Spitzer’s debris disk legacy from main-sequence stars to white dwarfs

The Spitzer Space Telescope enabled the detection and characterization of infrared excess — attributed to thermal emission from circumstellar dust — towards more than 1,000 main-sequence stars and more than 40 white dwarfs. These systems have been dubbed ‘debris disks’ because they are believed to be planetary systems in which the observed dust is generated by collisions among otherwise undetected planetesimals, planetary embryos and planets. With its superb sensitivity and good spatial resolution, Spitzer revolutionized the study of debris disks, increasing the number of known systems by an order of magnitude and providing detailed disk demographics and properties for a substantial sample for the first time. In doing so, Spitzer set the stage for detailed characterization of the dust using Herschel, the Atacama Large Millimeter/submillimeter Array and high-contrast imaging instruments such as the Hubble Space Telescope’s NICMOS and STIS, the Very Large Telescope’s SPHERE, and the Gemini Planet Imager. Spitzer played a vital role in demonstrating that planetary systems are present and active around white dwarfs. Specifically, it showed that the origin of pollution in white dwarfs is circumstellar material. Finally, Spitzer’s longevity enabled time-domain studies of young debris disks that are actively forming terrestrial planets and rejuvenized the study of dusty white dwarfs. Spitzer’s legacy will endure into the next decade with discoveries expected from new instruments on SOFIA, the James Webb Space Telescope and SPHEREx.