Spitzer Space Telescope
Stars and galaxies emit much of their energy in the infrared region of the spectrum. The Spitzer Space Telescope is the latest of NASA’s Great Observatories, designed to observe this infrared radiation and use it to map the sites of star formation in both our Galaxy and external galaxies.
Spitzer was launched on 25 August 2003 from Kennedy Space Center in Florida, USA. The Delta rocket put the observatory into orbit around the Sun and it is currently about 15 million kilometres away from the Earth. This orbit allows the telescope to be kept very cold, at a temperature of around -268 celcius. Warm objects, such as the Earth and the Sun, produce large amounts of infrared radiation which would swamp the faint signals from distant galaxies, so the telescope is kept far away from the planet and is protected from the Sun by a heat shield.
The telescope is relatively small compared to ground-based telescopes, with a primary mirror of only 85cm in diameter. There are three science instruments onboard the observatory: two cameras (IRAC and MIPS) which take photographs in a wide range of infrared ‘colours’, and a spectrograph (IRS) which separates the infrared light into a spectrum for more detailed analysis. These instruments are designed to study the radiation emitted by stars and interstellar dust, in particular around sites of newly-forming stars.