2015 XX169

2015 XX₁₆₉

Discovery
Discovered by	Mount Lemmon Survey
Discovery date	December 9, 2015
Designations
Designation	2015 XX169
Minor planet category	Aten asteroid, Earth crosser
Orbital characteristics
Epoch January 13, 2016 (JD 2457400.5)
Uncertainty parameter 5
Observation arc	4 days
Aphelion	1.18333 AU
Perihelion	0.81614 AU
Semi-major axis	0.99974 AU
Eccentricity	0.18364
Orbital period (sidereal)	0.99962 y (365.11 d)
Mean anomaly	310.655°
Inclination	7.691°
Longitude of ascending node	256.7497°
Argument of perihelion	283.918°
Earth MOID	0.0150 AU
Physical characteristics
Dimensions	9–22 m[a]
Absolute magnitude (H)	27.4

2015 XX₁₆₉ (also written 2015 XX169) is an Aten asteroid that is a temporary horseshoe companion to the Earth, the tenth known Earth horseshoe librator. A close encounter with the Earth on 2015 December 14 caused the value of the semi-major axis of 2015 XX₁₆₉ to drift slowly upwards and the object will become an Apollo asteroid about a year after this close approach.

Discovery

2015 XX₁₆₉ was discovered on 2015 December 9 by R. G. Matheny observing with the 1.5-m reflector telescope at the Mount Lemmon Survey. As of 9 March 2016, it has been observed 37 times with an observation arc of 4 days.

Orbit and orbital evolution

2015 XX₁₆₉ is currently an Aten asteroid (Earth-crossing but with a period less than a year). Its semi-major axis (currently 0.99974 AU) is similar to that of Earth (1.00074 AU), but it has a relatively low eccentricity (0.18364) and moderate orbital inclination (7.691°). It alternates between being an Aten asteroid and being an Apollo asteroid, changing dynamical status every 130 years approximately. As of 9 March 2016, this object is the 15th known Earth co-orbital and the 10th known object following a horseshoe path with respect to our planet. Asteroid 2015 XX₁₆₉ follows an asymmetrical horseshoe path with respect to our planet; the value of its relative mean longitude oscillates about 180°, but enclosing 0°.

Physical properties

With an absolute magnitude of 27.4 mag, it has a diameter in the range 9–22 meters (for an assumed albedo range of 0.04–0.20, respectively).

See also

• 54509 YORP
• (419624) 2010 SO16
• 3753 Cruithne
• 2015 SO2
• 2015 YA
• 2015 YQ1

Notes

• ^{^} This is assuming an albedo of 0.20–0.04.

References

Further reading

• Understanding the Distribution of Near-Earth Asteroids Bottke, W. F., Jedicke, R., Morbidelli, A., Petit, J.-M., Gladman, B. 2000, Science, Vol. 288, Issue 5474, pp. 2190–2194.
• A Numerical Survey of Transient Co-orbitals of the Terrestrial Planets Christou, A. A. 2000, Icarus, Vol. 144, Issue 1, pp. 1–20.
• Debiased Orbital and Absolute Magnitude Distribution of the Near-Earth Objects Bottke, W. F., Morbidelli, A., Jedicke, R., Petit, J.-M., Levison, H. F., Michel, P., Metcalfe, T. S. 2002, Icarus, Vol. 156, Issue 2, pp. 399–433.
• Transient co-orbital asteroids Brasser, R., Innanen, K. A., Connors, M., Veillet, C., Wiegert, P., Mikkola, S., Chodas, P. W. 2004, Icarus, Vol. 171, Issue 1, pp. 102–109.
• A trio of horseshoes: past, present and future dynamical evolution of Earth co-orbital asteroids 2015 XX₁₆₉, 2015 YA and 2015 YQ₁ de la Fuente Marcos, C., de la Fuente Marcos, R. 2016, Astrophysics and Space Science, Vol. 361, Issue 4, article 121 (13 pp.)

External links

• Discovery MPEC
• 2015 XX₁₆₉ data at MPC
• ADS MPEC record
• Sciency Thoughts blog entry
• 2015 XX169 at the JPL Small-Body Database