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
The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...
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
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
in 1997. In the two subsequent flights in 1998 and 2003 the balloon was launched from
McMurdo Station
McMurdo Station is an American Antarctic research station on the southern tip of Ross Island. It is operated by the United States through the United States Antarctic Program (USAP), a branch of the National Science Foundation. The station is ...
in the Antarctic. It was carried by the
Polar vortex winds in a circle around the
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the point in the Southern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True South Pole to distinguish ...
, returning after two weeks. From this phenomenon the telescope took its name.
The BOOMERanG team was led by
Andrew E. Lange of
Caltech
The California Institute of Technology (branded as Caltech) is a private university, private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small g ...
and Paolo de Bernardis of the
University of Rome La Sapienza
The Sapienza University of Rome (), formally the Università degli Studi di Roma "La Sapienza", abbreviated simply as Sapienza ('Wisdom'), is a Public university, public research university located in Rome, Italy. It was founded in 1303 and is ...
.
Instrumentation
The experiment uses
bolometer
A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley.
Principle of operation
A bolometer ...
s
for radiation detection. These bolometers are kept at a temperature of 0.27
kelvin
The kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K. By de ...
. 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
A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...
evidence for the existence of
dark energy
In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
. The 2003 flight of Boomerang resulted in extremely high
signal-to-noise ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...
maps of the CMB temperature anisotropy, and a measurement of the polarization of the
CMB.
See also
*
BESS (experiment)
References
External links
report on the 1998 flightPolarization Sensitive Bolometric Detector
{{CMB_experiments
Cosmic microwave background experiments
Balloon-borne telescopes
Astronomical experiments in the Antarctic