| Discovery[1] | |
|---|---|
| Discovered by | Edward L. G. Bowell |
| Discovery site | Anderson Mesa Stn. |
| Discovery date | 14 April 1985 |
| Designations | |
| (4337) Arecibo | |
Named after | Arecibo Observatory[2] |
| 1933 HE · 1979 FR3 1979 HG2 · 1985 GB | |
| Orbital characteristics[1] | |
| Epoch 9 August 2022 (JD 2459800.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 88.42yr (32,295 d) |
| Earliestprecovery date | 24 April 1933 |
| Aphelion | 3.5626AU |
| Perihelion | 2.9702 AU |
| 3.2664 AU | |
| Eccentricity | 0.0907 |
| 5.90 yr (2,156 d) | |
| 104.049° | |
| 0° 10m 1.041s / day | |
| Inclination | 2.2131° |
| 41.175° | |
| 183.07° | |
| Physical characteristics[3]: 3 | |
| |
| Mass | |
Meandensity | 1.2 g/cm3 (primary)[b] |
| 32.974 h (synchronous) | |
| 27°±3°[3]: 3 | |
| 267°±6°[3]: 3 | |
| 63°±3°[3]: 3 | |
| 0.077±0.004[5][1] 0.06±0.02[6] | |
 | This article needs to beupdated. The reason given is:New mass, density, and orbit determination byLiu et al. (2024). Please help update this article to reflect recent events or newly available information.(January 2026) |
4337 Arecibo is abinary asteroid in the outer regions of theasteroid belt, approximately 24 kilometers (15 miles) in diameter. It was discovered on 14 April 1985, by American astronomerEdward Bowell at theAnderson Mesa Station near Flagstaff, Arizona, in the United States. It was named after theArecibo Observatory in Puerto Rico.[2] It has a relatively largeminor-planet moon that was discovered instellar 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.[7]
This asteroid was discovered by American astronomerEdward Bowell while measuring a pair of images taken with theLowell Observatory's 0.33-meterastrograph on 14 April 1985, located at theAnderson Mesa Station near Flagstaff, Arizona, in the United States.[8]: 71 The discovery observations were published by theMinor Planet Center on 4 May 1985.[8]: 71 In September 1985, astronomersKiichirō Furukawa andLutz D. Schmadel both identified the asteroid in prediscovery observations from March and April 1979, while Furukawa independently found earlier prediscovery observations from April 1933.[9]: 59 With these prediscovery observations linked, the asteroid's orbit was significantly improved and eventually received its permanentminor planet number of 4337 from the Minor Planet Center on 11 January 1990.[10]: 90
The asteroid was named after theArecibo Observatory in Puerto Rico, home to the world's largestfilled-aperature radio telescope in the 20th century. The name was proposed byradar astronomerSteven J. Ostro, in recognition of the observatory's indispensable contributions to the characterization of Solar System bodies including asteroids.[2] The official naming citation was published by the Minor Planet Center on 8 June 1990.[11]: 155
On 19 May 2021, twoamateur 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.[7][4]: 3 Each observed the stellar occultation usinghigh-speed video cameras attached to their 30-cm aperture telescopes at their home observatories, separated from each other by 0.7 km (0.43 mi) across (perpendicular) and 18 km (11 mi) along (parallel) the path of Arecibo's shadow across Earth.[4]: 3 They detected a two-second-long occultation starting at 17:58UTC, but then unexpectedly detected a secondary, shorter-duration occultation three seconds later.[7][4]: 3 The observed drop in the star's brightness for both events was much greater than would be expected for adouble star with one component occulted, leading Gault and Nosworthy to the conclusion that the secondary occultation was more likely caused by anatural satellite orbiting Arecibo.[4]: 3
