NASA calls Lyman Spitzer Jr. (1914-1997) one of the 20th century's greatest scientists. The longtime Princeton astrophysicist lobbied for a large space telescope as early as 1946, work that culminated in the launch of the Hubble Space Telescope in 1990. After Spitzer's death in 1997, NASA continued to develop the Great Observatories Program, a group of four space-based telescopes each observing the universe in a different kind of light. Besides Hubble, the other telescopes include Compton Gamma Ray Observatory (CGRO) and the Chandra X-Ray Observatory (CXO). The final telescope was launched in 2003, consisting of "a large telescope and three cryogenically cooled instruments capable of studying the universe at near-to-far infrared wavelengths." NASA named this new space-flyer the Spitzer Space Telescope in honor of the visionary scientist. As this revolutionary telescope now approaches retirement — scheduled for Jan. 30, 2020 — here's a look at some of the incredible views it has given us over the years, including this image of the Cat's Paw Nebula, a star-forming region inside the Milky Way.
Editor's note: This story has been updated with new information since it was originally published in November 2011.