NASA's Spitzer Space Telescope is retiring after 16 years. Its incredible infrared images revealed nebulae and galaxies as we'd never seen before.

· One of NASA's most powerful space telescopes, the Spitzer Space Telescope, retires today after 16 years.
· Spitzer measured infrared light, which allowed it to see through clouds of gas and dust in space.
· The telescope generated some of the most awe-inspiring images that we have of nebulae and galaxies, and led to many...