Dynamical study of the Atira group of asteroids

• Published in: Monthly notices of the Royal Astronomical Society Vol. 458; no. 4; pp. 4471 - 4476
• Main Authors: Ribeiro, A. O., Roig, F., De Prá, M. N., Carvano, J. M., DeSouza, S. R.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01.06.2016
• Subjects: Asteroid collisions; Asteroids; Chaos theory; Collision avoidance; Earth; Earth orbits; Mercury; Orbitals; Orbits; Standard deviation; Star & galaxy formation; Venus; minor planets, asteroids: general
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw642

We study the dynamics of the group of Atira asteroids, characterized by aphelion distance Q < 0.983 au. This group has a significant observational bias, and their number is expected to be an order of magnitude larger than is known today. Due to their orbital configuration, these asteroids may represent a potential danger to the Earth. Here, we construct dynamical maps of the region between 0.2 and 0.98 au using a simple chaos indicator, the mean standard deviation in semimajor axis, and also analyse the behaviour of the real Atira orbits by means of the diffusion coefficient in semimajor axis. Our results indicate that Atira asteroids are located in the most unstable regions of the inner Solar system, and their stability is determined by close encounters and collisions with Mercury, Venus, and the Earth. A fraction of the known Atiras may represent a potential threat to the Earth over a few 105 yr of evolution. We found two islands of low-eccentricity stable orbits that might harbour a long-lasting sub-population of Atiras not yet observed.