However, asteroids not in a tight co-orbital configuration with a planet can be temporarily captured for less than a full orbit; such objects have been named temporarily-captured fly-bys (TCF).
[7] In a 2017 follow-up to the 2012 simulation study which also considered an improved model of near-Earth asteroid populations, 40% of captured objects were TCF.
The combined number of TCO/TCF was found to be smaller than in the previous study, the maximum size of objects which can be expected to be orbiting Earth at any given moment was 0.8 m (2.6 ft).
As of March 2018[update], there is one confirmed example of a temporarily captured asteroid that didn't complete a full orbit, 1991 VG.
[15] The Earth can also temporarily capture defunct space probes or rockets travelling on solar orbits, in which case astronomers cannot always immediately determine whether the object is artificial or natural.
[16][3] In 2006, an object designated 6Q0B44E was discovered on a temporary satellite orbit, later its artificial nature was confirmed, but its identity is unknown.