Astrophysical plasmas at temperatures in the range (0.5-5)x10SK that occur e.g. in interstellar space, in the extended atmospheres around stars of essentially all spectral types, including the numerous late-type stars with low photospheric temperatures, and in the atmospheres of highly evolved stars, can best be studied at extreme ultraviolet wavelengths where they release the bulk of their energy. We report here the current development status of a Im-normal-incidence-EUV-telescope that will be flown on an ARIES rocket to observe the spectra of nearby stars in the 350 -700 mm range.Observations at optical, UV and x-ray wavelengths have demonstrated the existence of astrophysical plasmas at temperatures of (0.5-5)x105K. Interstellar matter at a temperature of roughly 50 000 K has been discovered in many regions by the IUE-sateilite, an even hotter phase at a temperature of roughly 50 000 K had already been discovered before by the COPERNICUS satellite. ~he IUE satellite has also led to the discovery of extended hot envelopes around many late-type stars with low photospheric temperatures and thus greatly extended earlier work in this direction based on COPERNICUS observations. Most recently, the EINSTEIN observatory has detected x-rays from stars of essentially all spectral types indicating the widespread occurence of hot outer layers. Also, old stars on their way towards or in their final evolutiory state are expected to have surface temperatures of the order of I05K but only very few of these have actually been studied in detail to date.There is no question that it would also be highly desirable to observe extragalactic objects at EUV wavelengths, in particular active galaxies and quasars, but it is very doubtful whether it will ever be possible to penetrate the foreground Space Science Reviews 30 (1981) 575-580.
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