|Discovered by||Steward Observatory (691)|
|Discovery date||November 6, 1991|
|Uncertainty parameter 2|
|Earth MOID||0.0041420 AU|
|Dimensions||5–12 m (15–40 ft)|
On November 6, 1991, Scotti discovered a faint object which was designated 1991 VG soon after discovery. The object's heliocentric orbit was found to be very similar to Earth's orbit and it was found that it would make a close approach to Earth just a month after discovery (on December 5, 1991). Given such an Earth-like orbit, the dynamical lifetime of such an object is relatively short with the object quickly either impacting Earth or being perturbed by Earth onto a different orbit. The similarity of its orbit with Earth was also very difficult to explain from natural sources, with ejecta from a recent Lunar impact or non-gravitational perturbations such as the Yarkovsky effect having been suggested. More recently, the first Earth Trojan asteroid - 2010 TK7 has been identified and such objects could well be a source for objects like 1991 VG.
Possible monolithic structure
Since the discovery of 1991 VG, about 80% of small asteroids with absolute magnitudes (H) fainter than 22.0 (corresponding to sizes smaller than about 200 meters) which have had their lightcurve measured have rotation periods under 2 hours. Such rapid rotation rates are typically associated with asteroids that are monolithic bodies or welded conglomerates having sufficient intrinsic strength to counteraact centrifugal forces. More slowly rotating asteroids are sometimes gravitationally bound aggregates.
Possible artificial origin
The uncertainty of the object's origin, combined with rapid variation in the object's brightness in images obtained during its close passage with Earth in early December 1991, led to some speculation that 1991 VG might be artificial in origin. There was much speculation that it could be a rocket body from a satellite launched in the early 1970s when 1991 VG made its previous close approach with Earth. Earlier close approaches to Earth were before the start of the space age.
- "1991 VG". Minor Planet Center. 27 April 1992.
- "JPL Small-Body Database Browser: (1991 VG)" (last observation: 1992-04-27; arc: 173 days). Jet Propulsion Laboratory. Retrieved 2015-06-04.
- "ABSOLUTE MAGNITUDE (H)". NASA.
- satobs.org: James Scotti, Re: What is 1991 VG?
- jpl.nasa.gov, 1991 VG Earth Impact Risk Summary
- Steele, D. (1995). "SETA and 1991 VG". The Observatory 115: 78–83. Bibcode:1995Obs...115...78S.
- Hergenrother, C. W.; Whiteley, R. J. (2011). "A survey of small fast rotating asteroids among the near-Earth asteroid population". Icarus 214: 194. Bibcode:2011Icar..214..194H. doi:10.1016/j.icarus.2011.03.023.