Several days after the discovery of Arecibo's satellite, other occultation astronomers were alerted to follow up in another occultation event by Arecibo over North America on 9 June 2021.[7] Richard Nolthenius and Kirk Bender, separated from each other by 8.2 km (5.1 mi) across and 8 km (5.0 mi) along Arecibo's shadow path, successfully observed the 9 June 2021 occultation from central California.[4]: 3 As Arecibo passed in front of a magnitude 12.0 star, they detected the primary two-second-long occultation starting at 10:58 UTC and then the satellite make a secondary occultation three seconds later, confirming the existence of Arecibo's satellite.[7][4]: 4 The satellite discovery and confirmation results from the May and June 2021 occultations were formally published byCentral Bureau for Astronomical Telegrams on 20 June 2021.[12] Discoverers Gault and Nosworthy recognize Arecibo's satellite as the first asteroid moon discovered by amateur astronomers and confirmed using the occultation method.[7][c]
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. Only 3 of the 5 successful sites reported positive detections (Nolthenius, Bender, and Christopher Kitting of CSU East Bay reported positives) with a single occultation; the other two had misses and did not detect the satellite. It is possible the satellite and main body were a blended image, given the close orbit later determined.[4]: 4
Arecibo orbits the Sun in theouter main-belt at a distance of 3.0–3.6 AU once every 5 years and 11 months (2,156 days;semi-major axis of 3.27 AU). Its orbit has aneccentricity of 0.09 and aninclination of 2° with respect to theecliptic.[1] Arecibo's orbit is similar to that of the large asteroid24 Themis, which indicates that Arecibo belongs to theThemis family (602), a very largefamily ofcarbonaceous asteroids that are believed to have originated as fragments from animpact event on Themis.[13]: 320
Because of its low orbital inclination, Arecibo is visible along the ecliptic atapparent magnitudes 16–18.[2] Arecibo is too faint to be seen with thenaked eye, even when at its peak brightness of magnitude 16 atopposition—a telescope of at least 60 cm (24 in) inaperture size is required to see it.[14]
Thespectral class of Arecibo is unknown, but it can be assumed to be a carbonaceousC-type,[15] similar to most members of the Themis family.[13]: 320 Like most members of the Themis family, Arecibo likely has a highlyporous internal structure with a low density below1.3 g/cm3, as indicated by its mass determined from the satellite's orbital motion.[16]: 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.[4] On the other hand,infraredthermal emission measurements by theJapan Aerospace Exploration Agency'sAkari andNASA'sWide-field Infrared Survey Explorer (WISE) determined smaller diameters of 17.6 and 19.7 km (10.9 and 12.2 mi), respectively, with correspondinggeometric albedos of 0.10 and 0.08.[15] The discrepancy between the occultation and infrared measurements may be caused by a highly flattened shape for both components of the Arecibo system; in this case the occultation-derived primary diameter would represent the maximum extent of its shape.[16]: 17 WISE's estimates for Arecibo'sabsolute magnitude range from 11.9 to 12.6, with an average of 12.4 assumed by the Collaborative Asteroid Lightcurve Link.[15] The Minor Planet Center andJet Propulsion Laboratory'sSmall-Body Database both determine an absolute magnitude of 12.5 based on visiblephotometry only.[2][1]
In July 2021, a preliminary rotationallightcurve of Arecibo was obtained from photometric observations by Swiss astronomerRaoul Behrend atGeneva Observatory in Switzerland.[17] Lightcurve analysis gave an approximaterotation period of32.85±0.38 hours with a brightness amplitude of 0.17magnitude (U=2).[15] High-precision photometry andastrometry from theGaia spacecraft confirmed this period and showed that it is equal to the satellite's orbital period, suggesting that the Arecibo primary is insynchronous rotation with the satellite's orbital period.[16]: 16
Based onGaia photometry, Arecibo's north pole points in the direction ofecliptic longitude 271° andecliptic latitude 68°.Gaia astrometry for the satellite's orbit yields a pole orientation of ecliptic longitude261°±3° and ecliptic latitude60°±3°, in agreement with the photometry-derived pole orientation.[16]: 16 This suggests theaxial tilt of Arecibo primary is aligned with the satellite's orbital inclination at 30° with respect to the ecliptic.[d]
| Discovery[12] | |
|---|---|
| Discovered by |
|
| Discovery date | 19 May 2021 |
