 The telescope being readied for launch | |
| Alternative names | Balloon Observations Of Millimetric Extragalactic Radiation and Geophysics |
|---|---|
| Location(s) | Antarctica |
| Website | cmb |
 Related media on Commons | |
| Part of a series on |
| Physical cosmology |
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Early universe |
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TheBOOMERanG experiment (Balloon Observations Of Millimetric Extragalactic Radiation And Geophysics) was an experiment that flew a telescope on a(high-altitude) balloon and measured thecosmic 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,[1] with similar results from the competingMAXIMA 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 overNorth America in 1997. In the two subsequent flights in 1998 and 2003 the balloon was launched fromMcMurdo Station in the Antarctic. It was carried by thePolar vortex winds in a circle around theSouth Pole, returning after two weeks. From this phenomenon the telescope took its name.
The BOOMERanG team was led byAndrew E. Lange ofCaltech and Paolo de Bernardis of theUniversity of Rome La Sapienza.[2]
The experiment usesbolometers[3] for radiation detection. These bolometers are kept at a temperature of 0.27kelvin. At this temperature the material has a very low heat capacity according to theDebye 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[3] 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.
Together with experiments like theSaskatoon 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 ofHubble's constant, the Boomerang data determined thegeometry of the Universe to be flat,[1] supporting thesupernova evidence for the existence ofdark energy. The 2003 flight of Boomerang resulted in extremely highsignal-to-noise ratio maps of the CMB temperature anisotropy, and a measurement of the polarization of theCMB.[4]
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