2018 EC₄

Discovery
Discovered by	Mt. Lemmon Survey
Discovery date	10 March 2018
Designations
MPC designation	2018 EC4
Minor planet category	Martian L5
Orbital characteristics [1]
Epoch 31 May 2020 ( JD 2459000.5)
Uncertainty parameter 0
Observation arc	3131 days (8.57 yr)
Aphelion	1.61579336  AU (241.719246  Gm)
Perihelion	1.43135923 AU (214.128293 Gm)
Semi-major axis	1.52357630 AU (227.923770 Gm)
Eccentricity	0.06052671
Orbital period (sidereal)	1.88 yr (686.90193 d)
Mean anomaly	203.4934 °
Mean motion	0° 31m 26.732s /day
Inclination	21.835796°
Longitude of ascending node	47.371564°
Argument of perihelion	344.1754°
Earth  MOID	0.443437 AU (66.3372 Gm)
Jupiter  MOID	3.54199 AU (529.874 Gm)
Physical characteristics
Dimensions	300 m
Geometric albedo	0.5-0.05 (assumed)
Absolute magnitude (H)	20.1

2018 EC₄ is a small asteroid and Mars trojan orbiting near the L₅ point of Mars (60 degrees behind Mars on its orbit). ^[2]

Discovery, orbit and physical properties

2018 EC₄ was first observed on 10 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 29 October 2011. ^[3] Its orbit is characterized by low eccentricity (0.061), moderate inclination (21.8°) 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 well determined as it is currently (January 2021) based on 70 observations with a data-arc span of 3,131 days. ^[1] 2018 EC₄ has an absolute magnitude of 20.1 which gives a characteristic diameter of 300 m. ^[1]

Mars trojan and orbital evolution

Recent calculations indicate that it is a stable L₅ Mars trojan with a libration period of 1250 yr and an amplitude of 17°. ^[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.^{[ citation needed]}

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

References

Further reading

• Three new stable L5 Mars Trojans de la Fuente Marcos, C., de la Fuente Marcos, R. 2013, Monthly Notices of the Royal Astronomical Society: Letters, Vol. 432, Issue 1, pp. 31–35.
• Orbital clustering of Martian Trojans: An asteroid family in the inner solar system? Christou, A. A. 2013, Icarus, Vol. 224, Issue 1, pp. 144–153.

External links

• 2018 EC₄ data at MPC.
• 2018 EC4 at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 2018 EC4 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters