2009 SE

2009 SE
Discovery
Discovered by	Catalina Sky Survey
Discovery date	16 September 2009
Designations
MPC designation	2009 SE
Minor planet category	Martian L5
Orbital characteristics
	Epoch 31 May 2020 (JD 2459000.5)
	Uncertainty parameter 0
Observation arc	3133 days (8.58 yr)
\|{{{apsis}}}\|helion}}	1.623684 astronomical unit\|AU (242.8997 Gm)
\|{{{apsis}}}\|helion}}	1.425261 AU (213.2160 Gm)
Semi-major axis	1.524472 AU (228.0578 Gm)
Eccentricity	0.0650794
Orbital period	1.88 yr (687.508 d)
Mean anomaly	240.916°
Mean motion	0° 31m 25.069s /day
Inclination	20.6248°
Longitude of ascending node	6.82030°
\|{{{apsis}}}\|helion}}	354.156°
Earth MOID	0.42422 AU (63.462 Gm)
Jupiter MOID	3.5304 AU (528.14 Gm)
Physical characteristics
Mean diameter	400 m
Geometric albedo	0.5–0.05 (assumed)
Absolute magnitude (H)	19.9

Short description: Small asteroid and Mars trojan

2009 SE 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

2009 SE was first observed on 16 September 2009 by the Catalina Sky Survey (CSS).^[3] Its orbit is characterized by low eccentricity (0.065), moderate inclination (20.6°) 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 56 observations with a data-arc span of 3,133 days.^[1] 2009 SE has an absolute magnitude of 19.9 which gives a characteristic diameter of 400 m.^[1]

Mars trojan and orbital evolution

Recent calculations indicate that it is a stable L₅ Mars trojan with a libration period of 1430 yr and an amplitude of 70°.^[2] The libration amplitude is not similar to that of 5261 Eureka and related objects.^{[citation needed]}