ...
and ran until 2008.
CBI conducted measurements at frequencies between 26 and 36
GHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
in ten bands of 1 GHz
bandwidth
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
. It had a resolution of better than 1/10 of a degree. (In comparison, the pioneering
COBE satellite, which produced the first detection of fluctuations in the microwave background in 1992, had a resolution of about 7 degrees.) Among the key findings of the CBI is the fact that fluctuations which have a small size on the sky are weaker than fluctuations which have a large size on the sky, which confirmed earlier theoretical predictions. More technically, CBI was the first experiment to detect intrinsic anisotropy in the
microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...
background on mass scales of galaxy clusters; it provided the first detection of the
Silk damping tail; it found a hint of excess power at high-l multipoles (CBI-excess) than expected from the
ΛCDM
The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parameterization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda (Greek Λ) associated with d ...
model; and it detected fluctuations in the
polarization of the microwave background obtaining the first detailed E-mode polarization spectrum providing evidence that it is out of phase with the total intensity mode spectrum.
The CBI was built at the
California Institute of Technology
The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
, and employed sensitive radio amplifiers from the
National Radio Astronomy Observatory
The National Radio Astronomy Observatory (NRAO) is a federally funded research and development center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc. for the purpose of radio a ...
; two similar experiments are the
Very Small Array
The Very Small Array (VSA) was a 14-element interferometric radio telescope operating between 26 and 36 GHz that is used to study the cosmic microwave background radiation. It was a collaboration between the University of Cambridge, Univers ...
, operated on the island of
Tenerife
Tenerife (; ; formerly spelled ''Teneriffe'') is the largest and most populous island of the Canary Islands. It is home to 43% of the total population of the archipelago. With a land area of and a population of 978,100 inhabitants as of Janu ...
, and the
Degree Angular Scale Interferometer
The Degree Angular Scale Interferometer (DASI) was a telescope installed at the U.S. National Science Foundation's Amundsen–Scott South Pole Station in Antarctica. It was a 13-element interferometer operating between 26 and 36 GHz (Ka band ...
, operated in
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
. Both of these experiments used radio interferometry to measure CMB fluctuations at lower resolution over larger areas of the sky. Another experiment operated from Antarctica, the
Arcminute Cosmology Bolometer Array Receiver
ACBAR was an experiment to measure the anisotropy of the Cosmic microwave background. It was active 2000-2008.
The ACBAR 145 GHz measurements were the most precise high multipole measurements of the CMB at the time.
See also
*Cosmic microwa ...
, used total power (bolometric) detection and a single antenna at higher frequency and similar
angular resolution
Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. ...
to obtain results comparable to the CBI. The confluence of these and other CMB experiments employing different measurement techniques in recent years is a great triumph of observational cosmology.
CBI was a collaboration among a number of institutions in the US and Europe. It still closely collaborates with Chilean institutions
Universidad de Chile
The University of Chile ( es, Universidad de Chile) is a public research university in Santiago, Chile. It was founded on November 19, 1842, and inaugurated on September 17, 1843. and
Universidad de Concepción
Universidad (Spanish for "university") may refer to:
Places
* Universidad, San Juan, Puerto Rico
* Universidad (Madrid)
Football clubs
* Universidad SC, a Guatemalan football club that represents the Universidad de San Carlos de Guatemala
...
through the Chajnantor Observatory.
In 2006, new 1.4 m antennas replaced the old 0.9 m dishes for more high-resolution studies in total intensity mode. During this stage, CBI was called CBI-2.
In June 2008, CBI-2 stopped the observations and the 13-antenna instrument was removed from its mount. The new
QUIET telescope
Quiet may refer to:
* Silence, a relative or total lack of sound
In music
* The Quiett (born 1985), South Korean rapper
* ''Quiet'' (album), a 1996 John Scofield album
* "Quiet", a song by Lights, from her album '' The Listening'' (2009)
* "Qui ...
instrument was installed in August 2008 on the CBI mount, replacing CBI-2 .
See also
*
List of telescope types
The following are lists of devices categorized as types of telescopes or devices associated with telescopes. They are broken into major classifications with many variations due to professional, amateur, and commercial sub-types. Telescopes can be ...
*
Very Small Array
The Very Small Array (VSA) was a 14-element interferometric radio telescope operating between 26 and 36 GHz that is used to study the cosmic microwave background radiation. It was a collaboration between the University of Cambridge, Univers ...
*
Wilkinson Microwave Anisotropy Probe
The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP and Explorer 80), was a NASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic mic ...
*
Degree Angular Scale Interferometer
The Degree Angular Scale Interferometer (DASI) was a telescope installed at the U.S. National Science Foundation's Amundsen–Scott South Pole Station in Antarctica. It was a 13-element interferometer operating between 26 and 36 GHz (Ka band ...
External links
Caltech Chajnantor ObservatoryOfficial Web Page
{{Portal bar, Chile, Astronomy, Stars, Spaceflight, Outer space, Solar System
Radio telescopes
Astronomical observatories in Chile
Interferometric telescopes
Buildings and structures in Antofagasta Region
Cosmic microwave background experiments
Science and technology in Chile