161989 Cacus

161989 Cacus (prov. designation: 1978 CA) is a stony asteroid, classified as near-Earth object and a potentially hazardous asteroid of the Apollo group, approximately 1 kilometer in diameter. It was discovered on 8 February 1978, by German astronomer Hans-Emil Schuster at ESO's La Silla Observatory in northern Chile.[2] Its orbit is confined between Venus and Mars.

161989 Cacus
Shape model of Cacus from its lightcurve
Discovery[1][2]
Discovered byH.-E. Schuster
Discovery siteLa Silla Obs.
Discovery date8 February 1978
Designations
(161989) Cacus
Named after
Cacus (Roman mythology)[2]
1978 CA
Apollo · NEO · PHA[1]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc38.59 yr (14,096 days)
Aphelion1.3634 AU
Perihelion0.8828 AU
1.1231 AU
Eccentricity0.2140
1.19 yr (435 days)
345.40°
0° 49m 41.16s / day
Inclination26.060°
161.24°
102.16°
Earth MOID0.0152 AU · 5.9 LD
Physical characteristics
Mean diameter
0.64±0.02 km[3]
1.126±0.073 km[4]
1.86 km[5]
1.9 km[6]
3.7538±0.0019 h[6]
3.756 h[7]
3.761 h[5]
3.77±0.11 h[8]
0.09[6]
0.119 (derived)[6]
0.199±0.052[4]
0.46±0.09[3]
Tholen = S[1][6] · Q[9]
B–V = 0.910[1]
U–B = 0.484[1]
16.58[6][7] · 17.1[4] · 17.2[1] · 17.32[5] · 17.43[3]

    This minor planet was named from Roman mythology, after Cacus, a fire-breathing monster, which was killed by Hercules.[2] The official naming citation was published by the Minor Planet Center on 24 November 2007 (M.P.C. 61270).[10]

    Close approaches[1]
    Date JPL SBDB
    nominal geocentric
    distance    		 uncertainty
    region
    (3-sigma)
    1941-09-022418754 km± 6 km
    2022-09-018607710 km± 21 km[11]

    References
    1. "JPL Small-Body Database Browser: 161989 Cacus (1978 CA)" (2016-09-12 last obs.). Jet Propulsion Laboratory. Archived from the original on 22 November 2020. Retrieved 13 January 2018.
    2. "161989 Cacus (1978 CA)". Minor Planet Center. Retrieved 13 January 2018.
    3. Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63.
    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.
    5. Degewij, J.; Lebofsky, L.; Lebofsky, M. (March 1978). "1978 CA and 1978 DA". IAU Circ. 3193 (3193): 1. Bibcode:1978IAUC.3193....1D. Retrieved 13 January 2018.
    6. "LCDB Data for (161989) Cacus". Asteroid Lightcurve Database (LCDB). Retrieved 13 January 2018.
    7. Schuster, H. E.; Surdej, A.; Surdej, J. (September 1979). "Photoelectric observations of two unusual asteroids - 1978 CA and 1978 DA". Astronomy and Astrophysics Supplement Series. 37: 483–486. Bibcode:1979A&AS...37..483S.
    8. Koehn, Bruce W.; Bowell, Edward G.; Skiff, Brian A.; Sanborn, Jason J.; McLelland, Kyle P.; Pravec, Petr; et al. (October 2014). "Lowell Observatory Near-Earth Asteroid Photometric Survey (NEAPS) - 2009 January through 2009 June". The Minor Planet Bulletin. 41 (4): 286–300. Bibcode:2014MPBu...41..286K. ISSN 1052-8091.
    9. Thomas, Cristina A.; Emery, Joshua P.; Trilling, David E.; Delbó, Marco; Hora, Joseph L.; Mueller, Michael (January 2014). "Physical characterization of Warm Spitzer-observed near-Earth objects". Icarus. 228: 217–246. arXiv:1310.2000. Bibcode:2014Icar..228..217T. doi:10.1016/j.icarus.2013.10.004.
    10. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 13 January 2018.
    11. "Horizons Batch for 2022-Sep-01 06:54 UT". JPL Horizons. Archived from the original on 17 January 2022. Retrieved 17 January 2022.
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