The
BOOMERanG experiment (
Balloon
Observations
Of
Millimetric
Extragalactic
Radiation
and
Geophysics) measured the
cosmic microwave background radiationIn cosmology, cosmic microwave background radiation is a form of electromagnetic radiation filling the universe. With a traditional optical telescope, the space between stars and galaxies is pitch black...
of a part of the sky during three sub-orbital (
high altitudeHigh altitude balloons are unmanned balloons, usually filled with helium or hydrogen that are released into the stratosphere, generally reaching between 60,000 and 120,000 feet ....
)
balloonA balloon is an inflatable flexible bag filled with a type of gas, such as helium, hydrogen, nitrous oxide or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were sometimes made of dried animal bladders...
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 meters high, it was possible to reduce the atmospheric absorption of microwaves to a minimum.
The
BOOMERanG experiment (
Balloon
Observations
Of
Millimetric
Extragalactic
Radiation
and
Geophysics) measured the
cosmic microwave background radiationIn cosmology, cosmic microwave background radiation is a form of electromagnetic radiation filling the universe. With a traditional optical telescope, the space between stars and galaxies is pitch black...
of a part of the sky during three sub-orbital (
high altitudeHigh altitude balloons are unmanned balloons, usually filled with helium or hydrogen that are released into the stratosphere, generally reaching between 60,000 and 120,000 feet ....
)
balloonA balloon is an inflatable flexible bag filled with a type of gas, such as helium, hydrogen, nitrous oxide or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were sometimes made of dried animal bladders...
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 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 small part of the sky could be scanned.
The first was a test flight over
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
in 1997. In the two subsequent flights in 1998 and 2003 the balloon was started at the
McMurdo StationMcMurdo Station is an American Antarctic research center located on the southern tip of Ross Island on the shore of McMurdo Sound in Antarctica. It is operated by the United States through the United States Antarctic Program, a branch of the National Science Foundation...
in the Antarctic. It used the
Polar vortexA polar vortex is a persistent, large-scale cyclone located near one or both of a planet's geographical poles. On Earth, the polar vortices are located in the middle and upper troposphere and the stratosphere...
winds to circle around the
South PoleThe South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects the surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
, returning after two weeks. From this phenomenon the telescope took its name.
Instrumentation
The experiment uses
bolometerA bolometer is a device for measuring the energy of incident electromagnetic radiation. It was invented in 1878 by the American astronomer Samuel Pierpont Langley....
s for radiation detection. These bolometers are kept at a temperature of 0.27
kelvinThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
. At this temperature the material has a very low heat capacity according to the
Debye lawIn thermodynamics and solid state physics, the Debye model is a method developed by Peter Debye in 1912 for estimating the phonon contribution to the specific heat in a solid. It treats the vibrations of the atomic lattice as phonons in a box, in contrast to the Einstein model, which treats the...
, 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 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
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 constantHubble's law describes the observation in physical cosmology that the velocity at which various galaxies are receding from the Earth is proportional to their distance from us. The law was first formulated by Edwin Hubble in 1929 after nearly a decade of observations...
, 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
supernovaA supernova is a stellar explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over...
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.
External links