# 2009 SH2

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Near-Earth asteroid

2009 SH2 Discovery[1][2] Discovered by Siding Spring Survey Discovery site Siding Spring Obs. Discovery date 18 September 2009 Designations Minor planet category Earth co-orbital[3] · NEO Aten[4] Orbital characteristics[4] Epoch 21 November 2025 (JD 2461000.5) Uncertainty parameter 4 Observation arc 14 days Aphelion 1.085 AU Perihelion 0.8978 AU Semi-major axis 0.991 AU Eccentricity 0.09423 Orbital period (sidereal) 0.99 yr (360.47 d) Mean anomaly 30.7234° Mean motion 0° 59m 55.274s / day Inclination 6.810° Longitude of ascending node 6.657° Time of perihelion 21 October 2025 05:40 UT Argument of perihelion 101.752° Earth MOID 0.0002 AU (30,000 km) Physical characteristics Mean diameter 30–60 m (assumed albedo 0.05–0.25)[5] Synodic rotation period 1.26 h[4] Apparent magnitude 18.8 (at discovery)[1] Absolute magnitude (H) 24.9[4][2]

**2009 SH2** is a sub-kilometer [near-Earth asteroid](/source/Near-Earth_asteroid) of the [Aten group](/source/Aten_asteroid), discovered by the [Siding Spring Survey](/source/Siding_Spring_Survey) at [Siding Spring Observatory](/source/Siding_Spring_Observatory), [Australia](/source/Australia) on 18 September 2009. It is in a [co-orbital configuration](/source/Co-orbital_configuration) with Earth, a type of 1:1 [orbital resonance](/source/Orbital_resonance) where the asteroid appears to [librate](/source/Libration) around Earth's path in a [horseshoe orbit](/source/Horseshoe_orbit) when viewed in a [corotating reference frame](/source/Rotating_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.[3]

## Discovery

2009 SH2 was discovered by the [Siding Spring Survey](/source/Siding_Spring_Survey) at [Siding Spring Observatory](/source/Siding_Spring_Observatory), [Coonabarabran, New South Wales](/source/Coonabarabran%2C_New_South_Wales), [Australia](/source/Australia) on 18 September 2009. It was first observed in the [constellation](/source/Constellation) [Fornax](/source/Fornax) at an [apparent magnitude](/source/Apparent_magnitude) of 18.8.[1] The asteroid was moving at an on-sky rate around 2.5 [arcseconds](/source/Arcseconds) per minute, from a distance of 0.030 AU (4.5 million km; 2.8 million mi) from Earth.[6] Follow-up observations of the asteroid were carried out by the Rio Cuarto Observatory ([I20](/source/List_of_observatory_codes#I20)) on the following day. The asteroid was then confirmed by the [Minor Planet Center](/source/Minor_Planet_Center) and announced as 2009 SH2 on 19 September 2009.[1]

## Orbit

Orbit diagram of 2009 SH2 and the inner planets

2009 SH2 orbits the Sun at an average distance of 0.99 [AU](/source/Astronomical_unit) once every 360 days, or approximately 0.99 years. Its orbit has an [eccentricity](/source/Orbital_eccentricity) of 0.09 and an [inclination](/source/Orbital_inclination) of 7[°](/source/Degree_(angle)) with respect to the [ecliptic](/source/Ecliptic) plane. Over the course of its orbit, its distance from the Sun ranges from 0.90 AU at [perihelion](/source/Perihelion) to 1.08 AU at [aphelion](/source/Aphelion), crossing the orbit of [Earth](/source/Earth). Since its orbit crosses that of Earth's while having a [semi-major axis](/source/Semi-major_axis) less than 1 AU, 2009 SH2 is classified as an [Aten asteroid](/source/Aten_asteroid). Its nominal orbit has a small [minimum orbit intersection distance](/source/Minimum_orbit_intersection_distance) approximately 0.0006 AU (90,000 km; 56,000 mi) from Earth's orbital path and periodically makes close approaches to Earth.[4]

In 2013, astronomers Carlos and Raúl de la Fuente Marcos identified 2009 SH2 to be in a [co-orbital configuration](/source/Co-orbital_configuration) with Earth, a type of 1:1 [orbital resonance](/source/Orbital_resonance) where the asteroid appears to librate around Earth's path in a [horseshoe orbit](/source/Horseshoe_orbit) when viewed in a [corotating reference frame](/source/Rotating_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.[3]

## Physical characteristics

Based on a magnitude-to-diameter conversion and a measured [absolute magnitude](/source/Absolute_magnitude) of 24.9, 2009 SH2 measures between 30 and 60 meters in diameter for an assumed [geometric albedo](/source/Geometric_albedo) of 0.25 and 0.05, respectively.[2][5] A rotation period of 1.26 h has been tentatively measured from its [lightcurve](/source/Lightcurve).[4]

## See also

- [Arjuna asteroid](/source/Arjuna_asteroid)

- [2003 YN107](/source/2003_YN107)

- [2006 JY26](/source/2006_JY26)

- [2012 FC71](/source/2012_FC71)

- [2013 BS45](/source/2013_BS45)

## References

1. ^ [***a***](#cite_ref-MPEC-2009-S51_1-0) [***b***](#cite_ref-MPEC-2009-S51_1-1) [***c***](#cite_ref-MPEC-2009-S51_1-2) [***d***](#cite_ref-MPEC-2009-S51_1-3) ["MPEC 2009-S51 : 2009 SH2"](https://minorplanetcenter.net/mpec/K09/K09S51.html). *Minor Planet Electronic Circular*. [Minor Planet Center](/source/Minor_Planet_Center). 19 September 2009. Retrieved 12 February 2021.

