Orbital Dynamics of 2020 AV2: the First Vatira Asteroid

Abstract

Vatira-class near-Earth objects (NEOs) have orbits entirely interior to the orbit of Venus with aphelia $0.307<Q<0.718$ AU. Recently discovered asteroid 2020 AV$_2$ by the Zwicky Transient Facility on 4 January 2020 is the first known object on a Vatira orbit. Numerical integrations of 2020 AV$_2$'s nominal orbit show it remaining in the Vatira region for the next few hundred kyr before coupling to Venus and evolving onto an Atira orbit (NEOs entirely interior to Earth's orbit with $0.718<Q<0.983$ AU) and eventually scattering out to Earth-crossing. The numerical integrations of 9900 clones within 2020 AV$_2$'s orbital uncertainty region show examples of Vatira orbits trapped in the 3:2 mean-motion resonance with Venus at semimajor axis $a\approx0.552$ AU that can survive on the order of a few Myr. Possible 2020 AV$_2$ orbits also include those on Vatira orbits between Mercury and Venus that only rarely cross that of a planet. Together the 3:2 resonance and these rarely-planet-crossing orbits provide a meta-stable region of phase space that are stable on timescales of several Myr. If 2020 AV$_2$ is currently in this meta-stable region (or was in the past), that may explain its discovery as the first Vatira and may be where more are discovered.