4765 Wasserburg

4765 Wasserburg (prov. designation: 1986 JN1) is a bright Hungaria asteroid, suspected binary system and asteroid pair from the innermost regions of the asteroid belt, approximately 3 kilometers (1.9 miles) in diameter. It was discovered on 5 May 1986, by American astronomer Carolyn Shoemaker at Palomar Observatory, and later named after geologist Gerald J. Wasserburg.[2][3]

4765 Wasserburg
Shape model of Wasserburg from its lightcurve
Discovery [1]
Discovered byC. Shoemaker
Discovery sitePalomar Obs.
Discovery date5 May 1986
Designations
(4765) Wasserburg
Named after
Gerald J. Wasserburg
(American geologist)[2]
1986 JN1 · 1983 EA1
1986 LF
main-belt (inner) [1] · Hungaria [3][4]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc33.15 yr (12,108 days)
Aphelion2.0621 AU
Perihelion1.8289 AU
1.9455 AU
Eccentricity0.0599
2.71 yr (991 days)
237.52°
0° 21m 47.52s / day
Inclination23.710°
76.546°
108.33°
Known satellites1 (suspected)[5][6]
Physical characteristics
Mean diameter
1.777±0.485 km[7][8]
3.82 km (calculated)[4]
3.6231±0.0005 h[5]
3.625±0.001 h[9]
3.62532±0.00002 h[lower-alpha 1]
3.626±0.005 h[lower-alpha 2]
3.6260±0.0005 h[10]
3.6280±0.0005 h[11]
3.664±0.003 h[12]
3.67±0.02 h (dated)[13]
0.4 (assumed)[4]
1.000±0.087[7][8]
E [4]
B–V = 0.852±0.043[14]
V–R = 0.456±0.023[14]
V–I = 0.813±0.040[14]
13.7[1][4] · 14.1[7]

    Orbit and classification

    Wasserburg is a bright member of the Hungaria family, which form the innermost dense concentration of asteroids in the Solar System. It orbits the Sun in the inner main-belt at a distance of 1.8–2.1 AU once every 2 years and 9 months (991 days). Its orbit has an eccentricity of 0.06 and an inclination of 24° with respect to the ecliptic.[1] It was first identified as 1983 EA1 at Palomar in 1983, extending the body's observation arc by 3 years prior to its official discovery observation.[3]

    Wasserburg forms an asteroid pair with (350716) 2001 XO105, and was part of Petr Pravec's sample study Formation of asteroid pairs by rotational fission, published in the journal Nature.[4][10]

    Naming

    This minor planet was named after American Gerald J. Wasserburg (1927–2016), who was a professor of geology and geophysics at Caltech in California. He was a pioneer of radiometric dating methods used in isotope geochemistry and was prominent for his accurate age determination measurements of moon rocks, which were instrumental for reconstructing the origin of the Moon and for the hypothesis of the Late Heavy Bombardment.[2] Wasserburg also carried out isotopic analyses of meteorites, developed a time scale for the formation and evolution of the Solar System, and contributed to the theory of nucleosynthesis.[2] The official naming citation was published on 27 June 1991 (M.P.C. 18464).[15]

    Physical characteristics

    Diameter and albedo

    According to preliminary results from the survey carried out by NASA's Wide-field Infrared Survey Explorer (WISE) with its subsequent NEOWISE mission, Wasserburg measures 1.777 kilometers in diameter and its surface has an outstandingly high albedo of 1.000,[7][8] while the Collaborative Asteroid Lightcurve Link assumes it to be an E-type asteroid, with albedo of 0.40 – derived from 434 Hungaria the family's namesake and most prominent member – and calculates a larger diameter of 3.82 kilometers with an absolute magnitude of 13.7.[4]

    Rotation period

    Between 2006 and 2014, several rotational lightcurves of Wasserburg were obtained from photometric observations by astronomers Brian Warner at his Palmer Divide Observatory (716), Petr Pravec at Ondřejov Observatory, and Julian Oey at Blue Mountains Observatory (E19). Best rated lightcurve analysis gave a well-defined rotation period between 3.6231 and 3.6280 hours with a brightness variation between 0.07 and 0.60 magnitude (U=3/3/3/3-).[5][9][10][11][lower-alpha 1][lower-alpha 2][lower-alpha 3] Due to the changing amplitude, Wasserburg is likely one of the more elongatedly shaped primary asteroids of all known smaller binaries with an diameter of less than 10 kilometers.[5]