1. ^ [***a***](#cite_ref-MPC-object_2-0) [***b***](#cite_ref-MPC-object_2-1) [***c***](#cite_ref-MPC-object_2-2) ["2009 SH2"](http://www.minorplanetcenter.net/db_search/show_object?object_id=2009+SH2). *Minor Planet Center*. International Astronomical Union. Retrieved 12 February 2021.

1. ^ [***a***](#cite_ref-Marcos2013_3-0) [***b***](#cite_ref-Marcos2013_3-1) [***c***](#cite_ref-Marcos2013_3-2) de la Fuente Marcos, C.; de la Fuente Marcos, R. (September 2013). ["A resonant family of dynamically cold small bodies in the near-Earth asteroid belt"](https://doi.org/10.1093%2Fmnrasl%2Fslt062). *Monthly Notices of the Royal Astronomical Society: Letters*. **434** (1): L1–L5. [arXiv](/source/ArXiv_(identifier)):[1305.2825](https://arxiv.org/abs/1305.2825). [Bibcode](/source/Bibcode_(identifier)):[2013MNRAS.434L...1D](https://ui.adsabs.harvard.edu/abs/2013MNRAS.434L...1D). [doi](/source/Doi_(identifier)):[10.1093/mnrasl/slt062](https://doi.org/10.1093%2Fmnrasl%2Fslt062).

1. ^ [***a***](#cite_ref-jpldata_4-0) [***b***](#cite_ref-jpldata_4-1) [***c***](#cite_ref-jpldata_4-2) [***d***](#cite_ref-jpldata_4-3) [***e***](#cite_ref-jpldata_4-4) [***f***](#cite_ref-jpldata_4-5) ["JPL Small-Body Database Browser: 2009 SH2"](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3467258) (2009-10-02 last obs.). [Jet Propulsion Laboratory](/source/Jet_Propulsion_Laboratory). Retrieved 12 February 2021.

1. ^ [***a***](#cite_ref-sizemagnitude_5-0) [***b***](#cite_ref-sizemagnitude_5-1) Bruton, Dan. ["Conversion of Absolute Magnitude to Diameter for Minor Planets"](https://web.archive.org/web/20110723191750/http://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html). *Department of Physics, Engineering, and Astronomy*. Stephen F. Austin State University. Archived from [the original](http://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html) on 23 July 2011. Retrieved 12 February 2021.

1. **[^](#cite_ref-NEODyS-Eph-Dis_6-0)** ["2009SH2 Ephemerides"](https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=2009SH2&oc=E12&y0=2009&m0=9&d0=18&h0=18&mi0=0&y1=2009&m1=9&d1=18&h1=19&mi1=0&ti=10&tiu=minutes). *Near Earth Objects – Dynamic Site* (Ephemerides at discovery (obs. code E12)). Department of Mathematics, University of Pisa, Italy. Retrieved 12 February 2021.

## External links

- [2009 SH2](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.0) at *NeoDyS-2, Near Earth Objects—Dynamic Site* - [Ephemerides](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.3.0) **·** [Observation prediction](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.4.0) **·** [Orbital info](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.1) **·** [MOID](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.5) **·** [Proper elements](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.6) **·** [Observational info](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.7.0) **·** [Close approaches](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.8) **·** [Physical info](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.9) **·** [Orbit animation](https://newton.spacedys.com/neodys/index.php?n=2009sh2&pc=1.1.A)

- [2009 SH2](https://neo.ssa.esa.int/search-for-asteroids?sum=1&des=2009SH2) at *ESA–[space situational awareness](/source/Space_Situational_Awareness_Programme)* - [Ephemerides](https://neo.ssa.esa.int/search-for-asteroids?des=2009SH2&tab=eph) **·** [Observations](https://neo.ssa.esa.int/search-for-asteroids?des=2009SH2&tab=obs) **·** [Orbit](https://neo.ssa.esa.int/search-for-asteroids?des=2009SH2&tab=orbprop) **·** [Physical properties](https://neo.ssa.esa.int/search-for-asteroids?des=2009SH2&tab=physprops) **·** [Summary](https://neo.ssa.esa.int/search-for-asteroids?des=2009SH2&tab=summary)

- [2009 SH2](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3467258) at the *[JPL Small-Body Database](/source/JPL_Small-Body_Database)* - [Close approach](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3467258&view=C) **·** [Discovery](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3467258&view=D) **·** [Ephemeris](https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=3467258) **·** [Orbit viewer](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3467258&view=V) **·** [Orbit parameters](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3467258&view=O) **·** [Physical parameters](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3467258&view=P)

v t e Small Solar System bodies Minor planets Designation Groups List Moon Meanings of names Asteroid Active Asteroid belt Family Jupiter trojan Near-Earth Amors Apollos Atens Atiras Spectral types Distant minor planet Centaur Neptune trojan Damocloid Trans-Neptunian object Detached Kuiper belt Oort cloud Scattered disc Comets Extinct Great Halley-type Hyperbolic/Parabolic Long-period Lost Near-parabolic Periodic Sungrazing Other Cosmic dust Meteoroids Space debris

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Adapted from the Wikipedia article [2009 SH2](https://en.wikipedia.org/wiki/2009_SH2) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/2009_SH2?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.