Orbital dynamics of 2020 AV2: the first Vatira asteroid

Abstract

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 AV2 by the Zwicky Transient Facility on 2020 January 4 is the first known object on a Vatira orbit. Numerical integrations of 2020 AV2’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 AV2’s orbital uncertainty region show examples of Vatira orbits trapped in the 3:2 mean-motion resonance with Venus at semimajor axis a ≈ 0.552 au that can survive on the order of a few Myr. Possible 2020 AV2 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 is stable on time-scales of several Myr. If 2020 AV2 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.