DETECTION OF LUMINOUS INTRACLUSTER EXTREME-ULTRAVIOLET EMISSION FROM ABELL-1795

We have observed the rich cluster Abell 1795 for 90,000 s, using the d eep survey telescope aboard the Extreme-Ultraviolet Explorer, with the Lex/B (69-190 eV) passband filter Very luminous emission was detected , with a marked softening of the spectrum toward the limiting sensitiv ity radius of 10' (similar to 0.67 Mpc, assuming here and thereafter a Hubble constant of 75 km s(-1) Mpc(-1)), where the EUV intensity is 6 times higher than that expected from the low-energy tail of the therm al X-ray emission, and the resulting EUV luminosity (a model-independe nt quantity) exceeds that of the X-ray band. The consequence of a ther mal model interpretation is the existence of a warm (sub-MK) intraclus ter gas that is dynamical (cooling times less than or equal to 10(-4) of a Hubble time) and that contains a significant fraction, perhaps al l, of the total missing mass of the cluster. Alternative interpretatio ns of the data also invoke assumptions that have significant ramificat ions in our understanding of clusters.