The orbital clusters among the near-Earth asteroids

Abstract

ABSTRACT Fifteen orbital clusters (associations) were identified among ${\sim }20\, 000$ near-Earth asteroids (NEAs). All associations were found with a high statistical reliability using a single linkage cluster analysis algorithm and three orbital similarity functions. The identified groups constitute a small fraction (4.74 per cent) of the entire sample. Notwithstanding, they may be hazardous to Earth and its inhabitants. As with meteoroid streams, every year Earth comes very close to the orbits of each association. In two cases (2008TC3 and 2017FU102), the distance between the asteroid’s orbit and Earth’s orbit was shorter than Earth’s radius. Among the members of the identified associations, we found 331 objects larger than the Chelyabinsk asteroid and all of them approach Earth’s orbit at a distance smaller than 0.05 au. Two of the identified groups, (4179) Toutatis and (251430) Itokawa, support the hypothesis regarding the catastrophic origins of the asteroids Toutatis and Itokawa through violent collisions. This study does not focus on the origin of the NEA associations, but rather focuses on tracing the associations. Regardless of their origin, the identified groups pose a serious threat to Earth. Hence, to facilitate their monitoring of we calculated coordinates of the theoretical radiants and the calendar dates of their potential activity.