Spitzer’s Cold Look at Space

To get a clear view of infrared emissions from celestial objects, the Spitzer Space Telescope has been cryogenically cooled—and what sights it has seen.

Michael Werner in American Scientist:

ScreenHunter_05 Nov. 20 10.06 In astrophysical observations, more is more—imaging across multiple wavelengths leads to richer information. One electromagnetic band in which most celestial bodies radiate is the infrared: Objects ranging in location from the chilly fringes of our Solar System to the dust-enshrouded nuclei of distant galaxies radiate entirely or predominantly in this band. Thus, astrophysicists require good visualization of these wavelengths. The problem, however, is that Earth is a very hostile environment for infrared exploration of space, as the atmosphere also emits in the infrared spectrum and additionally absorbs much of the incoming signal. Even heat produced by a telescope itself can degrade its own clarity.

Starting at the end of the 1950s, a number of pioneering groups confronted this challenge and carried out increasingly exciting infrared investigations from ground-based, airborne and balloon-borne observatories. This work continues in parallel with space-based exploration; infrared capabilities form an integral component of current and planned ground-based telescopes with apertures of 10 to 30 meters in diameter.

But the best solution is to send into space a telescope that’s cooled by liquid helium to temperatures just a few degrees above absolute zero. NASA’s Space Infrared Telescope Facility (SIRTF) was proposed in the early 1970s and finally launched in August 2003. It was renamed the Spitzer Space Telescope in honor of the late Lyman Spitzer, Jr., an astrophysicist who was one of the first to propose the idea of placing a large telescope in space, and was also the driving force behind the Hubble Space Telescope.

More here.