911 Agamemnon

Shape model of Agamemnon from its lightcurve
Discovery [1]
Discovered by	K. Reinmuth
Discovery site	Heidelberg Obs.
Discovery date	19 March 1919
Designations
MPC designation	(911) Agamemnon
Pronunciation	/æɡəˈmɛmnɒn/[2]
Named after	Agamemnon [3] (Greek mythology)
Alternative designations	1919 FD · 1937 QD
Minor planet category	Jupiter trojan [1][4][5] Greek [6][7] · background [7]
Adjectives	Agamemnonian /ˌæɡəmɛmˈnoʊniən/[8]
Orbital characteristics [4]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	97.93 yr (35,770 d)
Aphelion	5.6232 AU
Perihelion	4.9300 AU
Semi-major axis	5.2766 AU
Eccentricity	0.0657
Orbital period (sidereal)	12.12 yr (4,427 d)
Mean anomaly	236.05°
Mean motion	0° 4m 52.68s / day
Inclination	21.763°
Longitude of ascending node	338.01°
Argument of perihelion	80.874°
Known satellites	1 (suspected)[9]
Jupiter MOID	0.1064 AU
TJupiter	2.8530
Physical characteristics
Dimensions	190.6 km × 143.8 km[10]
Mean diameter	131.04±1.19 km[11] 166.66±3.9 km[12] 169±3 km[9] 185.30±3.37 km[13]
Synodic rotation period	6.5819±0.0007 h[14] 6.59±0.01 h[15][16][a] 6.592±0.004 h[17]
Geometric albedo	0.037±0.001[13] 0.0444±0.002[12] 0.072±0.010[11]
Spectral type	D (Tholen)[4][5] D (S3OS2)[18] U–B = 0.215±0.021[19] B–V = 0.760±0.014[19] V–I = 0.980±0.038[5]
Absolute magnitude (H)	7.89[1][4][11][12][13] 8.27[20]

911 Agamemnon, provisional designation 1919 FD, is a large Jupiter trojan and a suspected binary asteroid from the Greek camp, approximately 168 kilometers (100 miles) in diameter. It was discovered on 19 March 1919, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany.^[1] The dark D-type asteroid is one of the largest Jupiter trojans and has a rotation period of 6.6 hours.^[5] It is named after the Greek King Agamemnon, a main character of the Iliad.^[3]

Orbit and classification

Agamemnon is a dark Jovian asteroid orbiting in the Greek camp at Jupiter's leading L₄ Lagrangian point, 60° ahead of its orbit in a 1:1 resonance (see Trojans in astronomy).^[6] It is also a non-family asteroid in the Jovian background population.^[7]

It orbits the Sun at a distance of 4.9–5.6 AU once every 12 years and 1 month (4,427 days; semi-major axis of 5.28 AU). Its orbit has an eccentricity of 0.07 and an inclination of 22° with respect to the ecliptic.^[4] The body's observation arc begins at Heidelberg in October 1927, more than 8 years after its official discovery observation.^[1]

Physical characteristics

In the Tholen classification, Agamemnon is a dark D-type asteroid.^[19] It has also been characterized as a D-type in both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2).^[19][18]

Rotation period

Photometric observations of this asteroid during 1997 were used to build a lightcurve showing a rotation period of 6.5819±0.0007 hours with a brightness variation of 0.29±0.01 magnitude. A 2009 study yielded a period of 6.592±0.004 hours, in reasonable agreement with the previous result.^[5][14]

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 Wide-field Infrared Survey Explorer, Agamemnon measures between 131.04 and 185.30 kilometers in diameter, based on a common absolute magnitude of 7.89 and a surface albedo between 0.037 and 0.072.^[11][12][13] A concurring diameter estimate of 169±3 kilometers from an occultation event (see below) has also been obtained.^[9] The Collaborative Asteroid Lightcurve Link agrees with the results obtained by IRAS, that is, an albedo of 0.0444 and a diameter of 166.66 kilometers based on an absolute magnitude of 7.89.^[5]

Shape and satellite

A 2012 occultation produced a 2D shape model of roughly 190.6 km × 143.8 km (with an irregular, skewed outline)^[10] and are suggestive of Agamemnon to have a satellite of approximately 5+5
−2 kilometers in diameter orbiting at 278±5 km from the primary's center.^[9]

Naming

This minor planet named from Greek mythology after King Agamemnon, the leader of the Greeks in the Trojan War. He is a main character of Homer's Iliad. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 88).^[3]