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2015 SO₂ (astronomical naming convention: 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 21 September 2015 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 is characterized by alternating horseshoe and quasi-satellite episodes.

Physical properties

With an absolute magnitude of 23.9, it has a diameter in the range of 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

1. List Of Aten Minor Planets
2. ^ "2015 SO2". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 3728565. Retrieved 4 April 2016.
3. AstDys-2 on 2015 SO2 Retrieved 2015-11-28
4. NEODyS-2 on 2015 SO2 Retrieved 2015-11-28
5. ^ "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 16 February 2018.
6. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (2016). "From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2". Astrophysics and Space Science. 361 (1): 16. arXiv:1511.08360. Bibcode:2016Ap&SS.361...16D. doi:10.1007/s10509-015-2597-8. S2CID 189842725.
7. Discovery MPEC
8. News release

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, Vol. 361, Issue 1, article 16 (10 pp).

External links

• Discovery MPEC
• 2015 SO₂ data at MPC
• Crni Vrh Observatory News
• Discovery image
• The 60-cm Cichocki Sky Survey Telescope
• 2015 SO2 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
• 2015 SO2 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical properties · Summary
• 2015 SO2 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

v t e 2015 in space
« 2014 2016 »
Space probe launches	Space probes SMAP (weather satellite; Jan 2015) LISA Pathfinder (technology demonstration; Dec 2015) Space observatories DSCOVR (weather satellite; Feb 2015) Astrosat (space telescope; Sep 2015)
Impact events	2015 Kerala meteoroid 2015 Thailand bolide WT1190F impact
Selected NEOs	Asteroid close approaches 2015 BP513 (357439) 2004 BL86 2015 AZ43 (523775) 2014 YB35 1566 Icarus 2015 HM10 2015 TC25 2015 TB145 2007 VE191 (33342) 1998 WT24 (85989) 1999 JD6 2015 SO2
Exoplanets	Aldebaran b evaporation of Gliese 436 b Gliese 1132 b HD 155233 b HD 164595 b HD 219134 b c d f g? h? HIP 11915 b K2-3d K2-18b K2-22b K2-24b K2-24c KELT-4Ab Kepler-438b Kepler-440b Kepler-442b Kepler-444 b c d e f Kepler-451b Kepler-452b Kepler-453b KOI-4878.01 LkCa 15 b spectrum of 51 Pegasi b WASP-121b Wolf 1061c
Discoveries	2015 BP519 US 708 EGS-zs8-1 (announced) WISE J224607.57−052635.0 1SWASP J093010.78+533859.5 ASASSN-15lh EGSY8p7 Tabby's Star 541132 Leleākūhonua VFTS 352 contact binary GW150914 (first observation of gravitational waves) GW151226
Comets	15P/Finlay C/2014 Q2 (Lovejoy) 88P/Howell C/2014 Q1 (PanSTARRS) C/2015 G2 (MASTER) C/2013 US10 (Catalina) 67P/Churyumov–Gerasimenko 10P/Tempel
Space exploration	Rosetta (orbiting comet 67P; Nov 2014 / Mar 2015) Dawn (Ceres orbit insertion; Mar 2015) MESSENGER (end of mission; Apr 2015) New Horizons (flyby of Pluto; Jul 2015) Akatsuki (Venus orbit insertion; Dec 2015)
Outer space portal Category:2014 in outer space — Category:2015 in outer space — Category:2016 in outer space

• Aten asteroids
• Minor planet object articles (unnumbered)
• Earth-crossing asteroids
• Earth co-orbital asteroids
• Astronomical objects discovered in 2015