4337 Arecibo
[9] This asteroid was discovered by American astronomer Edward Bowell while measuring a pair of images taken with the Lowell Observatory's 0.33-meter astrograph on 14 April 1985, located at the Anderson Mesa Station near Flagstaff, Arizona, in the United States.
The name was proposed by radar astronomer Steven J. Ostro, in recognition of the observatory's indispensable contributions to the characterization of Solar System bodies including asteroids.
[13]: 155 On 19 May 2021, two amateur astronomers, David Gault and Peter Nosworthy, observed Arecibo passing in front of a magnitude 13.6 star and blocking out its light from New South Wales, Australia.
[14] Discoverers Gault and Nosworthy recognize Arecibo's satellite as the first asteroid moon discovered by amateur astronomers, and confirmed using the occultation method.
[9][a] On 30 June 2021, astronomers across the United States prepared for another occultation by Arecibo to further follow up on its satellite, but majority of them experienced technical difficulties and unfavorable weather conditions, resulting in only 5 out of 15 different sites making successful observations.
[15]: 320 Like most members of the Themis family, Arecibo likely has a highly porous internal structure with a low density below 1.3 g/cm3, as indicated by its mass determined from the satellite's orbital motion.
[5]: 17 Based on occultation observations from 9 June 2021, the primary body of the Arecibo system measures 24.4 ± 0.6 km (15.16 ± 0.37 mi) in diameter, assuming that it has a spherical shape.
[3] The Minor Planet Center and Jet Propulsion Laboratory's Small-Body Database both determine an absolute magnitude of 12.5 based on visible photometry only.
[2][1] In July 2021, a preliminary rotational lightcurve of Arecibo was obtained from photometric observations by Swiss astronomer Raoul Behrend at Geneva Observatory in Switzerland.
[6][5]: 16 They determined a smaller orbital radius of 49.9 ± 1.0 km (31.01 ± 0.62 mi) and an inclination of 30°±3° with respect to the ecliptic, precisely coinciding with the satellite's positions observed in the May and June 2021 occultations.
[5]: 17 Tanga and collaborators favor the high flattening scenario as it yields more realistic density values and can explain the infrared underestimation of the primary's diameter.
[5]: 17 In this case, the occultation-derived satellite diameter would represent its maximum shape extent and its minimum possible density would be 1 g/cm3, which is expected for a highly porous asteroid of the Themis family.
