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161989 Cacus

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161989 Cacus
Discovery^[1]^[2]
Shape model of Cacus from its lightcurve
Discovered by	H.-E. Schuster
Discovery site	La Silla Obs.
Discovery date	8 February 1978
Designations
MPC designation	(161989) Cacus
Named after	Cacus (Roman mythology)^[2]
Alternative designations	1978 CA
Minor planet category	Apollo · NEO · PHA^[1]
Orbital characteristics^[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	38.59 yr (14,096 days)
Aphelion	1.3634 AU
Perihelion	0.8828 AU
Semi-major axis	1.1231 AU
Eccentricity	0.2140
Orbital period (sidereal)	1.19 yr (435 days)
Mean anomaly	345.40°
Mean motion	0° 49^m 41.16^s / day
Inclination	26.060°
Longitude of ascending node	161.24°
Argument of perihelion	102.16°
Earth MOID	0.0152 AU · 5.9 LD
Physical characteristics
Mean diameter	0.64±0.02 km^[3] 1.126±0.073km^[4] 1.86km^[5] 1.9km^[6]
Synodic rotation period	3.7538±0.0019 h^[6] 3.756h^[7] 3.761h^[5] 3.77±0.11h^[8]
Geometric albedo	0.09^[6] 0.119 (derived)^[6] 0.199±0.052^[4] 0.46±0.09^[3]
Spectral type	Tholen = S^[1]^[6] · Q^[9] B–V = 0.910^[1] U–B = 0.484^[1]
Absolute magnitude (H)	16.58^[6]^[7] · 17.1^[4] · 17.2^[1] · 17.32^[5] · 17.43^[3]

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 SchusteratESO's La Silla Observatory in northern Chile.^[2] Its orbit is confined between Venus and Mars.

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)
1941-09-02	2418754 km	± 6 km
2022-09-01	8607710 km	± 21 km^[11]

References

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^ ^a ^b ^c ^d ^e ^f ^g ^h "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.

^ ^a ^b ^c ^d "161989 Cacus (1978 CA)". Minor Planet Center. Retrieved 13 January 2018.

^ ^a ^b ^c 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.

^ ^a ^b ^c 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. S2CID 35447010.

^ ^a ^b ^c 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.

^ ^a ^b ^c ^d ^e ^f "LCDB Data for (161989) Cacus". Asteroid Lightcurve Database (LCDB). Retrieved 13 January 2018.

^ ^a ^b 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.

^ 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.

^ 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.

^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 13 January 2018.

^ "Horizons Batch for 2022-Sep-01 06:54 UT". JPL Horizons. Archived from the original on 17 January 2022. Retrieved 17 January 2022.