Cosmic microwave background radiation

In cosmology, the cosmic microwave background radiation (CMB) is a form of electromagnetic radiation discovered in 1964 that radiates throughout the universe in the microwave range.

Experiments

Of these experiments, the Cosmic Background Explorer (COBE) satellite that was flown in 1989-1996 is probably the most famous and which made the first detection of the large scale anisotropies (other than the dipole). Inspired by the COBE results, a series of ground and balloon-based experiments measured CMB anisotropies on smaller angular scales over the next decade. The primary goal of these experiments was to measure the scale of the first acoustic peak, which COBE did not have sufficient resolution to resolve. These measurements were able to rule out cosmic strings as a theory of cosmic structure formation, and suggested cosmic inflation was the right theory. The first peak was measured with increasing sensitivity and by 2000 the BOOMERanG experiment reported that the highest power fluctions occur at one degree scales. Together with other cosmological data, these results implied that the geometry of the Universe is flat. A number of ground-based interferometers provided measurements of the fluctuations with higher accuracy over the next three years, including the Very Small Array and the Cosmic Background Imager. In fact, the Cosmic Background Imager has made the first detection of the CMB polarization.

Related Topics:
COBE - 1989 - 1996 - Cosmic strings - Cosmic inflation - BOOMERanG experiment - Flat - Interferometers - Very Small Array - Cosmic Background Imager

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In June 2001, NASA launched a second CBR space mission, WMAP, to make much more accurate measurements of the large scale anisotropies over the full sky. Results from this mission disclosed in 2003 provided a detailed measurement of the angular power spectrum down to degree scales, tightly constraining various cosmological parameters. The results are broadly consistent with those expected from cosmic inflation as well as various other competing theories, and are available in detail at NASA's data center for Cosmic Microwave Background (CMB) (see links below). Although WMAP provided very accurate measurements of the large angular-scale fluctuations in the CMB (structures about as large in the sky as the moon), it did not have the angular resolution to measure the small scale fluctuations which had been observed using previous ground-based interferometers.

Related Topics:
June 2001 - NASA - WMAP - Cosmic inflation - Interferometers

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A third space mission, the Planck Surveyor, is to be launched in 2007. Planck employs both HEMT radiometers as well as bolometer technology and will measure the CMB on smaller scales than WMAP. Unlike the previous two space missions, Planck is a collaboration between NASA and ESA (the European Space Agency). Its detectors got a trial run at the Antarctic Viper telescope as ACBAR (Arcminute Cosmology Bolometer Array Receiver) experiment – which has produced the most precise measurements at small angular scales to date – and at the Archeops balloon telescope.

Related Topics:
Planck Surveyor - HEMT - Bolometer - ESA - Viper telescope - ACBAR - Arcminute Cosmology Bolometer Array Receiver - Archeops

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Additional ground-based instruments such as the CLOVER array and South Pole Telescope in Antarctica and the Atacama Cosmology Telescope in Chile will provide additional data not available from satellite observations, possibly including B-mode polarization component.

Related Topics:
CLOVER array - South Pole Telescope - Atacama Cosmology Telescope

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List of experiments in approximate chronological order

Each experiment provided improved data quality when compared with previous experiments.

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• Cosmic Background Explorer - measured the very large scale fluctuations
• Saskatoon experiment - an experiment in Saskatchewan
• Cosmic Anisotropy Telescope - measured the very small scale fluctuations in small regions of the sky
• Maxima - measured intermediate scale fluctuations with improved precision
• BOOMERanG experiment - measured intermediate scale fluctuations with improved precision
• BEAST - A ground-based single dish CMB observatory at the University of California's White Mountain Research station.
• Archeops - measured large and intermediate scale with improved precision at the larger scales
• Cosmic Background Imager - measured the very small scale fluctuations with improved precision in small regions of the sky
• Very Small Array - measured intermediate and small scale fluctuations with improved precision in small regions of the sky
• Degree Angular Scale Interferometer - a temperature and polarization telescope at the South Pole
• Arcminute Cosmology Bolometer Array Receiver - measured intermediate and small scale fluctuations with improved precision
• Wilkinson Microwave Anisotropy Probe - measured intermediate and large scale fluctuations with improved precision
• QuaD (ongoing) - measured intermediate scale polarization with improved precision (South Pole).
• BICEP (dec 2005) - measured large scale polarization with improved precision (South Pole).
• Atacama Pathfinder EXperiment /SZ - (2005/2006) new telescope, prototype of ALMA, will be used partly to measure small scale fluctuations
• Atacama Cosmology Telescope - (2006) new telescope for measuring the small scale fluctuations being built in the Atacama Desert in Chile
• South Pole Telescope - (2006) a new telescope for measuring the small scale fluctuations and polarization, located at the South Pole
• SPIDER (2009?) - balloon-borne, will measure very large scale polarization.
• CLOVER - (2008?) - improved precision for small scale fluctuations and B-mode polarization measurements
• Planck - (2009?) - will give improved precision and polarization data at all scales