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Infrared astronomy from space

IRAS (InfraRed Astronomy Satellite) was the first orbiting celestial infrared observatory in which most of the serious technological problems that opposed a systematic investigation from space were solved. Similar to a giant cryostat orbiting at an altitude of 900 km, IRAS – with its 60 cm objective – in the late eighties produced a map containing 300,000 sources of different types, including galaxies thousands of times brighter than the Milky Way, but radiating exclusively in the infrared. It revealed the presence of protoplanetary disks around numerous stars (β Pictoris, Vega) and that of cirriform formations scattered throughout the galactic space.

Subsequently, it was the turn of COBE (Cosmic Background Explorer), a cosmological probe, to investigate in the infrared the fossil radiation in order to capture the thermal inhomogeneities related to the primitive genetic centers of the Universe (protogalaxies and early generations of stars). In the investigation, the probe has also provided a general view of the dust that thickens in the disk and in the bulb of our Galaxy, thus improving the knowledge of its evolutionary mechanisms.

Equally and perhaps more important than IRAS was the orbiting infrared observatory of the European Space Agency (ESA), namely ISO, (Infrared Space Observatory) with 60 cm optics, which worked in space from 17 November 1996 to 8 April 1998. In 2003, NASA has completed the complex of the 4 large space observatories of its scientific program with the infrared observatory SIRTF (Space InfraRed Telescope Facility, renamed Spitzer Space Telescope after the launch), equipped with a 90 cm mirror and a spectrograph, refrigerated with liquid helium.

On the European side, always in the field of infrared space astronomy, the European Space Agency has defined the projects for the analogue of the Spitzer Space Telescope, that is for FIRST (already renamed Herschel), which will operate in the far infrared and will be put into orbit in 2007. Thanks to their extraordinary qualities of sensitivity and spatial resolution, with these infrared space observatories astronomers promise to observe celestial infrared sources a thousand times fainter than those known so far, and to discover the invisible component – dead stars, brown dwarfs, cometary reservoirs, extra-solar planetary bodies, intergalactic halos, etc. – that could be a not negligible part of the universe. – that could constitute a non-negligible part of the so-called dark matter.