Back In this computer-generated image, individual sources of EUV radiation have been plotted in this all-sky projection. The EUVE telescopes detected a total of 739 sources. Most of these sources (268 of them) are cool stars of spectral type F,G,K, and M, with active coronae that emit in the EUV. EUVE detected 104 white dwarf stars, 24 hot stars with early spectral types, 16 cataclysmic variables, 36 active nuclei of galaxies beyond our own Milky Way, and a few each of other astronomical objects that include planetary nebulae, neutron stars, novae, supernova remnants and solar system objects. EUVE sources have been identified as belonging to the various categories through several methods that include (a) matching source locations with previously observed and identified sources that emit radiation in several wavelengths (EUV, visible, X-ray, etc.) and (b) obtaining spectra of EUV sources from the ground using visible light telescopes. The EUVE Optical (or Visible) Identification program is currently undertaking an ambitious campaign to acquire spectra of EUVE sources that are still unidentified (251 of them). The identification procedure involves comparing the optical (visible) radiation spectra of these unidentified EUVE sources with template or standard spectra that are typical of a white dwarf, late or early type star, cataclysmic variable, etc. The 251 currently unidentified sources are a very important group because they are extremely dominant in the EUV spectral region but must be relatively inconspicuous at other wavelengths. Whether they share a similar morphological distribution to the sources indentified using existing catalogs that probe other wavelengths, or whether they might contain hitherto unknown classes of objects, can only be answered through a systematic optical (visible) identification campaign. Next
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