2019

James Webb Space Telescope

James E. Webb (1906–1992)

The power and beauty of space-based astronomy has been dramatically demonstrated by a variety of small, medium, and large space telescopes, culminating in the successful missions of NASA’s four Great Observatories: the Hubble Space Telescope (HST), Compton Gamma-Ray Observatory, the Spitzer Space Telescope, and the Chandra X-ray Observatory. Like all complex spacecraft, however, these missions have finite lifetimes. Only HST has been capable of being repaired or upgraded by astronauts—but the retirement of the space shuttle in 2011 means the end of service calls to HST. NASA has thus been pondering its replacement for some time.

NASA’s planned next-generation space telescope is known as the James Webb Space Telescope (JWST), after NASA’s second administrator, James E. Webb, who oversaw the space agency during the Mercury, Gemini, and early Apollo astronaut programs. Planning for JWST actually began in 1989, the year before HST was launched. Over the course of more than 20 years the design has been revised numerous times. Currently the telescope is in final development, with a scheduled launch in 2019.

JWST will combine some capabilities from the Hubble Space Telescope (such as high-resolution imaging), the Keck Observatory (a precisely controlled segmented mirror design), and the Spitzer Space Telescope (sensitivity in the infrared) to become the scientific workhorse for space-based astronomy for at least a decade. Its 21-foot (6.5-meter) segmented primary mirror has six times the light-collecting area of HST, and the telescope is cooled to only 40 degrees above absolute zero to make it highly sensitive to faint, distant objects in the cosmos.

Astronomers have ambitious plans for JWST science across the entire range of visible through infrared astronomy and astrophysics research areas. Major science themes include studying the first stars and galaxies, formed after the early dark ages of the universe; studies of dark matter; new stars and their associated protoplanetary disks of gas and dust; the formation of planets; and the search for extrasolar planets and other cosmic environments conducive to life. JWST should be a spectacular astronomical discovery machine!

Artist’s conception of the James Webb Space Telescope, with its gold-coated primary mirror (21 feet [6.5 meters] in diameter) and deployed radiation shields, designed to protect the telescope from the contaminating light and heat of the Sun, Earth, and Moon.