A resonant family of dynamically cold small bodies in the near-Earth asteroid belt

TL;DR

This paper identifies a new, stable group of small near-Earth objects in 1:1 resonance with Earth, highlighting their potential for scientific study and impact risk, and discussing their possible role in Earth's natural satellite formation.

Contribution

It discovers and characterizes a previously unrecognized family of dynamically cold, Earth-resonant small bodies, including at least 10 members with unique orbital properties.

Findings

2013 BS45 is a stable Earth co-orbital asteroid.

The group includes at least 10 members with similar orbital parameters.

Some objects, like 2012 FC71, are in Kozai resonance, reducing impact risk.

Abstract

Near-Earth objects (NEOs) moving in resonant, Earth-like orbits are potentially important. On the positive side, they are the ideal targets for robotic and human low-cost sample return missions and a much cheaper alternative to using the Moon as an astronomical observatory. On the negative side and even if small in size (2-50 m), they have an enhanced probability of colliding with the Earth causing local but still significant property damage and loss of life. Here, we show that the recently discovered asteroid 2013 BS45 is an Earth co-orbital, the sixth horseshoe librator to our planet. In contrast with other Earth's co-orbitals, its orbit is strikingly similar to that of the Earth yet at an absolute magnitude of 25.8, an artificial origin seems implausible. The study of the dynamics of 2013 BS45 coupled with the analysis of NEO data show that it is one of the largest and most stable members of a previously undiscussed dynamically cold group of small NEOs experiencing repeated trappings in the 1:1 commensurability with the Earth. This new resonant family is well constrained in orbital parameter space and it includes at least 10 other transient members: 2003 YN107, 2006 JY26, 2009 SH2 and 2012 FC71 among them. 2012 FC71 represents the best of both worlds as it is locked in a Kozai resonance and is unlikely to impact the Earth. Objects in this group could be responsible for the production of Earth's transient irregular natural satellites.