2015 XX169

2015 XX169 (also written 2015 XX169) is an Apollo asteroid that is a temporary horseshoe companion to the Earth, the tenth known Earth horseshoe librator.[5] A close encounter with the Earth on 14 December 2015 caused the value of the semi-major axis of 2015 XX169 to drift slowly upwards, and the object evolved from an Aten asteroid to an Apollo asteroid about a year after this close approach.

2015 XX169
Discovery
Discovered byR. G. Matheny
Mount Lemmon Srvy.
Discovery siteMount Lemmon Obs.
Discovery date9 December 2015
Designations
Designation
2015 XX169
Orbital characteristics[2]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 1
Observation arc363 days
Aphelion1.18545 AU
Perihelion0.81648 AU
1.00097 AU
Eccentricity0.18431
1.00149 y (365.79 d)
345.528°
Inclination7.640°
256.630°
283.587°
Earth MOID0.0154 AU
Physical characteristics
Dimensions9–22 m[lower-alpha 1][3][4]
27.4[2]

    Discovery

    2015 XX169 was discovered on 9 December 2015 by R. G. Matheny observing with the 1.5-m reflector telescope at the Mount Lemmon Survey.[6] As of 6 December 2016, it has been observed 47 times with an observation arc of 363 days.[2]

    Orbit and orbital evolution

    2015 XX169 is currently an Apollo asteroid (Earth-crossing but with a period greater than a year). Its semi-major axis (currently 1.00096 AU) is similar to that of Earth (1.00074 AU), but it has a relatively low eccentricity (0.18431) and moderate orbital inclination (7.640°). It alternates between being an Apollo asteroid and being an Aten asteroid, changing dynamical status approximately every 130 years. 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°.[5]

    Physical properties

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

    See also

    Notes
    1. This is assuming an albedo of 0.20–0.04.

    References
    1. List Of Apollo Minor Planets
    2. "2015 XX169". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 3736412. Retrieved 6 December 2016.
    3. "Conversion of Absolute Magnitude to Diameter". Minor Planet Center. Retrieved 14 April 2020.
    4. Chesley, Steven R.; Chodas, Paul W.; Milani, Andrea; Valsecchi, Giovanni B.; Yeomans, Donald K. (October 2002). "Quantifying the Risk Posed by Potential Earth Impacts" (PDF). Icarus. 159 (2): 425. Bibcode:2002Icar..159..423C. doi:10.1006/icar.2002.6910. Archived from the original (PDF) on 4 November 2003. Retrieved 15 April 2020.
    5. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (1 April 2016). "A trio of horseshoes: past, present and future dynamical evolution of Earth co-orbital asteroids 2015 XX169, 2015 YA and 2015 YQ1". Astrophysics and Space Science. 361 (4): 121 (13 pages). arXiv:1603.02415. Bibcode:2016Ap&SS.361..121D. doi:10.1007/s10509-016-2711-6. S2CID 189843906.
    6. Discovery MPEC

    Further reading
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