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Why are space observatories important? The answer concerns twinkling stars in the night sky. To reach telescopes on Earth, light from distant objects has to penetrate Earth’s atmosphere. Although the sky may look clear, the gases that make up our atmosphere cause problems for astronomers. These gases absorb the majority of radiation emanating from celestial bodies so that it never reaches the astronomer’s telescope. Radiation that does make it to the surface is distorted by pockets of warm and cool air, causing the twinkling effect. In spite of advanced computer enhancement, the images finally seen by astronomer sare incomplete.

Observatories located in space collect data free from the distortion of Earth’s atmosphere. Space observatories contain advanced, highly sensitive instruments, such as telescopes (the Hubble Space Telescope and the Chandra X-ray Observatory) and detectors (the Compton Gamma Ray Observatory and Chandra X-ray Observatory), that allow scientists to study radiation from neighboring planets and galaxies billions of light years away. By analyzing the spectrum of radiation emitted or absorbed by an object, scientists can determine the temperature, chemical composition, and motion of an object. The light from these distant celestial bodies may take billions of years to reach the observatories, so scientists can actually look into the past and learn what was happening in the universe when it was young. The data that these observatories gather help scientists

determine how stars and galaxies are formed and provide insights into the origin and evolution of the universe.

NASA, in conjunction with other countries’ space agencies, commercial companies, and the international community, has built observatories such as the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Chandra X-ray Observatory to find the answers to numerous questions about the universe. With the capabilities the Space Shuttle provides, scientist now have the means for deploying these observatories from the Shuttle’s cargo bay directly into orbit.

Each of the three spacecraft represented by models here are named for noted astronomers in the fields of optical and highenergy astronomy. The Hubble Space Telescope is named for Edwin Hubble. The Compton Gamma Ray Observatory is named for Arthur Holly Compton, and the Chandra X-ray Observatory is named for Subrahmanyan Chandrasekhar. “Chandra” was a nickname used by Chandrasekhar. Assign some students the task of researching these three astronomers and their accomplishments. For more information about the NASA Great Observatories, visit the Office of Space Science web site at http://spacescience.nasa.gov/missions/index.htm