2006 RH120
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Discovery[2]
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| Discovered by | Catalina Sky Survey (703) |
| Discovery date | 14 September 2006 |
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Designations
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| MPC designation | 2006 RH120 |
| Minor planet category |
Apollo NEO[1] |
| Epoch January 4, 2010 (2455200.5) | |
| Aphelion | 1.058 AU (Q) |
| Perihelion | 1.007 AU (q) |
| Semi-major axis | 1.033 AU (a) |
| Eccentricity | 0.0244 |
| Orbital period | 1.05 yr |
| Mean anomaly | 2.913° (M) |
| Inclination | 0.5955° |
| Longitude of ascending node | 51.12° |
| Argument of perihelion | 10.10° |
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Physical characteristics
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| Dimensions | ~3–6 metres[3] |
| Rotation period | 2.75 minutes[3] |
| Albedo | 0.1 ? |
| Absolute magnitude (H) | 29.5[1] |
2006 RH120 is a tiny near-Earth asteroid[1] with a diameter of about five metres,[3] which ordinarily orbits the Sun but makes close approaches to the Earth–Moon system every twenty years or so.[4] Occasionally the object temporarily enters Earth orbit through temporary satellite capture (TSC). During a temporary satellite capture, the meteoroid may be Earth's only other natural satellite besides the Moon. However, Alan 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".[4][5] It most recently was in Earth orbit from September 2006 to June 2007. Until given a minor planet designation on 18 February 18 2008,[2] the object was known as 6R10DB9, an internal identification number assigned by the Catalina Sky Survey.[3]
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[6] – suggested it might have been an artificial object. A precedent for this exists in J002E3, currently thought to be the third stage Saturn S-IVB booster from Apollo 12, in an almost identical orbit.[7]
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[edit] History
2006 RH120 was discovered on 14 September 2006 by the 27-inch (690 mm) Schmidt camera of the Catalina Sky Survey in Arizona.[8] "6R10DB9"[8] 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 September 14 to the NEOCP and subsequently removed with the explanation that it "was not a minor planet."[9] 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.
Later analysis shows the NEO is small enough that solar-radiation pressure is perturbing its motion perceptibly.[10] 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.[10] One hypothesis is that the object is a piece of lunar rock ejected by an impact.[4] On February 18, 2008, the object was given a minor planet designation.[2]
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).[3]
[edit] June 14, 2007 perigee
On June 14, 2007, 2006 RH120 made its fourth and last perigee of the most recent Earth encounter.[11] It was 0.7 lunar distances at closest, with an apparent magnitude of 18.5–19.0.
Astronomers at JPL Goldstone in California, USA made radar astrometry measurements on June 12, 14 and 17, 2007.
The object is now in solar orbit.[5] By 2017, this object will likely be 2 AU from the Earth on the other side of the Sun.[12] 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.[3] The next predicted near-Earth encounter is in 2028.[3]
[edit] See also
- 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
[edit] References and footnotes
- ^ a b c d e "JPL Small-Body Database Browser: (2006 RH120)". 2007-06-15 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2006RH120. Retrieved 2010-02-26.
- ^ a b c Williams, Gareth V (2008-02-18). "MPEC 2008-D12 : 2006 RH120". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. http://www.cfa.harvard.edu/mpec/K08/K08D12.html. Retrieved 2010-02-26.
- ^ a b c d e f g Great Shefford Observatory. "2006 RH120 ( = 6R10DB9) – A second moon for the Earth?". http://www.birtwhistle.org/Gallery6R10DB9.htm. Retrieved April 16, 2008.
- ^ a b c Bill Gray. "Pseudo-MPEC for 6R10DB9". http://home.gwi.net/~pluto/mpecs/6r1.htm. Retrieved August 16, 2007.
- ^ a b Roger W. Sinnott (2007-04-17). "Earth's "Other Moon"". Sky & Telescope. http://www.skyandtelescope.com/news/7067527.html. Retrieved 2010-02-25.
- ^ Spectrum measured by Carl Hergenrother and Rob Whitely of the University of Arizona.
- ^ Yeomans, Don (April 2010). "Is Another Moon Possible?". Astronomy.
- ^ a b "Distant Artificial Satellites Observation (DASO) Circular No. 68, 2006 Sept. 17, 16:59 UT". http://cfa-www.harvard.edu/~gwilliams/DASO/000000/DASO_000068.txt. Retrieved 2007-06-26.
- ^ "Major News About Minor Objects, April 18, 2007". http://www.hohmanntransfer.com/news/0704.htm#news. Retrieved 2007-06-27.
- ^ a b Dr. Lance A. M. Benner (2007-06-20). "6R10DB9 Planning". JPL/NASA Asteroid Radar Research. http://echo.jpl.nasa.gov/asteroids/6R10DB9/6R10DB9_planning.html. Retrieved 2010-02-27.
- ^ "JPL Close-Approach Data: (2006 RH120)". 2007-06-15 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2006RH120;orb=0;cad=1#cad. Retrieved 2010-02-27.
- ^ Donald K. Yeomans and Alan B. Chamberlin. "Horizons Ephemeris". JPL Solar System Dynamics. http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2006RH120. Retrieved 2010-02-25.
[edit] External links
- 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)
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