Dynamical evolution of near-Earth asteroid 1991 VG

Abstract

The discovery of 1991 VG on 1991 November 6 attracted an unprecedented amount of attention as it was the first near-Earth object (NEO) ever found on an Earth-like orbit. At that time, it was considered by some as the first representative of a new dynamical class of asteroids, while others argued that an artificial (terrestrial or extraterrestrial) origin was more likely. Over a quarter of a century later, this peculiar NEO has been recently recovered and the new data may help in confirming or ruling out early theories about its origin. Here, we use the latest data to perform an independent assessment of its current dynamical status and short-term orbital evolution. Extensive N-body simulations show that its orbit is chaotic on time-scales longer than a few decades. We confirm that 1991 VG was briefly captured by Earth's gravity as a minimoon during its previous fly-by in 1991-1992; although it has been a recurrent transient co-orbital of the horseshoe type in the past and it will return as such in the future, it is not a present-day co-orbital companion of the Earth. A realistic NEO orbital model predicts that objects like 1991 VG must exist and, consistently, we have found three other NEOs -2001 GP 2 , 2008 UA 202 and 2014 WA 366 -which are dynamically similar to 1991 VG. All this evidence confirms that there is no compelling reason to believe that 1991 VG is not natural.

Exploring the dynamical evolution of minimoon 2020 CD3 in a circular restricted three-body problem framework

“…figure 9, this object has been switching mode between quasi-satellite and minimoon on numerous occasions. This phenomenon was already mentioned in previous studies about 1991 VG and 2020 CD3 that become recurrent minimoons and Earth's co-orbital objects [13,14,6]. These objects are coming from a population that is frequently trapped in 1:1 mean-motion resonance with Earth and affected by Kozai-Lidov mechanism.…”

Discovering Earth’s transient moons with the Large Synoptic Survey Telescope

“…Following the discovery and characterisation of Earth's temporary-captured satellite 2006 RH 120 (Kwiatkowski et al, 2009), Granvik et al (2012) were the first to propose that there is a population of small asteroids in orbit around the Earth at any given time. Further evidence of temporarily-captured satellites come from, e.g., backwards orbit integration of the asteroid 1991 VG (de la Fuente Marcos & de la Fuente Marcos, 2018), the discovery of the meteor EN130114 originating from a geocentric orbit (Clark et al, 2016), and a candidate temporarily-captured satellite detected by the Space Surveillance Telescope (Lue et al, 2019). Natural temporarily-captured satellites include both temporarily-captured orbiters (TCOs), that make at least one equivalent of a revolution around the Earth while being captured, and temporarily-captured flybys (TCFs), that make less than one equivalent of a revolution while being captured.…”