The Formation of the Collisional Family around the Dwarf Planet Haumea

TL;DR

This paper proposes that the unique features of the Haumea system resulted from a graze-and-merge giant collision, explaining its satellites, family members, and water ice spectral signature, which differ from typical asteroid families.

Contribution

It introduces a novel collision model for Kuiper Belt objects, specifically a graze-and-merge impact, to explain Haumea's distinctive characteristics.

Findings

Haumea's family formed from a graze-and-merge collision.

Giant collisions in the Kuiper Belt are more common than previously thought.

The collision explains Haumea's rapid rotation, elongated shape, and water ice features.

Abstract

Haumea, a rapidly rotating elongated dwarf planet (~ 1500 km in diameter), has two satellites and is associated with a "family" of several smaller Kuiper Belt objects (KBOs) in similar orbits. All members of the Haumea system share a water ice spectral feature that is distinct from all other KBOs. The relative velocities between the Haumea family members are too small to have formed by catastrophic disruption of a large precursor body, which is the process that formed families around much smaller asteroids in the Main Belt. Here we show that all of the unusual characteristics of the Haumea system are explained by a novel type of giant collision: a graze-and-merge impact between two comparably sized bodies. The grazing encounter imparted the high angular momentum that spun off fragments from the icy crust of the elongated merged body. The fragments became satellites and family members. Giant collision outcomes are extremely sensitive to the impact parameters. Compared to the Main Belt, the largest bodies in the Kuiper Belt are more massive and experience slower velocity collisions; hence, outcomes of giant collisions are dramatically different between the inner and outer solar system. The dwarf planets in the Kuiper Belt record an unexpectedly large number of giant collisions, requiring a special dynamical event at the end of solar system formation.