Arecibo Observatory in the context of Five-hundred-meter Aperture Spherical Telescope

Arecibo (/ˌærəˈsiːboʊ/; Spanish pronunciation: [aɾeˈsiβo]) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about 50 miles (80 km) west of San Juan, the capital city. Arecibo is the largest municipality in Puerto Rico by area, and it is the core city of the Arecibo Metropolitan Statistical Area and part of the greater San Juan–Bayamón, PR Combined Statistical Area. It is spread over 18 barrios and Arecibo Pueblo (the downtown area and the administrative center of the city). Its population in 2020 was 87,754.

The Arecibo Observatory, which housed the Arecibo telescope, the world's largest radio telescope until July 2016, is located in the municipality. The Arecibo telescope collapsed on December 1, 2020. Arecibo is the seat of the Roman Catholic Diocese of Arecibo.

101955 Bennu (provisional designation 1999 RQ₃₆) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the second highest cumulative rating on the Palermo scale. It has a cumulative chance of around 1-in-1,750 of impacting Earth between 2178 and 2290 with the greatest risk being on 24 September 2182. It is named after Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth.

101955 Bennu has a mean diameter of 490 m (1,610 ft; 0.30 mi) and has been observed extensively by the Arecibo Observatory planetary radar and the Goldstone Deep Space Network.

The Arecibo Telescope was a 305 m (1,000 ft) spherical reflector radio telescope built into a natural sinkhole at the Arecibo Observatory located near Arecibo, Puerto Rico. A cable-mounted, steerable receiver and several radar transmitters for emitting signals were mounted 150 m (492 ft) above the dish. Completed in November 1963, the Arecibo Telescope was the world's largest single-aperture telescope for 53 years, until it was surpassed in July 2016 by the Five-hundred-meter Aperture Spherical Telescope (FAST) in Guizhou, China. Decommissioning the Arecibo Telescope was announced in November 2020, and the telescope collapsed in December 2020.

The Arecibo Telescope was primarily used for research in radio astronomy, atmospheric science, and radar astronomy, as well as for programs that search for extraterrestrial intelligence (SETI). Scientists wanting to use the observatory submitted proposals that were evaluated by independent scientific referees. NASA also used the telescope for near-Earth object detection programs. The observatory, funded primarily by the National Science Foundation (NSF) with partial support from NASA, was managed by Cornell University from its completion in 1963 until 2011, after which it was transferred to a partnership led by SRI International. In 2018, a consortium led by the University of Central Florida assumed operation of the facility.

The University of Puerto Rico at Arecibo (UPRA or UPR Arecibo) is a public college in Arecibo, Puerto Rico. It is part of the University of Puerto Rico. UPR-Arecibo was previously the Colegio Regional de Arecibo (CRA, 'Arecibo Regional College') and Colegio Universitario Tecnológico de Arecibo (CUTA, 'Arecibo Technological University College').

The college is located in the north of the island, next to the largest pharmaceutical and biotechnology complex in the Caribbean, agricultural areas of intense commercial activity and near the site of the Arecibo Observatory. It is accredited by the Middle States Association of Colleges and Schools.

Professor Abel Méndez is a planetary astrobiologist and Director, at the University of Puerto Rico at Arecibo. His research focuses on the habitability of potentially habitable exoplanets. Méndez is also a NASA MIRS Fellow with research experience at NASA, and the Arecibo Observatory.

He is best known for being one of the scientists who developed the Earth Similarity Index, a proposed characterization of how similar a planetary-mass object or natural satellite is to Earth.

270 Anahita is a stony S-type Main belt asteroid. It was discovered by C. H. F. Peters on October 8, 1887, in Clinton, New York, and was named after the Avestan divinity Aredvi Sura Anahita.

In 2001, the asteroid was detected by radar from the Arecibo Observatory at a distance of 0.92 AU. The resulting data yielded an effective diameter of 47 ± 7 km.

4337 Arecibo (prov. designation: 1985 GB) is a binary asteroid in the outer regions of the asteroid belt, approximately 24 kilometers (15 miles) in diameter. It was discovered on 14 April 1985, by American astronomer Edward Bowell at the Anderson Mesa Station near Flagstaff, Arizona, in the United States. It was named after the Arecibo Observatory in Puerto Rico. It has a relatively large minor-planet moon that was discovered in stellar occultation observations by David Gault and Peter Nosworthy in May 2021, distinguishing it as the first asteroid moon discovered and confirmed solely using the occultation method.

2017 YE₅ is a binary pair of asteroids of approximately equal size and mass, each about 0.9 km (0.56 mi) in diameter. Classified as a near-Earth asteroid and potentially hazardous object of the Apollo group, 2017 YE₅ was discovered by amateur astronomer Claudine Rinner at the Oukaïmeden Observatory on 21 December 2017. On 21 June 2018, the pair of asteroids passed within 15.5 lunar distances or approximately 6 million km (3.7 million mi) from Earth. During the close encounter, 2017 YE₅ was resolved in high detail by concurrent radar observations by the Arecibo and Green Bank observatories, along with individual observations by the Goldstone Solar System Radar. 2017 YE₅ is likely an extinct or dormant comet due to its distant elliptical orbit and dark red surface.