|Discovered by||Catalina Sky Survey (703)|
|Discovery date||14 September 2006|
|MPC designation||2006 RH120|
|Minor planet category||Apollo NEO|
|Epoch 4 January 2010 (2455200.5)|
|Aphelion||1.058 AU (Q)|
|Perihelion||1.007 AU (q)|
|Semi-major axis||1.033 AU (a)|
|Orbital period||1.05 yr|
|Mean anomaly||2.913° (M)|
|Longitude of ascending node||51.12°|
|Argument of perihelion||10.10°|
|Rotation period||2.75 minutes|
|Absolute magnitude (H)||29.5|
2006 RH120 is a tiny near-Earth asteroid with a diameter of about 5 meters (5.5 yards), which ordinarily orbits the Sun but makes close approaches to the Earth–Moon system every twenty years or so, when it can temporarily enter Earth orbit through temporary satellite capture (TSC). It most recently was in Earth orbit from September 2006 to June 2007.
2006 RH120 was discovered on 14 September 2006 by the 27-inch (690 mm) Schmidt camera of the Catalina Sky Survey in Arizona. "6R10DB9" was the Catalina Sky Survey's own discovery designation for this object, which usually would only be used on the MPC's NEO Confirmation Page (NEOCP) until an IAU designation was applied, if the object was classified as a minor object. It was added on 14 September to the NEOCP and subsequently removed with the explanation that it "was not a minor planet." Preliminary orbital calculations indicated it was captured by Earth's gravity from solar orbit of a period of about 11 months, which is similar to that of many spent rocket boosters dating to the Apollo program of the 1960s and early 1970s.
Some controversy existed regarding the origin of the object. Upon discovery, it was not given a formal name since its size, orbit and spectrum – consistent with the white titanium oxide paint used on Saturn V rockets – suggested it might have been an artificial object. Precedents for this exist: J002E3 is currently thought to be the third stage Saturn S-IVB booster from Apollo 12 and was in an almost identical orbit, and 6Q0B44E which had been discovered a month earlier and was also thought to be artificial. Its status as satellite was also debated, with A. W. Harris of the Space Science Institute comments, "Claiming some bit of fluff in a temporary looping orbit to be a ‘satellite,’ with all the baggage that term carries, is mere hype".
Analysis has shown that solar-radiation pressure is perturbing its motion perceptibly. However, Paul Chodas in JPL's Solar System Dynamics Group suspects that the perturbations are consistent with expectations for a rocky object but not with old flight hardware. One hypothesis is that the object is a piece of lunar rock ejected by an impact. On 18 February 2008, the object was given a minor planet designation.
The object made four Earth orbits before being ejected after the June 2007 perigee. At that perigee, it dipped inside the Moon's orbit to a distance of 276,845 kilometres (172,024 mi).
14 June 2007 perigee
The object is now in solar orbit. By 2017, this object will likely be 2 AU from the Earth on the other side of the Sun. Systematic residuals in the positions of the object probably indicate that the model used to determine solar radiation pressure may be too simple to adequately describe its motion over a long period of time. The next predicted near-Earth encounter is in 2028.
- 6Q0B44E – Another small Earth satellite, probably artificial
- 3753 Cruithne – horseshoe companion of the Earth
- 2002 AA29 – horseshoe companion of the Earth
- 2010 SO16 – horseshoe companion of the Earth
- Natural satellite
- Other moons of Earth
References and footnotes
- "JPL Small-Body Database Browser: (2006 RH120)". 15 June 2007 last obs. Retrieved 26 February 2010.
- Williams, Gareth V (18 February 2008). "MPEC 2008-D12 : 2006 RH120". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Archived from the original on 9 April 2010. Retrieved 26 February 2010.
- Great Shefford Observatory. "2006 RH120 ( = 6R10DB9) – A second moon for the Earth?". Archived from the original on 9 May 2008. Retrieved 16 April 2008.
- Bill Gray. "Pseudo-MPEC for 6R10DB9". Archived from the original on 27 September 2007. Retrieved 16 August 2007.
- I. Klotz - Mystery Mini Moons: How Many Does Earth Have? (2012) - Discovery News
- "Distant Artificial Satellites Observation (DASO) Circular No. 68, 2006 Sept. 17, 16:59 UT". Retrieved 26 June 2007.
- "Major News About Minor Objects, April 18, 2007". Retrieved 27 June 2007.
- Spectrum measured by Carl Hergenrother and Rob Whitely of the University of Arizona.
- Yeomans, Don (April 2010). "Is Another Moon Possible?". Astronomy.
- The Guardian, Spacewatch, 6 September 2006
- Roger W. Sinnott (17 April 2007). "Earth's "Other Moon"". Sky & Telescope. Retrieved 25 February 2010.
- Dr. Lance A. M. Benner (20 June 2007). "6R10DB9 Planning". JPL/NASA Asteroid Radar Research. Retrieved 27 February 2010.
- "JPL Close-Approach Data: (2006 RH120)". 15 June 2007 last obs. Retrieved 27 February 2010.
- Donald K. Yeomans and Alan B. Chamberlin. "Horizons Ephemeris". JPL Solar System Dynamics. Retrieved 25 February 2010.
- Great Shefford Observatory's 6R10DB9 images and background
- Earth's "Other Moon" on SkyandTelescope.com
- JPL Radar Astrometry Page
- Bill Gray's Pseudo-MPEC Page on 6R10DB9
- Orbital simulation from JPL (Java) / Horizons Ephemeris
- Photometry of 2006 RH120: an asteroid temporarily captured into a geocentric orbit (Astronomy & Astrophysics 2009)