Astronomers have embarked upon a new era brimming with never-before-seen celestial objects and new views of classic astronomical marvels. That was the message sent to the public on December 18th as NASA released the first scientific images from the Space Infrared Telescope Facility (SIRTF), now called the Spitzer Space Telescope. As one principal investigator remarked, "We can expect a flood of discoveries over the next five years."
Unlike the Hubble Space Telescope, which is tuned to see the cosmos in visible light (with some spillover into the near-infrared and near-ultraviolet), Spitzer is an infrared-only telescope. This affords it the opportunity to see things never seen before in astronomy. Most notably, dust clouds are often opaque to visible or near-infrared light. But Spitzer, looking in lower-energy wavelengths, can see through the dusty cloak, unveiling the mysteries that lie beneath. These treasures include newly forming planets and the shrouded birthing rooms of stars and galaxies.
Spitzer will detect and discern the feeble heat coming from objects vast distances away. To do so the entire instrument is cryogenically cooled with liquid helium to 5.5° Kelvin (–268°C). Unfortunately, the spacecraft carries only a fixed amount of coolant on board, thus limiting its expected lifetime to just 5.8 years — double the expected lifespan at launch. Moreover, Spitzer cannot be serviced. It resides in an Earth-trailing orbit, slowly drifting from our planet with each passing day. As such, space shuttles can't reach it.
The last of NASA's four Great Observatories (its sister scopes are the Hubble Space Telescope, Compton Gamma-Ray Observatory, and Chandra X-ray Observatory), the Spitzer Space Telescope hosts a trio of powerful instruments: the Infrared Array Camera (IRAC) will observe simultaneously in four wavelengths centered at 3.6, 4.5, 5.8, and 8.0 microns; the Multiband Imaging Photometer for Spitzer (MIPS) can do both photometric mapping and high-resolution imaging at 24, 70, and 160 microns; and an Infrared Spectrograph (IRS) that will take spectral images from 5.3 to 40 microns.
Since its launch, the spacecraft has been exceeding expectations, both operationally and scientifically. Some initial results from images received primarily during the science verification phase include:
SIRTF was renamed yesterday in honor of the late Lyman Spitzer, Jr. In 1946 Spitzer suggested placing a large telescope in space as a way to eliminate disturbances caused by Earth's atmosphere. Project officials said the announcement of the new name was withheld until it was certain the observatory was operating properly.
With Spitzer, infrared astronomy has "crossed a new threshold," says project scientist Michael W. Werner (Jet Propulsion Laboratory).