# BOOMERanG experiment

Part of a series on :
Physical cosmology :
Big Bang · Universe
Age of the universe
Chronology of the universe :
Early universe
Inflation · Nucleosynthesis
Backgrounds
Gravitational wave (GWB)
Microwave (CMB) · Neutrino (CNB) :
Expansion · Future
Hubble's law · Redshift
Expansion of the universe
FLRW metric · Friedmann equations
Inhomogeneous cosmology
Future of an expanding universe
Ultimate fate of the universe :
Components · Structure
Components
Lambda-CDM model
Dark energy · Dark matter
Structure
Shape of the universe
Galaxy filament · Galaxy formation
Large quasar group
Large-scale structure
Reionization · Structure formation :
Experiments
Black Hole Initiative (BHI)
BOOMERanG
Cosmic Background Explorer (COBE)
Dark Energy Survey
Planck space observatory
Sloan Digital Sky Survey (SDSS)
2dF Galaxy Redshift Survey ("2dF")
Wilkinson Microwave Anisotropy Probe (WMAP) :
Scientists
Aaronson
Alfvén
Alpher
Copernicus
de Sitter
Dicke
Ehlers
Einstein
Ellis
Friedmann
Galileo
Gamow
Guth
Hawking
Hubble
Huygens
Kepler
Lemaître
Mather
Newton
Penrose
Penzias
Rubin
Schmidt
Smoot
Suntzeff
Sunyaev
Tolman
Wilson
Zeldovich
List of cosmologists :
Subject history
Discovery of cosmic microwave background radiation
History of the Big Bang theory
Timeline of cosmological theories :
Category
Astronomy portal :
vte :
BOOMERanG experiment (Balloon Observations Of Millimetric Extragalactic Radiation And Geophysics) was an experiment that flew a telescope on a (high-altitude) balloon and measured the cosmic microwave background radiation of a part of the sky during three sub-orbital flights. It was the first experiment to make large, high-fidelity images of the CMB temperature anisotropies, and is best known for the discovery in 2000 that the geometry of the universe is close to flat, with similar results from the competing MAXIMA experiment.
By using a telescope which flew at over 42,000 meters high, it was possible to reduce the atmospheric absorption of microwaves to a minimum. This allowed massive cost reduction compared to a satellite probe, though only a tiny part of the sky could be scanned.
The first was a test flight over North America in 1997. In the two subsequent flights in 1998 and 2003 the balloon was launched from McMurdo Station in the Antarctic. It was carried by the Polar vortex winds in a circle around the South Pole, returning after two weeks. From this phenomenon the telescope took its name.
The BOOMERanG team was led by Andrew E. Lange of Caltech and Paolo de Bernardis of the University of Rome La Sapienza.

## Instrumentation

The experiment uses bolometers for radiation detection. These bolometers are kept at a temperature of 0.27 kelvin. At this temperature the material has a very low heat capacity according to the Debye law, thus incoming microwave light will cause a large temperature change, proportional to the intensity of the incoming waves, which is measured with sensitive thermometers.
An off-axis 1.3-meter primary mirror focuses the microwaves onto the focal plane, which consist of 16 horns. These horns, operating at 145 GHz, 245 GHz and 345 GHz, are arranged into 8 pixels. Only a tiny fraction of the sky can be seen concurrently, so the telescope must rotate to scan the whole field of view.

## Results

Together with experiments like the Saskatoon experiment, MAT/TOCO, MAXIMA, and others, the BOOMERanG data from 1997 and 1998 determined the angular diameter distance to the surface of last scattering with high precision. When combined with complementary data regarding the value of Hubble's constant, the Boomerang data determined the geometry of the Universe to be flat, supporting the supernova evidence for the existence of dark energy. The 2003 flight of Boomerang resulted in extremely high signal-to-noise ratio maps of the CMB temperature anisotropy, and a measurement of the polarization of the CMB.