Discovery | |
---|---|
Discovered by | R. G. Matheny Mount Lemmon Srvy. |
Discovery site | Mount Lemmon Obs. |
Discovery date | 9 December 2015 |
Designations | |
Designation | 2015 XX169 |
Orbital characteristics [2] | |
Epoch 16 February 2017 (JD 2457800.5) | |
Uncertainty parameter 1 | |
Observation arc | 363 days |
Aphelion | 1.18545 AU |
Perihelion | 0.81648 AU |
1.00097 AU | |
Eccentricity | 0.18431 |
1.00149 y (365.79 d) | |
345.528° | |
Inclination | 7.640° |
256.630° | |
283.587° | |
Earth MOID | 0.0154 AU |
Physical characteristics | |
Dimensions | 9–22 m [lower-alpha 1] [3] [4] |
27.4 [2] | |
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 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]
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]
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).
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