    Satellite

    After being already recognized as an asteroid pair, American astronomer Brian Warner observed faint mutual eclipsing and occultation events in April 2013. After repeated lightcurve subtraction, he was able to show that Wasserburg is likely a binary system with a minor-planet moon orbiting it every 15.97 hours. Assuming a depth of 0.03 magnitude, he estimated a secondary-to-primary mean-diameter ratio of 0.16±0.02.[5] The Johnston's archive derives a diameter of 280±80 meters for the satellite, based on the primary diameter given by WISE.[6] A semi-major axis of 2.9 kilometers is also estimated for the moons orbit.[6] However, photometric observations taken in 2015, could not detect the presence of a satellite and Wasserburg remains only a suspected binary.[12]

    Notes
    1. Pravec (2010) web: rotation period 3.62532±0.00002 hours with a brightness amplitude of 0.59 mag. Quality code of 3. Summary figures at Collaborative Asteroid Lightcurve Link – CALL and Pravec, P.; Wolf, M.; Sarounova, L. (2010)
    2. Pravec (2013) web: rotation period 3.626±0.005 hours with a brightness amplitude of 0.25 mag. Quality code of 3. Summary figures at Collaborative Asteroid Lightcurve Link – CALL and Pravec, P.; Wolf, M.; Sarounova, L. (2013)
    3. lightcurve plot Modra-PDO (A) and lightcurve plot Modra-PDO (B) taken at Modra, PDO, by Kusnirak and Pravec, rotation period 3.62532±0.00002 hours with a brightness amplitude of 0.59 mag. Quality Code of 3. Time span: 3 January 2010 to 7 March 2010. lightcurve plot Warner Palmer Divide Observatory, Brian D. Warner (2010). rotation period 3.625±0.001 hours with a brightness amplitude of 0.60±0.02 mag.Quality Code = 3. Time span: 5 and 8 January 2010.

    References
    1. "JPL Small-Body Database Browser: 4765 Wasserburg (1986 JN1)" (2016-05-06 last obs.). Jet Propulsion Laboratory. Retrieved 4 July 2017.
    2. Schmadel, Lutz D. (2007). "(4765) Wasserburg". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 410. doi:10.1007/978-3-540-29925-7_4671. ISBN 978-3-540-00238-3.
    3. "4765 Wasserburg (1986 JN1)". Minor Planet Center. Retrieved 18 April 2017.
    4. "LCDB Data for (4765) Wasserburg". Asteroid Lightcurve Database (LCDB). Retrieved 18 April 2017.
    5. Warner, Brian D.; Stephens, Robert D. (October 2013). "One New and One Suspected Hungaria Binary Asteroid" (PDF). Minor Planet Bulletin. 40 (4): 221–223. Bibcode:2013MPBu...40..221W. ISSN 1052-8091. Retrieved 18 April 2017.
    6. Johnston, Robert (21 September 2014). "(4765) Wasserburg". johnstonsarchive.net. Retrieved 18 April 2017.
    7. 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.
    8. 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 18 April 2017.
    9. Warner, Brian D. (July 2010). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory: 2009 December - 2010 March" (PDF). Minor Planet Bulletin. 37 (3): 112–118. Bibcode:2010MPBu...37..112W. ISSN 1052-8091. Retrieved 18 April 2017.
    10. Pravec, P.; Vokrouhlický, D.; Polishook, D.; Scheeres, D. J.; Harris, A. W.; Galád, A.; et al. (August 2010). "Formation of asteroid pairs by rotational fission". Nature. 466 (7310): 1085–1088. arXiv:1009.2770. Bibcode:2010Natur.466.1085P. doi:10.1038/nature09315. PMID 20740010.
    11. Oey, Julian (January 2016). "Lightcurve Analysis of Asteroids from Blue Mountains Observatory in 2014" (PDF). Minor Planet Bulletin. 43 (1): 45–51. Bibcode:2016MPBu...43...45O. ISSN 1052-8091. Retrieved 18 April 2017.
    12. Warner, Brian D. (April 2015). "Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2014 October-December" (PDF). Minor Planet Bulletin. 42 (2): 108–114. Bibcode:2015MPBu...42..108W. ISSN 1052-8091. Retrieved 18 April 2017.
    13. Warner, Brian D. (September 2007). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory - December 2006 - March 2007" (PDF). Minor Planet Bulletin. 34 (3): 72–77. Bibcode:2007MPBu...34...72W. ISSN 1052-8091. Retrieved 18 April 2017.
    14. Ye, Q.-z. (February 2011). "BVRI Photometry of 53 Unusual Asteroids". The Astronomical Journal. 141 (2): 8. arXiv:1011.0133. Bibcode:2011AJ....141...32Y. doi:10.1088/0004-6256/141/2/32. Retrieved 18 April 2017.
    15. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 18 April 2017.
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