In pictures: Spitzer - Infrared telescope
Cool mission

Most infrared radiation from celestial objects is absorbed by the Earth's atmosphere, so an infrared telescope is best used from space.

As Spitzer's own components will emit some infrared, its instruments have to be super-cooled to near absolute zero, using a tank of liquid helium.

Spitzer also sits millions of km away from Earth's infrared "glow".

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