2006 RH120

Discovery

was discovered on 14 September 2006 by Eric Christensen with the 27 in Schmidt camera of the Catalina Sky Survey in Arizona. "6R10DB9" Preliminary orbital calculations indicated it was captured by Earth's gravity from solar orbit of a period of about 12 months, which is similar to that of many spent rocket boosters dating to the Apollo program of the 1960s and early 1970s. 6R10DB was assigned the designation on 18 February 2008.

Origin

Some controversy existed regarding the origin of the object. Upon discovery, it was not given a formal name because its spectrum was consistent with the white titanium-oxide paint used on Saturn V rockets, which meant it could be 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, discovered a month earlier, was also thought to be artificial. Its status as a satellite was also debated, with A. W. Harris of the Space Science Institute commenting, "Claiming some bit of fluff in a temporary looping orbit to be a 'satellite', with all the baggage that term carries, is mere hype". Radar observations strongly suggest that the object is a natural body.

Orbit

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. In 2023, was identified as a possible dark comet. Dark comets are asteroids that exhibit comet-like acceleration, but visually appear as asteroids, with no coma or tail. Astronomers who study dark comets believe the acceleration is caused by outgassing on the sunlit side.

made four Earth orbits of about three months each with perigee (closest approach to Earth) on 11 September 2006, 3 January 2007, 25 March 2007, and 14 June 2007. During the 12-month capture from July 2006 to July 2007 when it was inside of Earth's Hill sphere, it stayed within 0.0116 AU of Earth. It was ejected after the 14 June 2007 perigee when it dipped inside the Moon's orbit to a distance of 276840 km. became an Apollo-class asteroid in June 2007 as it was escaping Earth's Hill sphere. Though it was outside of Earth's Hill sphere, the geocentric orbital eccentricity was not greater than 1 until 17 September 2007.

It is now in solar orbit as an Amor-class asteroid with an orbit completely outside of Earth's orbit. As of 2022, this object is 1.7 AU from Earth on the other side of the Sun and was not less than 1 AU from Earth until March 2025.

Future events

Around 18 August 2028 (±3 days) it will pass Earth with a relative velocity of 136 m/s and will then pass Earth with a relative velocity of 784 m/s around 9 October 2028 as it speeds up for a November 2028 perihelion passage (closest approach to the Sun and when an object moves fastest in its orbit). For comparison, on 13 April 2029, asteroid 99942 Apophis will pass Earth at a relative speed of 7.4 km/s.

has a 1-in-200 (0.5%) chance of Earth impact on 8 February 2044 and would impact with a harmless 1 kiloton of energy if it did impact. (The Chelyabinsk meteor released about 440 kt of energy.) JPL Horizon's nominal orbit has the asteroid passing 0.009 AU from Earth on 9 January 2044 (30 days before the virtual impactor). As a result of a 281 day observation arc and radar observations, JPL's solution accounts for non-gravitational forces as the multi-decade motion of a very small object is greatly affected by solar heating.

14 June 2007 perigee

On 14 June 2007, made its fourth and last perigee of the most recent Earth encounter. It was 0.72 lunar distances at closest, with an apparent magnitude of 18.5–19.0. Astronomers at JPL Goldstone in California made radar astrometry measurements on 12, 14 and 17 June 2007.

is listed as part of the Near-Earth Object Human Space Flight Accessible Targets Study (NHATS).

References

References

1. [[Wayback Machine
2. archive.ph: [https://archive.today/20121213133329/http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2006RH120 JPL Epoch 2012 = Apollo]
3. archive.ph: [https://archive.today/20150224153834/http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2006RH120 Epoch Jan 2007 = Aten with a=0.99au]
4. Great Shefford Observatory. "2006 RH120 ( = 6R10DB9) – A second moon for the Earth?".
5. "Distant Artificial Satellites Observation (DASO) Circular No. 68, 2006 Sept. 17, 16:59 UT".
6. "Major News About Minor Objects, April 18, 2007".
7. Spectrum measured by Carl Hergenrother and Rob Whitely of the University of Arizona.
8. Yeomans, Don. (April 2010). "Is Another Moon Possible?". Astronomy.
9. [[The Guardian]], Spacewatch, 6 September 2006
10. Roger W. Sinnott. (17 April 2007). "Earth's "Other Moon"". Sky & Telescope.
11. Dr. Lance A. M. Benner. (20 June 2007). "6R10DB9 Planning". JPL/NASA Asteroid Radar Research.
12. Bill Gray. ""Pseudo-MPEC" for 6R10DB9".
13. Seligman, Darryl Z.. (2023-02-15). "Dark Comets? Unexpectedly Large Nongravitational Accelerations on a Sample of Small Asteroids". The Planetary Science Journal.
14. (2025-05-01). "Dark Comets". Scientific American.
15. "2006 RH120".