2009 SE is a small asteroid and Mars trojan orbiting near the of Mars.Discovery, orbit and physical propertieswas first observed on 16 September 2009 by the Catalina Sky Survey. Its orbit is characterized by low eccentricity, moderate inclination and a semi-major axis of 1.52 AU. Upon discovery, it was classified as Mars-crosser by the Minor Planet Center. Its orbit is well determined as it is currently based on 60 observations with a data-arc span of 5,498 days. has an absolute magnitude of 20.13 which gives a characteristic diameter of 400 m.Mars trojan and orbital evolutionRecent calculations indicate that it is a stable Mars trojan with a libration period of 1430 yr and an amplitude of 70°. The libration amplitude is not similar to that of 5261 Eureka and related objects.