(311999) 2007 NS2

(311999) 2007 NS₂ was discovered on 14 July 2007, by the Observatorio Astronómico de La Sagra.^{[4][5][6][7][8]} Its orbit is characterized by low eccentricity (0.054), moderate inclination (18.6°) and a semi-major axis of 1.52 AU.^[8] Upon discovery, it was classified as Mars-crosser by the Minor Planet Center. Its orbit is well determined as it is currently (March 2013) based on 87 observations with a data-arc span of 4,800 days.^[2] 2007 NS₂ has an absolute magnitude of 17.8, which gives a characteristic diameter of 870 m.^[2]

Jean Meeus suspected that (311999) 2007 NS₂ was a Mars Trojan, and this was confirmed by Reiner Stoss's analysis of two sets of observations dating from 1998 on the MPC database.^[9] It was confirmed to be a Mars Trojan numerically in 2012.^[10] Recent calculations confirm that it is a stable L₅ Mars Trojan asteroid with a libration period of 1310 years and an amplitude of 14°.^[11][12] These values as well as its short-term orbital evolution are similar to those of 5261 Eureka. Out of all known Mars Trojans, it currently has the smallest relative (to Mars) semimajor axis, 0.000059 AU.^[11]

Long-term numerical integrations show that its orbit is very stable on Gyr time-scales (1 Gyr = 1 billion years). As in the case of Eureka, calculations in both directions of time (4.5 Gyr into the past and 4.5 Gyr into the future) indicate that (311999) 2007 NS₂ may be a primordial object, perhaps a survivor of the planetesimal population that formed in the terrestrial planets region early in the history of the Solar System.^[11]

• 5261 Eureka (1990 MB)
• (101429) 1998 VF31
• (121514) 1999 UJ7
• (385250) 2001 DH47
• 2009 SE
• 2011 SC191
• 2011 SL25
• 2011 SP189
• 2011 UB256
• 2011 UN63
• 2016 CP31
• 2018 EC4
• 2018 FC4
• 2020 VT1