6522 Aci
Shape model of Aci from its lightcurve
Discovery [1]
Discovered byE. F. Helin
Discovery sitePalomar Obs.
Discovery date9 July 1991
Designations
(6522) Aci
PronunciationItalian: [ˈaːtʃi]
Named after
Italian Jaci river at Acireale
(Acis and Galatea)[2]
1991 NQ · 1990 BH4
main-belt [1][3] · Phocaea [4][5]
Orbital characteristics [3]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc27.36 yr (9,995 days)
Aphelion2.8595 AU
Perihelion1.9107 AU
2.3851 AU
Eccentricity0.1989
3.68 yr (1,345 days)
68.743°
0° 16m 3.36s / day
Inclination22.109°
294.45°
314.18°
Physical characteristics
Mean diameter
5.65 km (calculated)[4]
6.125±0.119 km km[6][7]
7.6921±0.0017 h[8]
0.23 (assumed)[4]
0.392±0.029[6][7]
S (family-based)[5][4]
12.7[6] · 13.0[3] · 13.003±0.005 (R)[8] · 13.1[1] · 13.45[4]

    6522 Aci (prov. designation: 1991 NQ) is an elongated Phocaea asteroid from the inner regions of the asteroid belt. It was discovered on 9 July 1991, by American astronomer Eleanor Helin at Palomar Observatory in California, United States.[1] The likely stony S-type asteroid has a rotation period of 5.65 hours and measures approximately 6 kilometers (3.7 miles) in diameter. It was named for the Jaci river at Acireale in Italy, and refers to the myth of Acis and Galatea.

    Orbit and classification

    Aci is a member of the Phocaea family (701),[5] a relatively small group of stony asteroids with similar orbital characteristics. It orbits the Sun in the inner main-belt at a distance of 1.9–2.9 AU once every 3 years and 8 months (1,345 days). Its orbit has an eccentricity of 0.20 and an inclination of 22° with respect to the ecliptic.[3] In January 1990, the asteroid was first observed as 1990 BH4 at the German Karl Schwarzschild Observatory, extending the body's observation arc by 17 months prior to its official discovery observation at Palomar.[1]

    Naming

    This minor planet was named for the Jaci river near Acireale, southeast of Mount Etna in Sicily, Italy. Other towns and villages along the river, such as Aci Castello, Aci Trezza, and Aci Sant'Antonio, were also honored.[2] The river's name refers to the myth Acis and Galatea from Greek mythology, which is about a young Sicilian shepherd, who was killed by the jealous cyclops Polyphemus, because of his love for the sea nymph Galatea. The minor planet 74 Galatea is named after this Nereid.[2] The approved naming citation was published by the Minor Planet Center on 26 October 1996 (M.P.C. 28090).[9]

    Physical characteristics

    Rotation period

    In September 2010, a rotational lightcurve of Aci was obtained from photometric observations taken at the Palomar Transient Factory in California. Lightcurve analysis gave a rotation period of 7.6921 hours with a brightness variation of 0.68 magnitude (U=2).[8]

    Diameter and albedo

    According to the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Aci measures 6.1 kilometers in diameter and its surface has a high albedo of 0.39,[6][7] while the Collaborative Asteroid Lightcurve Link assumes an albedo of 0.23 – which derives from 25 Phocaea, namesake and largest member of this orbital family – and calculates a diameter of 5.7 kilometers with an absolute magnitude of 13.45.[4]

    References

    1. 1 2 3 4 5 "6522 Aci (1991 NQ)". Minor Planet Center. Retrieved 28 April 2016.
    2. 1 2 3 Schmadel, Lutz D. (2007). "(6522) Aci". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 539. doi:10.1007/978-3-540-29925-7_5924. ISBN 978-3-540-00238-3.
    3. 1 2 3 4 "JPL Small-Body Database Browser: 6522 Aci (1991 NQ)" (2017-06-06 last obs.). Jet Propulsion Laboratory. Archived from the original on 18 September 2020. Retrieved 21 June 2017.
    4. 1 2 3 4 5 6 "LCDB Data for (6522) Aci". Asteroid Lightcurve Database (LCDB). Retrieved 28 April 2016.
    5. 1 2 3 "Asteroid 6522 Aci – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
    6. 1 2 3 4 Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 28 April 2016.
    7. 1 2 3 Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 5 December 2016.
    8. 1 2 3 Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 28 April 2016.
    9. ↑ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 28 April 2016.
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