Asteroid Systems: Binaries, Triples, and Pairs

TL;DR

This paper reviews recent discoveries and formation theories of binary, triple, and paired asteroid systems, emphasizing rotational fission and collisional origins based on observational evidence.

Contribution

It synthesizes observational data and proposes a unifying paradigm explaining asteroid system formation through rotational fission and collision processes.

Findings

Small binaries form by rotational fission driven by YORP effect.

Large binaries with small satellites likely result from large collisions.

Discovery of new asteroid pairs and triples supports the unifying formation paradigm.

Abstract

In the past decade, the number of known binary near-Earth asteroids has more than quadrupled and the number of known large main belt asteroids with satellites has doubled. Half a dozen triple asteroids have been discovered, and the previously unrecognized populations of asteroid pairs and small main belt binaries have been identified. The current observational evidence confirms that small (<20 km) binaries form by rotational fission and establishes that the YORP effect powers the spin-up process. A unifying paradigm based on rotational fission and post-fission dynamics can explain the formation of small binaries, triples, and pairs. Large (>20 km) binaries with small satellites are most likely created during large collisions.