COSMOSOMAS is a circular scanning

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

experiment to investigate the

Cosmic Microwave Background 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 ...

anisotropy and diffuse emission from the

Galaxy A galaxy is a Physical system, system of stars, stellar remnants, interstellar medium, interstellar gas, cosmic dust, dust, and dark matter bound together by gravity. The word is derived from the Ancient Greek, Greek ' (), literally 'milky', ...

on angular scales from 1 to 5 degrees. It was designed and built by the

Instituto de Astrofísica de Canarias The Instituto de Astrofísica de Canarias (IAC) is an astrophysical research institute located in the Canary Islands, Spain. It was founded in 1975 at the University of La Laguna. It operates two astronomical observatories in the Canary Islands: ...

(IAC) in

Tenerife Tenerife ( ; ; formerly spelled ''Teneriffe'') is the largest and most populous island of the Canary Islands, an Autonomous communities of Spain, autonomous community of Spain. With a land area of and a population of 965,575 inhabitants as of A ...

, Spain, in 1998. Its name comes from "COSMOlogical Structures On Medium Angular Scales" referring to CMB fluctuations. This experiment grew out experience of the previous

Tenerife Experiment The Tenerife Experiment was a Cosmic Microwave Background ( CMB) experiment built by Nuffield Radio Astronomy Laboratories' team at Jodrell Bank observatory which is part of the University of Manchester in collaboration with the Instituto de Astr ...

with the need to go to smaller angular scales with greater sensitivity. The experiment consists of two instruments, COSMO15 (three channels at 12.7, 14.7 and 16.3 GHz) and COSMO11 (two hands of linear polarization at 10.9 GHz). Both instruments are based on a circular scanning sky strategy, consisting of a 60 rpm spinning flat mirror directing the sky radiation into an off-axis paraboloidal antenna, whose size is 1.8-m in the COSMO15 and 2.4-m in the COSMO11. These antennas focus the radiation on to cryogenically cooled HEMT-based receivers, both at an

operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...

of 20K (-253 C) and in the frequency range of 10–12 GHz for COSMO11, and 12–18 GHz for COSMO15. In the COSMO15 instrument, the signal is split by a set of three filters, allowing simultaneous observations at 13, 15 and 17 GHz. Thus, four 1-degree resolution sky maps complete in right ascension and covering 20 degrees in declination are obtained every day at these frequencies. The most important result to come from this experiment is the cleanest detection of " spinning dust" in the

Perseus molecular cloud The Perseus molecular cloud (Per MCld) is a nearby (~1000 ly) giant molecular cloud in the constellation of Perseus and contains over 10,000 solar masses of gas and dust covering an area of 6 by 2 degrees. Unlike the Orion molecular cloud it is ...

. These are very small dust grains which can spin thousands of million times a second. If they have an asymmetrical electrical charge they can radiate like a lot of tiny

dipole antenna In radio and telecommunications a dipole antenna or doublet is one of the two simplest and most widely used antenna types, types of antenna; the other is the monopole antenna, monopole. The dipole is any one of a class of antennas producin ...

s. This cloud is very bright at infra-red wavelengths due to thermal emission from the large dust grains, but very little emission would be expected at microwave wavelengths by this type of dust. Instead there is a broad bump of signal centered on 22 GHz, a factor of 50 above the expected level of signal.

References

Cosmic microwave background experiments {{physical-cosmology-stub