2011 SP189

2011 SP₁₈₉ is a small asteroid and Mars trojan orbiting near the L₅ point of Mars (60 degrees behind Mars on its orbit).

2011 SP₁₈₉ was first observed on 29 September 2011 by the Mount Lemmon Survey. Its orbit is characterized by low eccentricity (0.040), moderate inclination (19.9°) and a semi-major axis of 1.52 AU. Upon discovery, it was classified as Mars-crosser by the Minor Planet Center. It is now classified as a Mars trojan. Its orbit is well determined as it is currently (January 2021) based on 45 observations with a data-arc span of 2390 days. 2011 SP₁₈₉ has an absolute magnitude of 20.9 which gives a characteristic diameter of 300 m.

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

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

• 2020 VT1

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.

• 2011 SP₁₈₉ data at MPC.
• 2011 SP189 at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 2011 SP189 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical properties · Summary
• 2011 SP189 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters