989 Schwassmannia

989 Schwassmannia (prov. designation: A922 WD or 1922 MW) is a stony background asteroid and a slow rotator from the central regions of the asteroid belt, approximately 12.5 kilometers (7.8 miles) in diameter. It was discovered on 18 November 1922, by astronomer Friedrich Karl Arnold Schwassmann at the Bergedorf Observatory in Hamburg, Germany.[1] The bright S/T-type asteroid has a long rotation period of 107.9 hours.[4] It was named after the discoverer himself.[2]

989 Schwassmannia
Discovery [1]
Discovered byA. Schwassmann
Discovery siteBergedorf Obs.
Discovery date18 November 1922
Designations
(989) Schwassmannia
Pronunciation/ʃwæsˈmæniə, ʃvɑːs-/
Named after
Friedrich Karl Arnold Schwassmann
(discoverer himself)[2]
A922 WD · 1922 MW
1935 UE · 1935 UF
main-belt [1][3] · (middle)
background [4]
Orbital characteristics [3]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 0
Observation arc96.49 yr (35,244 d)
Aphelion3.3261 AU
Perihelion1.9915 AU
2.6588 AU
Eccentricity0.2510
4.34 yr (1,584 d)
83.840°
0° 13m 38.28s / day
Inclination14.700°
243.40°
165.73°
Physical characteristics
Mean diameter
  • 12.20±1.12 km[5]
  • 12.630±0.124 km[6]
  • 12.86±0.8 km[7]
107.85±0.01 h[8][9]
  • 0.2035±0.027[7]
  • 0.226±0.043[5]
  • 0.306±0.064[6]
11.8[1][3]

    Orbit and classification

    Schwassmannia is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[11] It orbits the Sun in the central main-belt at a distance of 2.0–3.3 AU once every 4 years and 4 months (1,584 days; semi-major axis of 2.66 AU). Its orbit has an eccentricity of 0.25 and an inclination of 15° with respect to the ecliptic.[3] The body's observation arc begins at the Heidelberg Observatory on 12 November 1922, just 6 days prior to its official discovery observation at the Bergedorf Observatory in Hamburg.[1]

    Naming

    This minor planet was named after its discoverer, German astronomer Arnold Schwassmann (1870–1964), who discovered four comets and 22 asteroids in total (including this one). Schwassmann worked at the Potsdam (Berlin) and Hamburg–Bergedorf observatories. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 94).[2]

    Physical characteristics

    In the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Schwassmannia is an S-type and T-type asteroid, respectively.[4][10]

    Rotation period

    In November 2013, a rotational lightcurve of Schwassmannia was obtained from photometric observations by astronomers Vladimir Benishek at Sopot Astronomical Observatory (K90), Serbia, American Frederick Pilcher at his Organ Mesa Observatory (G50), New Mexico, and Luis Martinez at Lenomiya Observatory (H13) at Casa Grande in Arizona. Lightcurve analysis gave a well-defined rotation period of 107.85±0.01 hours with a brightness amplitude of 0.35±0.02 magnitude (U=3).[8][9] Alternative observations with a lower rated quality by Robert Stephens at the Center for Solar System Studies (U81) in September 2013 gave a period of 120.3±1 hours (U=2).[12][lower-alpha 1] The results supersede an earlier, tentative observation by Italian Federico Manzini at the Sozzago Astronomical Station (A12) from October 2004, with an incorrect period 4.5 hours (U=1).[4][13]

    Diameter and albedo

    According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telescope, Schwassmannia measures between 12.20±1.12 and 12.86±0.8 kilometers in diameter and its surface has a high albedo between 0.20 and 0.31.[5][6][7] The Collaborative Asteroid Lightcurve Link adopts the result from IRAS, that is, an albedo of 0.2037 and a diameter of 12.86 kilometers based on an absolute magnitude of 11.8.[8]

    Notes
    1. Lightcurve plot of (989) Schwassmannia by Robert Stephens with a rotation period 120.3±1 hours and a brightness amplitude of 0.39±0.05 mag. Quality code for this lightcurve is "2" at the LCDB. Summary figures at the Center for Solar System Studies and LCDB

    References
    1. "989 Schwassmannia (A922 WD)". Minor Planet Center. Retrieved 4 February 2020.
    2. Schmadel, Lutz D. (2007). "(989) Schwassmannia". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 86. doi:10.1007/978-3-540-29925-7_990. ISBN 978-3-540-00238-3.
    3. "JPL Small-Body Database Browser: 989 Schwassmannia (A922 WD)" (2019-05-11 last obs.). Jet Propulsion Laboratory. Retrieved 4 February 2020.
    4. "Asteroid 989 Schwassmannia". Small Bodies Data Ferret. Retrieved 4 February 2020.
    5. Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
    6. Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
    7. Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 4 February 2020.
    8. "LCDB Data for (989) Schwassmannia". Asteroid Lightcurve Database (LCDB). Retrieved 4 February 2020.
    9. Benishek, Vladimir; Pilcher, Frederick; Martinez, Luis (April 2014). "Rotation Period Determination for 989 Schwassmannia" (PDF). Minor Planet Bulletin. 41 (2): 133. Bibcode:2014MPBu...41..133B. ISSN 1052-8091.
    10. Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids" (PDF). Icarus. 172 (1): 179–220. Bibcode:2004Icar..172..179L. doi:10.1016/j.icarus.2004.06.006. Retrieved 4 February 2020.
    11. "Asteroid 989 Schwassmannia – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 4 February 2020.
    12. Stephens, Robert D. (April 2014). "Asteroids Observed from CS3: 2013 October-December" (PDF). Minor Planet Bulletin. 41 (2): 92–95. Bibcode:2014MPBu...41...92S. ISSN 1052-8091.
    13. Behrend, Raoul. "Asteroids and comets rotation curves – (989) Schwassmannia". Geneva Observatory. Retrieved 4 February 2020.
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