| Discovery | |
|---|---|
| Discovered by | Črni Vrh Obs. |
| Discovery date | 21 September 2015 |
| Designations | |
| 2015 SO2 | |
| Orbital characteristics [2] [3] [4] | |
| Epoch 31 July 2016 (JD 2457600.5) | |
| Uncertainty parameter 1 | |
| Observation arc | 342 days |
| Aphelion | 1.10688036 AU (165.586945 Gm) |
| Perihelion | 0.890962 AU (133.2860 Gm) |
| 0.99892124 AU (149.436491 Gm) | |
| Eccentricity | 0.108076 |
| 1.00 yr (364.66602 d) | |
| 208.3767° | |
| 0° 59m 13.937s / day | |
| Inclination | 9.1750° |
| 182.9293° | |
| 290.0678° | |
| Earth MOID | 0.0191611 AU (2.86646 Gm) |
| Physical characteristics | |
| 50–111 m [a] [5] | |
| 23.9 [2] | |
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. [6] Prior to its most recent close encounter with our planet (2015 September 30) it was an Apollo asteroid.
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. [7] [8] As of 30 November 2015, it has been observed 84 times with an observation arc of 9 days. [2]
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. [6]
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). [5]
2003 YN107 is a tiny asteroid, classified as a near-Earth object of the Aten group moving in a 1:1 mean-motion resonance with Earth. Because of that, it is in a co-orbital configuration relative to Earth.
A quasi-satellite is an object in a specific type of co-orbital configuration with a planet where the object stays close to that planet over many orbital periods.
524522 Zoozve (provisional designation 2002 VE68) is a sub-kilometer sized asteroid and temporary quasi-satellite of Venus. Discovered in 2002, it was the first such object to be discovered around a major planet in the Solar System. It has nearly the same orbital period around the Sun that Venus does. In a frame of reference rotating with Venus, it appears to travel around it during one Venerean year, but it orbits the Sun, not Venus.
(322756) 2001 CK32 is a sub-kilometer asteroid and near-Earth object of the Aten group. It is also a transient Venus co-orbital, and a Mercury grazer as well as an Earth crosser. It was once designated as a potentially hazardous asteroid.
2012 XE133 is an asteroid, classified as near-Earth object of the Aten group that is a temporary co-orbital of Venus.
2013 BS45 (also written 2013 BS45) is a horseshoe companion to the Earth like 3753 Cruithne. Like Cruithne, it does not orbit the Earth in the normal sense and at times it is on the other side of the Sun, yet it still periodically comes nearer to the Earth in sort of halo orbit before again drifting away. While not a traditional natural satellite, it does not quite have normal heliocentric orbit either and these are sometimes called quasi-satellties or horseshoe orbits.
2006 JY26 is a near-Earth object that is also horseshoe companion to the Earth like 3753 Cruithne.
2012 FC71, also written 2012 FC71, is a small asteroid trapped in a Kozai resonance with the Earth.
2013 ND15 (also written 2013 ND15) is an asteroid that is a temporary trojan of Venus, the first known Venus trojan.
2014 OL339 (also written 2014 OL339) is an Aten asteroid that is a temporary quasi-satellite of Earth, the fourth known Earth quasi-satellite.
2013 LX28, is an asteroid, classified as near-Earth object of the Apollo group that is a temporary quasi-satellite of the Earth, the third known Earth quasi-satellite.
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. 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 YQ1 (also written 2015 YQ1) is an Apollo asteroid that is a temporary horseshoe companion to the Earth, the twelfth known Earth horseshoe librator. It experienced a close encounter with the Earth on 2015 December 22 at 0.0037 AU.
2015 YA is a sub-kilometer asteroid, classified as near-Earth object of the Aten group, that is a temporary horseshoe companion to the Earth. It is the 11th known Earth horseshoe librator. Prior to a close encounter with the Earth on 15 December 2015, 2015 YA was an Apollo asteroid.
2017 DR109, is a micro-asteroid, classified as near-Earth object of the Apollo group and Aten group, respectively. It is currently trapped in a 1:1 mean motion resonance with the Earth of the horseshoe type. The object was first observed on 27 February 2017, by astronomers of the Catalina Sky Survey conducted at Mount Lemmon Observatory, Arizona, United States.
A temporary satellite is an object which has been captured by the gravitational field of a planet and thus has become the planet's natural satellite, but, unlike irregular moons of the larger outer planets of the Solar System, will eventually either leave its orbit around the planet or collide with the planet. The only observed examples are 2006 RH120, a temporary satellite of Earth for twelve months from July 2006 to July 2007, 2020 CD3 and 2022 NX1. Some defunct space probes or rockets have also been observed on temporary satellite orbits.
2020 VT1 is a small asteroid, classified as a near-Earth object of the Amor group, that is a temporary horseshoe companion to Mars.
2020 PN1 is a sub-kilometer asteroid, classified as a near-Earth object of the Aten group, that is a temporary horseshoe companion to the Earth. There are dozens of known Earth horseshoe librators, some of which switch periodically between the quasi-satellite and the horseshoe co-orbital states.
2020 PP1 is a sub-kilometer asteroid, classified as a near-Earth object of the Apollo group, that is a temporary quasi-satellite of the Earth. There are over a dozen known Earth quasi-satellites, some of which switch periodically between the quasi-satellite and horseshoe co-orbital states.
2009 SH2 is a sub-kilometer near-Earth asteroid of the Aten group, discovered by the Siding Spring Survey at Siding Spring Observatory, Australia on 18 September 2009. It is in a co-orbital configuration with Earth, a type of 1:1 orbital resonance where the asteroid appears to librate around Earth's path in a horseshoe orbit when viewed in a corotating reference frame with Earth. The co-orbital state of 2009 SH2 is only temporary as it has entered it about 30 years ago and will leave it in about 100 years into the future.
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