In 2003, NASA launched a 34-inch infrared telescope called Spitzer. For 17 years, it looked through cosmic dust and revealed a hidden universe

NASA’s Spitzer Space Telescope ended its mission in 2020 after more than 16 years in space, but its infrared observations transformed our view of the universe. Unlike telescopes that primarily observe visible light, Spitzer could peer through thick clouds of cosmic dust that often obscure stars, planets and other celestial objects.

The Spitzer Space Telescope, formerly known as the Space Infrared Telescope Facility (SIRTF), was the fourth and final of NASA’s “Great Observatories,” following the Hubble Space Telescope, launched in 1990; the Compton Gamma Ray Observatory, launched in 1991; and the Chandra X-ray Observatory, launched in 1999.

Spitzer carried an 85-centimeter (34-inch) infrared telescope along with three scientific instruments housed within its cryogenic telescope assembly. It was launched in August 2003 and spent more than 16 years studying the universe in infrared wavelengths.


One of the mission’s early breakthroughs came in 2005, when Spitzer captured direct light from extrasolar planets for the first time. More discoveries followed, including observations of light from some of the earliest objects in the universe, the first mapping of weather on an extrasolar planet, the detection of water vapor on another exoplanet and the identification of a previously unknown ring around Saturn, known as the Phoebe ring.

In August 2010, Spitzer data helped astronomers identify the first known carbon-rich planet, WASP-12b, orbiting another star. In October 2012, observations from the telescope also contributed to a more precise measurement of the Hubble constant, the rate at which the universe is expanding.

Then, in February 2017, NASA announced one of Spitzer’s most famous discoveries: the first known system of seven Earth-sized planets orbiting a single star. Known as the TRAPPIST-1 system, it included three planets firmly located within the star’s habitable zone—the region where conditions could potentially allow liquid water to exist on a rocky planet.

The discovery set a record for the largest number of potentially habitable-zone planets found around a single star outside our solar system at the time.

Spitzer’s infrared vision was particularly valuable for studying objects hidden behind cosmic dust. During its mission, it observed newborn stars buried inside dusty clouds, distant galaxies billions of light-years away and structures near the center of the Milky Way that are difficult to see in visible light.

By detecting infrared radiation, Spitzer could effectively look through some of the thickest curtains of dust in space. Its observations helped astronomers investigate how stars and planets form, study the structure of our galaxy and better understand distant planetary systems.

After more than 16 years of exploration, Spitzer was decommissioned on Jan. 30, 2020. But its scientific legacy did not end when the telescope was switched off. Data collected throughout the mission continues to be studied and used in new research.

Spitzer may be retired, but the universe it revealed is still being explored—one infrared discovery at a time.