Today marks the third anniversary of the launch of the Advanced Satellite for Cosmology and Astrophysics (ASCA; renamed from Astro D when launched). ASCA , seen here superposed on galaxy M31 , is a Japanese satellite for which NASA has provided some scientific equipment. ASCA carries four large-area X-ray telescopes. At the focus of two of the telescopes is a Gas Imaging Spectrometer ( GIS ), while a Solid-state Imaging Spectrometer ( SIS ) is at the focus of the other two. ASCA has provided recent evidence that high energy cosmic rays are formed in the expanding gas from a supernova . During ASCA's three years of operation, it has also yielded valuable data on quasars , supernova remnants , dwarf novae , pulsars , clusters of galaxies , and the mysterious X-ray background radiation that appears to come from all directions.
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Credit: ISAS, NASA