BOOMERanG experiment 1147832 199544459 2008-03-20T07:21:20Z SieBot 4005189 robot Adding: [[fi:BOOMERanG-koe]] [[Image:Boomerang Telescope.jpeg|thumb|300px|right|The Telescope being readied for launch]] The '''BOOMERanG experiment''' ('''B'''alloon '''O'''bservations '''O'''f '''M'''illimetric '''E'''xtragalactic '''R'''adiation '''an'''d '''G'''eophysics) measured the [[cosmic microwave background radiation]] of a part of the sky during three sub-orbital ([[high altitude balloon|high altitude]]) [[balloon]] flights. It was the first experiment to make large, high fidelity images of the CMB temperature anisotropies. By using a telescope which flew at over 42,000 metres 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 small 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 started at the [[McMurdo Station]] in the Antarctic. It used the [[Polar vortex]] winds to circle around the [[South Pole]], returning after two weeks. From this phenomenon the telescope took its name. ==Instrumentation== The experiment uses [[bolometer]]s<ref>{{cite web | title = Instrumentation of the BOOMERranG experiment | publisher = Ted's Weblog | date = 2002-01-29 | url = http://cmb.phys.cwru.edu/kisner/b2kweblog/hardware.html | accessdate = 2007-04-06}}</ref> 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 model|Debye law]], thus incoming microwave light will cause a strong temperature change, proportional to the intensity of the incoming waves, which is measured with sensitive thermometers. A 1.2 mirror<ref>{{cite web | title = Boomerang Instrument | publisher = Caltech Observational Cosmology Group | date = 2003-06-01 | url = http://www.astro.caltech.edu/~lgg/boomerang_instr.htm | accessdate = 2007-04-06}}</ref> 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 pixel. So only a tiny fraction of the sky can be seen concurrently so the telescope has to rotate to scan the whole field of view. ==Results== [[Image:Boomerang CMB.jpeg|thumb|200px|right|CMB Anisotropy measured by BOOMERanG]] Together with experiments like Saskatoon, 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 law|Hubble's constant]], the Boomerang data determined the geometry of the Universe to be flat (see [http://xxx.arxiv.org/abs/astro-ph/9911445] and [http://xxx.arxiv.org/abs/astro-ph/0004404]) , 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. ==References== <references/> ==See also== *[[Cosmic microwave background experiments]] *[[Observational cosmology]] ==External links== *[http://boom.caltech.edu Main (Caltech) Site] *[http://cmb.phys.cwru.edu/boomerang/ Data site] *[http://stratocat.com.ar/fichas-e/1998/MCM-19981229.htm report on the 1998 flight] *[http://stratocat.com.ar/fichas-e/2003/MCM-20030121.htm report on the 2003 flight] *[http://it.arxiv.org/abs/astro-ph/0209132v1 Polarization Sensitive Bolometric Detector] {{CMB_experiments}} [[Category:Physics experiments]] [[Category:Radio astronomy]] [[cs:BOOMERanG]] [[fr:BOOMERanG]] [[fi:BOOMERanG-koe]] [[zh:毫米波段氣球觀天計畫]]