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Cosmic infrared background (CIB) is a mysterious infrared light coming from outer space. It is slowly being resolved into specific sources by infrared telescopes. In some ways it is analogous to the cosmic microwave background, but at shorter wavelengths. ==History== Recognizing the cosmological importance of the darkness of the night sky (Olbers' paradox) and the first speculations on an extragalactic background light dates back to the first half of the 19th century. Despite its importance, the first attempts were made only in the 1950-60s to derive the value of the visual background due to galaxies, at that time based on the integrated starlight of these stellar systems. In the 1960s the absorption of starlight by dust was already taken into account, but without considering the re-emission of this absorbed energy in the infrared. At that time Jim Peebles pointed out, that in a Big Bang-created Universe there must have been a cosmic infrared background (CIB) - different from the cosmic microwave background - that can account for the formation and evolution of stars and galaxies. In order to produce today's metallicity, early galaxies must have been significantly more powerful than they are today. In the early CIB models the absorption of starlight was neglected, therefore in these models the CIB peaked between 1-10μm wavelengths. These early models have already shown correctly that the CIB was most probably fainter than its foregrounds, and so it was very difficult to observe. Later the discovery and observations of high luminosity infrared galaxies in the vicinity of the Milky Way showed, that the peak of the CIB is most likely at longer wavelengths (around 50μm), and its full power could be ~1-10% of that of the CMB. As Martin Harwit emphasized, the CIB is very important in the understanding of some special astronomical objects, like quasars or ultraluminous infrared galaxies, which are very bright in the infrared. He also pointed out, that the CIB cause a significant attenuation for very high energy electrons, protons and gamma-rays of the cosmic radiation through inverse Compton scattering, photopion and electron-positron pair production. In the early 1980s there were only upper limits available for the CIB. The real observations of the CIB began after the era of astronomical satellites working in the infrared, started by the Infrared Astronomy Satellite (IRAS), and followed by the Cosmic Background Explorer (COBE), the Infrared Space Observatory (ISO) and the by the Spitzer Space Telescope. Exploration of the CIB was continued by the Herschel Space Observatory, launched in 2009. The Spitzer wide area surveys have detected lumpiness in the CIB.〔Taylor, Kate. ("NASA spots glow of universe's first objects." ) ''TG Daily'', June 8, 2012.〕 A summary on the history of CIB research can be found in the review papers by M.G. Hauser and E. Dwek (2001)〔 〕 and A. Kashlinsky (2005).〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cosmic infrared background」の詳細全文を読む スポンサード リンク
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