'The little telescope that could' has retired. It changed how we see the universe

By Ashley Strickland, CNN

Updated 4:31 PM ET, Fri January 31, 2020

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For 16 years, the Spitzer Space Telescope acted as our infrared detective, observing things otherwise invisible -- including exoplanets and distant galaxies. Here are some of the best images and illustrations created using Spitzer data.
Photos: The best of the Spitzer Space Telescope
For 16 years, the Spitzer Space Telescope acted as our infrared detective, observing things otherwise invisible -- including exoplanets and distant galaxies. Here are some of the best images and illustrations created using Spitzer data.
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The discovery of the TRAPPIST-1 system revealed seven Earth-size, rocky planets orbiting a single star. Robert Hurt and Tim Pyle presented this illustration when the discovery was announced to showcase the habitable zone of the star -- too close and the planets are too hot for liquid water to remain on the surface, while more distance from the star means water would freeze.
Photos: The best of the Spitzer Space Telescope
The discovery of the TRAPPIST-1 system revealed seven Earth-size, rocky planets orbiting a single star. Robert Hurt and Tim Pyle presented this illustration when the discovery was announced to showcase the habitable zone of the star -- too close and the planets are too hot for liquid water to remain on the surface, while more distance from the star means water would freeze.
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This illustration of the TRAPPIST planets reveals more about how their surfaces might appear.
Photos: The best of the Spitzer Space Telescope
This illustration of the TRAPPIST planets reveals more about how their surfaces might appear.
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This illustration shows what it might be like to stand on the surface of TRAPPIST-1f, with liquid water on the surface and other planets visible in the sky.
Photos: The best of the Spitzer Space Telescope
This illustration shows what it might be like to stand on the surface of TRAPPIST-1f, with liquid water on the surface and other planets visible in the sky.
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This infrared image from Spitzer shows a cloud of gas and dust full of bubbles, which are inflated by wind and radiation from massive young stars. Each bubble is filled with hundreds to thousands of stars, which form from dense clouds of gas and dust.
Photos: The best of the Spitzer Space Telescope
This infrared image from Spitzer shows a cloud of gas and dust full of bubbles, which are inflated by wind and radiation from massive young stars. Each bubble is filled with hundreds to thousands of stars, which form from dense clouds of gas and dust.
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The dreamy spiral galaxy M81 is presented in crisp detail thanks to a collaboration between Spitzer, Hubble and NASA's Galaxy Evolution Explorer.
Photos: The best of the Spitzer Space Telescope
The dreamy spiral galaxy M81 is presented in crisp detail thanks to a collaboration between Spitzer, Hubble and NASA's Galaxy Evolution Explorer.
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Spitzer captured hundreds of thousands of stars as they swirl at the center of the Milky Way galaxy.
Photos: The best of the Spitzer Space Telescope
Spitzer captured hundreds of thousands of stars as they swirl at the center of the Milky Way galaxy.
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This illustration shows what HD 219134b might look like, the nearest confirmed rocky exoplanet found outside of our solar system.
Photos: The best of the Spitzer Space Telescope
This illustration shows what HD 219134b might look like, the nearest confirmed rocky exoplanet found outside of our solar system.
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This image shows an artist's impression of 10 hot Jupiter exoplanets. Clockwise from top left to lower left, these planets are WASP-12b, WASP-6b, WASP-31b, WASP-39b, HD 189733b, HAT-P-12b, WASP-17b, WASP-19b, HAT-P-1b and HD 209458b. Hot Jupiters were some of the first exoplanets to be discovered. Although they're in orbits too close to their stars to support life on the planet's surface, these intriguing gas giants are unlike any planet in our solar system.