... Tonight's Sky . ... NASA satellites find high-energy surprises in т??constantт?? Crab Nebula . ... The combined data from several NASA satellites has astonished astronomers by revealing unexpected changes from the Crab Nebula (M1), once thought to be the steadiest high-energy source in the sky . т??For 40 years, most astronomers regarded the Crab as a standard candle,т?? said Colleen Wilson-Hodge, an astrophysicist at NASAт??s Marshall Space Flight Center in Huntsville, Alabama ...