IUE dominated ultraviolet space astronomy for nearly two decades. It analysed ultraviolet light, in a wavelength range from 1150 to 3200 Ångström units, which is blotted out by the Earth's atmosphere. Operating far above the atmosphere, IUE generated spectra showing intensities at different wavelengths, coming from the selected objects in the sky. To an astrophysicist, such spectra are much more informative than images, revealing much about the mechanisms that produce and dissipate the objects' energy. Temperatures, motions, magnetism and chemical composition are all discernible in the ultraviolet spectra.

Stars

As a result, astronomers have a far better picture of the hot atmospheres of stars than they did before IUE's launch. Even the Sun, a quiet star of moderate size, possesses a very hot atmosphere emitting ultraviolet light, which is now being monitored non-stop by the ESA-NASA solar spacecraft SOHO. Some other stars, ranging from small white dwarfs to large, massive stars, give off ultraviolet emissions from their very hot surfaces. Hot and fierce winds of gas emitted from stars have a profound effect on the lives and environments of the stars, and on any companions caught up in the winds. IUE unmasked the ultraviolet behaviour of a large menagerie of different star types, which heralds profound revisions in astrophysical ideas resulting from the observations.

Galaxies

IUE's has contributed new knowledge about galaxies. These vast assemblies of stars also reveal violent behaviour in ultraviolet light. In a special campaign, a multinational team used IUE to observe the stormy galaxy NGC 5548 some 60 times in eight months.

As a result, they discovered effects of central outbursts spreading from hot regions at the very core of the galaxy to adjacent cooler regions, in a timescale of weeks. In galaxy NGC 7469, observed simultaneously by IUE and by the X-ray satellite Rossi XTE, the timescale shrank to days.

Quasars

Quasars are erupting galaxies observable at great distances, and their examination by ultraviolet light, by IUE and more recently by the Hubble Space Telescope, give special clues to the nature of the gas in the almost empty spaces between galaxies, and to the manufacture of the chemical elements within the galaxies. Quasar studies occupy an important place in the effort to understand the character and evolution of the Universe at large. Ultraviolet data on element-making suggest that massive stars, far bigger than the Sun, were more numerous when the galaxies were young.

	Supernova
	Long Lifetime