The NASA Spitzer Space Telescope.

The National Aeronautics and Space Administration's Spitzer Space Telescope (formerly the Space Infrared Telescope Facility) is the fourth and final facility in the Great Observatories Program, joining Hubble Space Telescope (1990), the Compton Gamma-Ray Observatory (1991-2000), and the Chandra X-Ray Observatory (1999). Spitzer, with a sensitivity that is almost three orders of magnitude greater than that of any previous ground-based and space-based infrared observatory, is expected to revolutionize our understanding of the creation of the universe, the formation and evolution of primitive galaxies, the origin of stars and planets, and the chemical evolution of the universe. This review presents a brief overview of the scientific objectives and history of infrared astronomy.

Recent Changes in the Near-Infrared Structure of eta Carinae.

Near-infrared imaging at two phases in the 5 yr spectroscopic cycle of eta Carinae reveals changes in the spatial structure of the inner core that may be related to recently reported near-infrared photometric variability. The central source changed from a pointlike object to a more extended, bipolar or shell structure. This behavior is reminiscent of changes observed in the radio continuum.

Confirmation of dust condensation in the ejecta of supernova 1987a.

Shortly after its outburst, we suggested that supernova 1987a might condense a dust shell of substantial visual optical thickness as many classical novae do and predicted that dust might form within a year after the explosion. A critical examination of recent optical and infrared observations reported by others confirms that dust grains had begun to grow at a temperature of 1000 K after 300 days and that the dust shell had become optically thick by day 600. After day 600, the infrared luminosity closely followed the intrinsic luminosity expected for thermalized 56Co gamma rays, demonstrating that the luminosity is powered by radioactivity and that the dust is outside the radioactivity zone.

The infrared spectrum of comet Bradfield (1987s) and the silicate emission feature.

Infrared (1-20 micrometers) observations of comet Bradfield (1987s) from three observatories are reported. Silicate emission is prominent in all the data, from heliocentric distance r=0.87 to 1.

On the possibility of dust condensation in the ejecta of supernova 1987a.

We suggest that supernova 1987a may condense dust of substantial visual optical thickness as do many novae. The dust will act as a calorimeter of the photon luminosity of any central engine that is dominant at the time of dust formation. Observations of novae suggest that dust formation may occur when the expanding ejecta reach a temperature of 1000 K.

The formation of stellar systems from interstellar molecular clouds.

Star formation, a crucial link in the chain of events that led from the early expansion of the universe to the formation of the solar system, continues to play a major role in the evolution of many galaxies. Observational and theoretical studies of regions of ongoing star formation provide insight into the physical conditions and events that must have attended the formation of the solar system. Such investigations also elucidate the role played by star formation in the evolutionary cycle which appears to dominate the chemical processing of interstellar material by successive generations of stars in spiral galaxies like our own.

Optical polarization and infrared spectrum of a possible protostar in a reflection nebula.

The star HD 200775 illuminates the reflection nebula NGC 7023. This star is one of a small group of Ae and Be stars associated with nebulosity and proposed by Herbig as candidates for newly formed stars of moderately large mass. The system is a part of a large dust complex more than a degree in extent.

Interstellar silicate absorption bands.

Interstellar silicate absorption is observed in the direction of the galactic centre. Most interstellar silicon seems to be in silicate form.