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1198 Atlantis
Discovery
Discovered by	K. Reinmuth
Discovery site	Heidelberg Obs.
Discovery date	7 September 1931
Designations
MPC designation	(1198) Atlantis
Pronunciation	/ætˈlæntɪs/
Named after	Island of Atlantis; (Greek mythology)
Alternative designations	1931 RA · 1958 RQ; 1975 TQ4 · 1975 VX6
Minor planet category	Mars-crosser
Symbol	(astrological)
Orbital characteristics
	Epoch 4 September 2017 (JD 2458000.5)
	Uncertainty parameter 0
Observation arc	85.48 yr (31,220 days)
Aphelion	3.0065 AU
Perihelion	1.4941 AU
Semi-major axis	2.2503 AU
Eccentricity	0.3360
Orbital period (sidereal)	3.38 yr (1,233 days)
Mean anomaly	168.18°
Mean motion	0° 17m 31.2s / day
Inclination	2.7234°
Longitude of ascending node	259.58°
Argument of perihelion	84.528°
Physical characteristics
Dimensions	3.92 km (calculated)
Synodic rotation period	16 h
Geometric albedo	0.20 (assumed)
Spectral type	SMASS = L · S
Absolute magnitude (H)	14.07±0.53 · 14.4

1198 Atlantis, provisional designation 1931 RA, is a rare-type asteroid and eccentric Mars-crosser from the inner regions of the asteroid belt, approximately 3.9 kilometers in diameter. It was discovered on 7 September 1931, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany.^[3] The asteroid was named after the mythological island of Atlantis.^[2]

Orbit

Atlantis orbits the Sun at a distance of 1.5–3.0 AU once every 3 years and 5 months (1,233 days). Its orbit has an eccentricity of 0.34 and an inclination of 3° with respect to the ecliptic.^[1] The asteroids's observation arc begins at Heidelberg one week after its official discovery observation.^[3]

Physical characteristics

In the SMASS classification, Atlantis is a rare L-type asteroid, that belong to the larger complex of stony asteroids.^[1]

Rotation period

In August 2012, a rotational lightcurve of Atlantis was obtained from photometric observations by Italian astronomer Albino Carbognani at the OAVdA Observatory (B04) in Italy. Lightcurve analysis gave a rotation period of at least 16 hours with a brightness variation of 0.20 magnitude (U=2).^[5]

Diameter and albedo

Atlantis has not been observed by any space-based survey, such as the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, or the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 3.92 kilometers based on an absolute magnitude of 14.4.^[4]

Naming

This minor planet was named after the fictional island of Atlantis from Greek mythology, mentioned in some of Plato's works around 360 BC. The greedy and morally bankrupt civilization of Atlantis was punished by the gods with fire and earthquakes that caused the island to sink into the sea. The naming was suggested by astronomer Gustav Stracke, after whom the asteroids (1227) through (1234) were indirectly named by the discoverer.^[2]