Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. The launch date will be at or after 2015. The current design envisions three free-flying space telescopes, each at least 3 meters in diameter, flying in formation as an astronomical interferometer. These telescopes will redirect the light to the main spacecraft which will contain the beam combiner, spectrographs and cameras for the interferometer array, and which will also act as a communications hub. The European Space Agency (ESA), established in 1975, is an inter-governmental organisation dedicated to the exploration of space, currently with 17 member states. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ... The existence of extraterrestrial life remains hypothetical though human beings continue to search Extraterrestrial life is life that may exist and originate outside the planet Earth. ... A space observatory is any object in outer space which is used for observation of distant planets, galaxies, and other outer space objects. ... Diagram showing a possible layout for an astronomical interferometer, with the mirrors laid out in a parabolic arrangement (similar to the shape of a conventional telescope mirror). ...

The space telescope will observe in the infrared part of the electromagnetic spectrum. As well as studying extrasolar planets, the instrument will probably have a general purpose imaging mode which will produce very high resolution (i.e. milliarcsecond) infrared images, allowing detailed study of a variety of astrophysical processes. The infrared spectrum was chosen because an Earth-like planet is only outshone by its star by a factor of a million there; in the visible spectrum an Earth-like planet is outshined by its star by a factor of a billion. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency HF = High frequency... Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ...

The planet search would use a nulling interferometer configuration. In this system, phase shifts would be introduced into the three beams, so that light from the central star would suffer destructive interference and cancel itself out. However, light from any orbiting planets would not cancel out, as the planets are offset slightly from the position of the star. This would allow planets to be detected, despite the much brighter signal from the star. Nulling interference pattern, Courtesy NASA/JPL-Caltech Nulling interferometry is a type of interferometry in which two or more signals are mixed to produce observational regions in which the incoming signals cancel themselves out. ...

For planet detection, the instrument would operate in an imaging mode. To detect an Earth-like planet would require about 10 hours of observation in total, spread out over several months. Once a planet is detected, a more detailed study of its atmosphere would be made by taking an infrared spectrum of the planet. By analysing this spectrum, the chemistry of the atmosphere could be determined, and this could provide evidence for life on the planet. The presence of oxygen in the atmosphere would be evidence for life, as oxygen is too reactive to exist without being continually replenished as a byproduct of biological photosynthesis. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... The leaf is the primary site of photosynthesis in plants. ...

The interferometric version of NASA's Terrestrial Planet Finder mission is very similar in concept to Darwin, and also has very similar scientific aims. Given this, and the technical difficulties inherent in such a project, it seems unlikely that both instruments will be built; a collaborative project is more likely. According to NASA's 2007 budget documentation, however, "The Terrestrial Planet Finding project has been deferred indefinitely." This article or section does not cite its references or sources. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a mothballed NASA telescope system that would be capable of detecting extrasolar terrestrial planets. ...

Antoine Labeyrie has proposed a much larger space-based astronomical interferometer similar to Darwin, but with the individual telescopes positioned in a spherical arrangement and with an emphasis on interferometric imaging. The spherical geometry reduces the amount of pathlength compensation required in re-pointing the interferometer array. This "Hypertelescope" project would be much more expensive and complex than the Darwin and TPF missions, involving many large free-flying spacecraft. French astronomer, graduated from the grande école SupOptique (École supérieure doptique), he is the inventor of the interferometric astronomy. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ...

See also

• Extrasolar planet

Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ...

External links

• DARWIN The official ESA homepage
• The principles of nulling interferometry
• Darwin (Space IR Interferometry Project) on the Internet
• The DARWIN Nulling Interferometer Breadboard II
• The Achromatic Phase Shifter
• The DARWIN Breadboard Cryogenic Optical Delay Line