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In orbit about 380 miles (610 kilometers) above the earth, the Hubble Space Telescope views the heavens without looking through the earth's atmosphere. The atmosphere bends light due to a phenomenon known as diffraction, and the atmosphere is constantly moving. This combination of diffraction and movement causes starlight to jiggle about as it passes through the air, and so stars appear to twinkle. Twinkling blurs images seen through ground-based telescopes. Because an orbiting telescope is above the atmosphere, it can produce pictures in much finer detail than a ground-based telescope can.
This false-color image taken by the Hubble Space Telescope using infrared light shows Uranus's rings and clouds. The different colors in the image represent different atmospheric conditions.
The Hubble Space Telescope can also observe ultraviolet and infrared light that is blocked by the atmosphere. These forms of light, like visible light, are electromagnetic radiation. The wavelength (distance between successive wave crests) of ultraviolet light is shorter than that of visible light. Infrared light has longer wavelengths than visible light. Ultraviolet light comes from highly energetic processes, such as the formation of disks around black holes and exploding stars. Infrared light provides information about cooler, calmer events, such as the formation of dust clouds around new stars.
The United States space agency, the National Aeronautics and Space Administration (NASA), operates the Hubble Space Telescope in cooperation with the European Space Agency (ESA). The telescope is controlled by radio commands relayed from NASA's Goddard Space Flight Center in Greenbelt, Maryland. Astronomers tell the telescope where to point, and computer -- driven instruments aboard the telescope record the resulting observations. The telescope transmits the data by radio to astronomers on the ground.
The Hubble Space Telescope has two kinds of instruments: (1) imagers, which take pictures; and (2) spectrographs, which analyze light. Imagers are electronic detectors called charge -- coupled devices (CCD's). The CCD's convert light into electronic signals, which an on -- board computer records and sends to the ground.
A spectrograph, like a prism, spreads light into its component colors, much as water droplets spread sunlight into a rainbow. The resulting band of light is called a spectrum (plural spectra). Using spectrographic data from the Hubble Space Telescope, astronomers can determine the composition of stars and galaxies--measuring, for example, the amounts of hydrogen, carbon, and other chemical elements in them.
