![]() ![]() Placed in an orbit parallel to that of our planet, at a distance of some 1.5 million kilometres (four times the distance from the Earth to the Moon), the JWST will avoid these drawbacks. And it shouldn't be forgotten that the observation equipment itself emits infrared radiation. The little remaining infrared radiation that does get through suffers from interference by a host of more powerful sources, both natural and artificial.Īlthough telescopes have been installed in high-altitude observatories, balloons and aircraft to try to mitigate these problems, satisfactory detection of faint energy sources in the sky has proved impossible. ![]() In fact, it is this absorption that is responsible for the greenhouse effect caused by gases such as carbon dioxide and water vapour. As for ground-based observations, infrared radiation from space is unfortunately massively absorbed by the atmosphere, and at wavelengths between 10 and 800 micrometres is even completely absent. For instance, hydrogen, the main component of the interstellar medium, is almost invisible outside these infrared band emissions, unless it is heated to very high temperatures. Although these are not cold, their energy emissions exhibit an apparent shift towards the infrared due to the expansion of the Universe."Ĭertain molecules are also easier to detect at these frequencies. This will enable us to see relatively cold objects, such as the dust and interstellar gas in galaxies (including our own), as well as planets and very distant galaxies. "This new instrument will make it possible to observe at wavelengths ranging from around 0.5 to 30 micrometres, providing hugely increased sensitivity. "The JWST fills a gap between Hubble, which only ventures into the near infrared, and the European Space Agency (ESA)'s space telescopes Herschel and ISO 1 which go deep into the far infrared," says Daniel Rouan, research professor emeritus at the LESIA 2. ![]()
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