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study of volcanoes, study of earthquakes, volcanology, seismology, celestial objects

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Observatory, building from which astronomers observe celestial objects such as planets, stars, and galaxies. The main instrument in an astronomical observatory is usually a telescope, a device that gathers light from distant objects and makes them appear larger than they do with the naked eye.

Scientists keep sophisticated instruments such as telescopes, cameras, computers, and other electronic devices inside observatories to protect them from moisture, sudden temperature changes, and other dangers caused by outside weather. Astronomers use this equipment to analyze light beams coming from space and celestial bodies. This light helps them study the physical and chemical properties of the objects.

People also use the word observatory to refer to the complex of buildings where astronomers go to carry out research. One such complex, Kitt Peak National Observatory west of Tucson, Arizona, is a complete mountaintop city. At Kitt Peak, astronomers from around the world have access to dozens of telescopes, electronic and machine shops, and laboratories. Kitt Peak also includes a library, dormitories, a cafeteria, and even has its own water supply, electrical generators, and fire-fighting equipment.

Astronomers build observatories in places where Earth’s atmosphere creates the least amount of interference between the telescope and space. Interference occurs when particles in the atmosphere, such as water molecules, reflect and distort light. Astronomers look for sites where the weather is clear and the air is calm and dry. Most modern observatories are on high mountaintops far from cities. At high altitudes, Earth’s atmosphere is thinner, allowing astronomers to see the universe more clearly. It is also important that the nighttime sky at an observatory site be free from city lights or interference from human-made radio sources. Artificial light and radio sources can pollute telescope observations with unwanted signals.

Astronomical instruments are also carried into orbit around Earth, where the atmosphere does not interfere with their observations. Observatories such as the Hubble Space Telescope orbit far above Earth and can see the cosmos more clearly than any ground-based instrument in operation. These observatories are usually operated remotely by scientists on the ground.

Other fields of science, such as the study of volcanoes (volcanology), the study of earthquakes (seismology), and the study of Earth’s weather (meteorology), also use buildings called observatories to house their equipment and to carry out research. However, the term observatory usually means a place of astronomical observations.


Mammana, Dennis L., B.S., M.S.

Resident Astronomer, Reuben H. Fleet Science Center. Author of "Other Suns. Other Worlds?", "The Night Sky: An Observer's Guide", and "Star Hunters".

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