2015 SO2

2015 SO₂

Discovery
Discovered by	Črni Vrh Observatory
Discovery date	September 21, 2015
Designations
Designation	2015 SO2
Minor planet category	Aten asteroid, Earth crosser
Orbital characteristics
Epoch June 27, 2015 (JD 2457200.5)
Uncertainty parameter 5
Observation arc	9 days
Aphelion	1.10845 AU
Perihelion	0.89312 AU
Semi-major axis	1.00079 AU
Eccentricity	0.10758
Orbital period (sidereal)	1.00120 y (365.69 d)
Mean anomaly	174.47°
Inclination	9.198°
Longitude of ascending node	183.029°
Argument of perihelion	289.28°
Earth MOID	0.0206 AU
Physical characteristics
Dimensions	50–111 m[a]
Absolute magnitude (H)	23.9

2015 SO₂ (also written 2015 SO2) is an Aten asteroid that is a temporary horseshoe companion to the Earth, the ninth known Earth horseshoe librator. Prior to its most recent close encounter with our planet (2015 September 30) it was an Apollo asteroid.

Discovery

2015 SO₂ was discovered on 2015 September 21 by B. Mikuž observing with the 0.6-m f/3.3 Cichocki telescope at the Črni Vrh Observatory in Slovenia. As of 30 November 2015, it has been observed 84 times with an observation arc of 9 days.

Orbit and orbital evolution

2015 SO₂ is currently an Aten asteroid (Earth-crossing but with a period less than a year). Its semi-major axis (currently 0.999115 AU) is similar to that of Earth (0.99957 AU), but it has a relatively low eccentricity (0.108105) and moderate orbital inclination (9.181°). Gravitational interaction with Earth causes its orbit to change so that its average period is one year. It alternates between being an Aten asteroid and being an Apollo asteroid, changing dynamical status every 113 years approximately. As of 30 November 2015, this object is the 14th known Earth co-orbital and the 9th known object following a horseshoe path with respect to our planet. Its orbital evolution characterized by alternating horseshoe and quasi-satellite episodes.

Physical properties

With an absolute magnitude of 23.9 mag, it has a diameter in the range 50–111 meters (for an assumed albedo range of 0.04–0.20, respectively).

See also

• 54509 YORP
• (419624) 2010 SO16
• 3753 Cruithne

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.
• From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO₂ de la Fuente Marcos, C., de la Fuente Marcos, R. 2016, Astrophysics and Space Science, in press.

External links

• Discovery MPEC
• 2015 SO₂ data at MPC
• Crni Vrh Observatory News
• Discovery image
• The 60-cm Cichocki Sky Survey Telescope