2006 RH120

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name= 2006 RH₁₂₀
Ephemeris is variable due to proximity and Earth's gravity. Customized ephemerides available at http://ssd.jpl.nasa.gov/horizons.cgi
discoverer=Catalina Sky Survey
discovered=14 September 2006
Eccentricity "(e)"
dimensions=~3-4 m
mass=~1.0e|3? kg
density=2 ? g/cm³
rotation=? 1.1 h
abs_magnitude=29-30
albedo=0.1 ?

2006 RH₁₂₀ is the provisional designation for a small asteroid, with a diameter estimated at two meters [cite web |url=http://echo.jpl.nasa.gov/asteroids/6R10DB9/html/6R10DB9_planning.html |title= JPL Goldstone Planning Page |accessdate=2007-06-07] which ordinarily orbits the Sun but temporarily enters Earth orbit about every 21 years. It most recently was in Earth orbit from September 2006 to June 2007. Until given a minor planet designation on February 18, 2008, the object was known as 6R10DB9, an internal identification number assigned by the Catalina Sky Survey. [cite web| url=http://www.birtwhistle.org/Gallery6R10DB9.htm| title=2006 RH120 ( = 6R10DB9) - A second moon for the Earth?| author=Great Shefford Observatory| accessdate=April 16| accessyear=2008| ]

Some controversy existed regarding the origin of the object. Upon discovery, it was not given a formal name since its size and orbit suggested it may 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.

History

2006 RH₁₂₀ was discovered on 14 September 2006 by the 27-inch Schmidt camera of the Catalina Sky Survey in Arizona. [cite web |url=http://cfa-www.harvard.edu/~gwilliams/DASO/000000/DASO_000068.txt |title=Distant Artificial Satellites Observation (DASO) Circular No. 68, 2006 Sept. 17, 16:59 UT |accessdate=2007-06-26] 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. However, later analysis shows the body is not affected by the pressures of solar radiation and must be a dense rocky body or at least regularly shaped. One hypothesis is that the object is a piece of lunar rock ejected by an impact. [cite web| url=http://home.gwi.net/~pluto/mpecs/6r1.htm| title=Pseudo-MPEC for 6R10DB9| author=Bill Gray| accessdate=August 16| accessyear=2007| ]

"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 September 14 to the NEOCP and subsequently removed with the explanation that it "was not a minor planet." [cite web |url=http://www.hohmanntransfer.com/news/0704.htm#news |title=Major News About Minor Objects, April 18, 2007 |accessdate=2007-06-27] However, the object was later confirmed to be minor planet.

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 approximately 200,000 miles.

June 14, 2007 Perigee

On June 14, 2007, 2006 RH₁₂₀ made its fourth and last perigee of its 2007 encounter. 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. A next potential near-Earth encounter will be 2028.

References and footnotes

ee also

*6Q0B44E - Another small Earth satellite, probably artificial
*3753 Cruithne - Another "Second Moon" candidate
*mpl|2002 AA|29 - Potential Earth-orbiting asteroid
*Natural satellite

External links

* [http://www.birtwhistle.org/Gallery6R10DB9.htm Great Shefford Observatory's 6R10DB9 images and background]
* [http://www.skyandtelescope.com/news/7067527.html Earth's "Other Moon" on SkyandTelescope.com]
* [http://echo.jpl.nasa.gov/ JPL Radar Astrometry Page]
* [http://home.gwi.net/~pluto/mpecs/6r1.htm Bill Gray's Pseudo-MPEC Page on 6R10DB9]
* [http://ssd.jpl.nasa.gov/horizons.cgi#top JPL Horizons ephemeris gererator] Change target body to "2006 RH120".