Universe

Hubble Deep Field - North NASA/HST/R. Williams

Extragalactic Surveys

The unprecedented sensitivity and efficiency of Spitzer makes the observatory an ideal tool for conducting surveys of the extragalactic (external to our Milky Way) infrared sky. Early in its mission, Spitzer will conduct a variety of mid- and far-infrared imaging surveys. Deep and small-area surveys, including one centered on the northern Hubble Deep Field, will probe the early and distant Universe at redshifts approaching 5, corresponding to a distance of about 12 billion light years. Shallower surveys will also be conducted over larger areas, vastly increasing the number of cataloged infrared galaxies. One survey will cover about 70 square degrees, or 350 times the area of the full Moon, out to redshifts of 2.5 (about 10 billion light years). This survey will reveal more than two million galaxies, or nearly 30,000 galaxies per square degree. As with any extragalactic survey, the utility of the Spitzer data will be greatly enhanced by companion observing programs at other wavelengths and with other space-borne and ground-based telescopes.

Evolution of Galaxies Montage Courtesy of NASA/IPAC/C. Lonsdale

Origin and Evolution of Galaxies

At a cosmological redshift of 5, the visible light emitted by young galaxies is redshifted to near-infrared wavelengths, placing them within Spitzer's observational regime. Astronomers will exploit this capability to observe dusty protogalaxies being born in the young and distant Universe. By examining galaxy properties at different redshifts, or cosmological ages, scientists will trace the history of star formation as a function of environment, and try to explain why the global star formation rate was much higher seven billion years ago. These data will also enable studies of the spatial distribution and clustering of galaxies. Moreover, Spitzer data (when combined with x-ray data) will permit astronomers to ascertain the extent to which starburst galaxies and dusty active galactic nuclei contribute to the global infrared luminosity.

All-Sky Maps of the Infrared Background NASA/COBE/M. Hauser

Cosmic Infrared Background

The cosmic infrared background (CIRB) is a very faint infrared glow in the distant Universe, presumably produced by the juxtaposition of countless unseen galaxies that are too faint to be detected individually. By studying the intensity of the CIRB at different wavelengths, astronomers can interpret the history of star formation, the history of galaxy formation, and the presence or absence of dust in the earliest primeval galaxies. Spitzer should not only confirm the recent detections of this background light, but will characterize the sources(s) of this radiation.

Submillimeter Image of Hubble Deep Field - North JAC/JCMT/D.H. Hughes

Optically Unidentified IR Sources

It is a well-known observation that some celestial sources emit more (if not most) of their radiation at particular wavelengths. It is certain that Spitzer will discover unusual infrared sources with no known optical counterpart. Spectroscopic measurements with Spitzer will allow astronomers to obtain the redshift, and hence the inferred distance, of these mysterious objects. The Spitzer data will be combined with observations at other wavelengths, such as x-ray and radio, to aid in the interpretation of the unidentified infrared sources.

Serendipity

Spitzer's powerful combination of great sensitivity, high observing efficiency, large-format detector arrays, and a long cryogenic lifetime represents a giant leap beyond current capabilities. This potent combination will produce a rich legacy of scientific results that will be studied for decades. As history has repeatedly shown, astronomers can also expect the unexpected: serendipitous discoveries of unanticipated phenomena.

The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory. This website is maintained by the Spitzer Science Center, located on the campus of the California Institute of Technology and part of NASA's Infrared Processing and Analysis Center. Privacy Policy