2018 FC4

2018 FC₄ is a small asteroid and Mars trojan orbiting near the L₅ point of Mars (60 degrees behind Mars on its orbit).^[2]

2018 FC₄

Discovery
Discovered by	Mt. Lemmon Survey
Discovery date	21 March 2018
Designations
MPC designation	2018 FC4
Minor planet category	Martian L5
Orbital characteristics[1]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc	790 days (2.16 yr)
Aphelion	1.5498684 AU (231.85701 Gm)
Perihelion	1.497823 AU (224.0711 Gm)
Semi-major axis	1.5238457 AU (227.96407 Gm)
Eccentricity	0.017077
Orbital period (sidereal)	1.88 yr (687.0841 d)
Mean anomaly	4.660°
Mean motion	0° 31m 26.232s /day
Inclination	22.1437°
Longitude of ascending node	187.55390°
Argument of perihelion	52.009°
Earth MOID	0.507683 AU (75.9483 Gm)
Jupiter MOID	3.41333 AU (510.627 Gm)
Physical characteristics
Dimensions	200 m
Geometric albedo	0.5-0.05 (assumed)
Absolute magnitude (H)	21.3

Discovery, orbit and physical properties

2018 FC₄ was first observed on 21 March 2018 by the Mt. Lemmon Survey, but it had already been imaged (but not identified as an asteroid) by the Pan-STARRS 1 telescope system at Haleakala on the previous night.^[3] Its orbit is characterized by very low eccentricity (0.017), moderate inclination (22.1°) and a semi-major axis of 1.52 AU.^[3] Upon discovery, it was classified as Mars-crosser by the Minor Planet Center. Its orbit is reasonably well determined as it is currently (January 2021) based on 35 observations with a data-arc span of 790 days.^[1] 2018 FC₄ has an absolute magnitude of 21.3 which gives a characteristic diameter of 200 m.^[1]

Mars trojan and orbital evolution

Recent calculations indicate that it is a stable L₅ Mars trojan with a libration period of 1300 yr and an amplitude of 20°.^[2] These values are similar to those of 5261 Eureka and related objects and it may be a member of the so-called Eureka family.

Mars trojan

L₄ (leading):

• (121514) 1999 UJ7 †

L₅ (trailing):

• 5261 Eureka (1990 MB) †
• (101429) 1998 VF31 †
• (311999) 2007 NS2 †
• (385250) 2001 DH47
• 2009 SE
• 2011 SC191
• 2011 SL25
• 2011 SP189
• 2011 UB256
• 2011 UN63
• 2016 CP31
• 2018 EC4
• 2018 FC4

See also

• 2020 VT1