2011 UB256

2011 UB₂₅₆ is a small asteroid and Mars trojan orbiting near the L₅ point of Mars (60 degrees behind Mars on its orbit).^[2][3][4]

2011 UB₂₅₆

Discovery
Discovered by	Pan-STARRS
Discovery date	29 October 2011
Designations
MPC designation	2011 UB256
Minor planet category	Martian L5
Orbital characteristics[1]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc	6265 days (17.15 yr)
Aphelion	1.631894031 AU (244.1278722 Gm)
Perihelion	1.4154896 AU (211.75423 Gm)
Semi-major axis	1.523691798 AU (227.9410486 Gm)
Eccentricity	0.0710132
Orbital period (sidereal)	1.88 yr (686.980044 d)
Mean anomaly	180.60444°
Mean motion	0° 31m 26.518s /day
Inclination	24.30270°
Longitude of ascending node	58.781126°
Argument of perihelion	7.58178°
Earth MOID	0.428887 AU (64.1606 Gm)
Jupiter MOID	3.5641 AU (533.18 Gm)
Physical characteristics
Mean diameter	300 m
Geometric albedo	0.5-0.05 (assumed)
Absolute magnitude (H)	19.9

Discovery, orbit and physical properties

2011 UB₂₅₆ was first observed on 29 October 2011 by the Pan-STARRS 1 telescope system at Haleakala; the Apache Point-Sloan Digital Sky Survey had imaged this object on 31 March 2003 without identifying it as an asteroid.^[5] Its orbit is characterized by low eccentricity (0.071), moderate inclination (24.3°) and a semi-major axis of 1.52 AU.^[5] 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 64 observations with a data-arc span of 6265 days.^[1] 2011 UB₂₅₆ has an absolute magnitude of 19.9 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.^[2] It may not be a member of the so-called Eureka family.

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

1. "JPL Small-Body Database Browser: (2011 UB256)". Jet Propulsion Laboratory. Retrieved 12 January 2021.
2. Christou, Apostolos A.; Borisov, Galin; Dell'Oro, Aldo; Jacobson, Seth A.; Cellino, Alberto; Unda-Sanzana, Eduardo (January 2020). "Population control of Mars Trojans by the Yarkovsky & YORP effects". Icarus. 335 (1): 113370 (34 pages). arXiv:1907.12858. Bibcode:2020Icar..33513370C. doi:10.1016/j.icarus.2019.07.004. S2CID 198985887.
3. Christou, Apostolos A.; Borisov, Galin; Dell'Oro, Aldo; Cellino, Alberto; Devogèle, Maxime (January 2021). "Composition and origin of L₅ Trojan asteroids of Mars: Insights from spectroscopy". Icarus. 354 (1): 113994 (22 pages). arXiv:2010.10947. Bibcode:2021Icar..35413994C. doi:10.1016/j.icarus.2020.113994. S2CID 224814529.
4. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (March 2021). "Using Mars co-orbitals to estimate the importance of rotation-induced YORP break-up events in Earth co-orbital space". Monthly Notices of the Royal Astronomical Society. 501 (4): 6007–6025. arXiv:2101.02563. Bibcode:2021MNRAS.501.6007D. doi:10.1093/mnras/stab062.
5. MPC data on 2011 SP189

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

• 2011 UB₂₅₆ data at MPC.
• 2011 UB256 at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 2011 UB256 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical properties · Summary
• 2011 UB256 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters