Spitzer’s legacy
ON JANUARY 30, 2020, an era in astronomy will end. On this date, NASA’s Spitzer Space Telescope will send us its final observations, finishing a remarkable, 16-year exploration of the universe at infrared wavelengths.
Spitzer is one of the four Great Observatories, a quartet of space telescopes launched by NASA in the 1990s and early 2000s to unveil the multiwavelength universe, from infrared to gamma ray. Originally known as the Shuttle Infrared Telescope Facility (SIRTF), the telescope concept came to life in 1971, when NASA was seeking payloads to fly on the Space Shuttle. Converted in 1984 to a free-flying observatory orbiting Earth, SIRTF underwent a series of (sometimes drastic) redefinitions before being launched as a Great Observatory into a heliocentric (i.e. Sun-centred) orbit in August 2003.
Although the public often latches onto Hubble (another Great Observatory) as the pinnacle of scientific discovery machines, astronomers already knew while planning Spitzer that there was at least as much to explore at infrared wavelengths as at visible ones. Infrared radiation pierces our galaxy’s giant molecular clouds to reveal the dusty cocoons of forming stars. It also unveils distant galaxies heavily enshrouded in cosmic dust. Furthermore, because the universe’s expansion stretches the light from distant galaxies to longer wavelengths, it is infrared, not visible light, that enables us to look back in time to the universe’s first few billion years.
Still, back when mission planners were first envisioning what Spitzer would do, no planets were known to orbit stars other than the Sun, and the most distant objects known lay 10 to 11 billion years in the universe’s past. Now, Spitzer has not only seen exoplanets crossing in
