What Is an Astronomy Observatory?

An astronomy observatory is a facility that houses one or more telescopes used to observe electromagnetic radiation (light) in space. Astronomers study this light to gain insights into the structure and evolution of celestial objects. An observatory’s equipment can collect information from all parts of the electromagnetic spectrum, from radio waves to visible light. A specialized observatory can also gather information on gamma rays and neutrinos. Some observatories have domes that rotate to provide views of different areas of the sky. Others are completely portable.

A telescope’s ability to capture and analyze data is its key to advancing human knowledge of the universe. Early optical telescopes were limited in their light-gathering capabilities and were only capable of seeing in the visible spectrum. The first major astronomical observatories were established in the 18th and 19th centuries, and were based at Greenwich (London), Paris, Cape Town, and Washington, D.C. By timing the passage of stars as they swept past the observatory along the local meridian, these observatories were able to improve the accuracy of position measurements for celestial objects from minutes of arc to less than a tenth of second of arc.

The ability to see regions of the electromagnetic spectrum besides visible light was further enhanced with the advent of the space age, which allowed satellites to orbit above Earth’s absorbing and distorting atmosphere. Since the 1960s, astronomers have developed observatories that can see in a variety of wavelengths including gamma rays (Compton Gamma Ray Observatory and Fermi Gamma-ray Space Telescope), X-rays (Chandra X-ray Observatory and XMM-Newton), ultraviolet radiation (International Ultraviolet Explorer and Chandra X-ray Observatory) and infrared radiation (Spitzer Space Telescope, Hubble Space Telescope and the James Webb Space Telescope).

To make the most of a telescope’s capabilities, it is important to be in a location that has good atmospheric conditions. This includes a high elevation to get away from light pollution, and clear weather that allows the telescope to “see” through clouds that could obscure objects being studied. The clarity of the atmosphere, called transparency, and the stability of the light that reaches the telescope, referred to as “seeing,” are important factors for astronomical observation.

The success of astronomical observatories in space has led to plans for even larger and more complex space telescopes that will be able to see deeper into the universe than previous observatories and to observe light from much more distant objects. For example, NASA’s Next Generation Space Telescope will have a mirror 6.5 meters (21.3 feet) across to allow it to study objects that are much more faint and far away. Another observatory currently in development is the Space Infrared Telescope Facility, which will probe the universe at infrared wavelengths that are longer and less energetic than those seen with visible light. The development of this observatory will advance scientific understanding of how galaxies and stars form in the early universe, and may reveal clues to the origins of life. In addition to constructing and launching these large observatories, NOAO has contributed to the advancement of technology that has changed the way astronomers work by developing the Image Reduction and Analysis Facility (IRAF) software, which simplifies the process of collecting and analyzing electronic data from telescopes.