| Orbital characteristics[16]: 16 | |
| Epoch 8 August 2014 04:51:48UTC (JD 2456877.70264) | |
| 46.8+1.8 −2.0 km | |
| Eccentricity | 0.06±0.04 |
| 32.9741±0.0004 h | |
| Inclination | 27°±3° wrtecliptic |
| 357°±6° | |
| 233°±44° | |
| Satellite of | 4337 Arecibo |
| Physical characteristics | |
| Mass | 0.2×1015 kg[3]: 3 |
Meandensity | 1.6 g/cm3 (primary)[b] |
Arecibo hosts a relatively largeminor-planet moon with a size about half its diameter, forming abinary system. This unnamed satellite orbits closely at an orbital radius of 50 km (31 mi) from the primary body of the Arecibo system, completing a full revolution in about 33 hours or 1.4 days.[16]: 16 It was discovered by Australian amateur astronomers David Gault and Peter Nosworthy while observing Areciboocculting a star on 19 May 2021, and was confirmed in another occultation on 9 June 2021.[7][c]
The observedangular separation between the satellite and primary body in the 19 May and 9 June 2021 occultations were25.5±1.0 and32.8±0.7milliarcseconds, respectively.[12][4] In July 2021, Nolthenius presented a preliminary analysis suggesting that the satellite's orbital radius should lie in the range of 100–293 km (62–182 mi), based on an assumed system density of1.9 g/cm3 and an outerorbital stability limit set byJupiter'sgravitational influence.[19]: 39 Because no photometric measurements of Arecibo's rotation period were available at that time, constraints on the satellite's orbital period were solely limited to the three occultations observed in 2021, which suggested periods of 20 days and its shorter-periodaliases of 10 days, 5 days, and 2.5 days.[19]: 39
On 13 June 2022, a team of European astronomers led by Paolo Tanga, on behalf of theEuropean Space Agency, published a proof-of-concept analysis of the Arecibo system using high-precision astrometry and photometry from theGaia mission, as part of its third data release.[20][16]: 16 They found that Arecibo exhibits periodic oscillations in brightness and position that are both compatible with a period of 32.972823 hours (1.3738676 d), consistent with earlier ground-based photometry from July 2021 and establishing the satellite's orbital period.[17][16]: 16 They determined a smaller orbital radius of 49.9 ± 1.0 km (31.01 ± 0.62 mi) and an inclination of30°±3° with respect to the ecliptic, precisely coinciding with the satellite's positions observed in the May and June 2021 occultations.[16]: 16 [d] Given the satellite's close proximity to the primary body and coincidence of brightness and position oscillation periods, the satellite is likely insynchronous orbit with the primary's rotation period.[16]: 16
The initial detection of the satellite in the 19 May 2021 occultation provided poor constraints on its size due to close spacing between the observers' sites.[12] The 9 June 2021 occultation proved to be more reliable with wider spacing between observer sites, providing a best-fit satellite diameter of 13 ± 1.5 km (8.08 ± 0.93 mi) for an assumed spherical shape for the satellite.[4]: 4 Given this diameter estimate, this makes the satellite about half the size of the primary body in the Arecibo system.[16]: 16
The satellite is massive enough to induce measurable positional wobbling of the Arecibo primary, although with an unexpectedly low amplitude of up to 2.7 milliarcseconds fromGaia's view, or 8.5% of the maximum observed angular separation between the satellite and primary.[16]: 16 This small positional wobbling of the Arecibo primary implies a very low satellite-to-primary mass ratio relative to the satellite-to-primary diameter ratio, which could either be explained by a highly flattened shape or a very low density for the satellite.[16]: 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.[16]: 17 In this case, the occultation-derived satellite diameter would represent its maximum shape extent and its minimum possible density would be1 g/cm3, which is expected for a highly porous asteroid of the Themis family.[16]: 17
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| Dwarf planet satellites of | ||
| Minor-planet moons | ||
| Ranked by size | ||