A pulsar system called 4U 0115 63 was the object of the first "hard X-ray" image of a celestial object. This is a false-color image showing X-ray intensity from white (brightest) to blue (faintest). 4U 0115 63 is a two-star system, in which a pulsar about 20 miles across orbits a star larger than our Sun.
From our distant vantage point, the system appears as a single point. The structure seen here -- glowing in X-rays at the 20-40 kilo-electron-volt energy level, thousands of times more energetic than optical light -- is not visible to optical telescopes. X-rays are generated when gas from the Sun-like star falls towards and onto the pulsar, attracted by the dense pulsars strong gravity.
Other X-ray instruments, such as NASA's Chandra X-ray Observatory, turn lower-energy "soft" X-rays into visible images. To capture elusive hard X-rays, scientists from the United States and Japan built an instrument with new types of mirrors and detectors. This instrument, called InFOCuS (International Focusing Optics Collaboration for u-Crab Sensitivity), is a test bed for a proposed NASA satellite mission called Constellation-X.
Credit: NASA - Nagoya University