Arecibo << `ahr` uh SEE boh >> Observatory is a former astronomical observatory in Puerto Rico, 50 miles (80 kilometers) west of San Juan. When the observatory opened in 1963, it had the world’s most powerful radio telescope. A radio telescope collects and measures radio waves given off by objects in space. In 2020, the telescope was decommissioned (retired) after two breaks in cables caused the structure to collapse.
Arecibo’s dish (bowl-shaped reflector) was one of the largest in the world. The dish, built into a basin-shaped valley, was 1,000 feet (305 meters) in diameter. It focused radio waves onto receivers that hung above it. The waves came from such distant objects as pulsars, rapidly spinning stars whose waves arrive on Earth as regular pulses. Arecibo astronomers discovered the first binary pulsar (pulsar in orbit around a companion star) in 1974. In the 1990’s, astronomers at the observatory discovered the first exoplanets. An exoplanet is a planet that orbits a star other than the sun. Also in the 1990’s, Arecibo astronomers detected ice at the poles of Mercury.
In 1996, special mirrors were added to sharpen the telescope’s focus. These additional mirrors hung with the radio receivers inside a helmetlike dome above the dish. Astronomers were able to track an object for several hours by continually repositioning the hanging mirrors. The telescope was also used as a giant radar system to map the surfaces of planets, comets, and asteroids. In addition, scientists used the telescope to study the regions of Earth’s atmosphere that make up the ionosphere. These regions have many ions (electrically charged atoms and groups of atoms).
After the main telescope was decommissioned, scientists continued to use the observatory’s smaller radio telescope and lidar instruments for research in astronomy and atmospheric science. Lidar is a technology that uses laser light to detect and locate moving or fixed objects. Regular research ceased in 2023 when the observatory ran out of funding. Researchers then worked to organize a complete collection of historical data from the decommissioned telescope so that scientists around the world could use it for their work.
See also National Science Foundation; Telescope (Radio and microwave telescopes).
