Eurybates family

Lore & Background

The Eurybates family is a group of physically related asteroids created by a collision with an original larger asteroid, with the fragments continuing on similar orbits. This distinguishes it from a mere dynamical group, whose members share orbits only due to gravitational interactions with planets. All members of the Eurybates family are dark C-type asteroids with albedos of around 0.05.

The family is considered catastrophic because 3548 Eurybates, its largest member, constitutes only a quarter of the family's mass. The family's exact age is not known, though it has been constrained to under 3.7 billion years; simulations show that 3548 Eurybates's satellite Queta would be very unlikely to survive to the modern day if it had formed earlier. A more recent study suggested an age of 1.05±0.36 billion years based on the modeled rate of family members escaping the Trojan region over time.

As part of the Jupiter Trojan dynamical group, the family resides in an orbital resonance with Jupiter, staying about 60 degrees ahead of or behind the planet at the Lagrange points L4 and L5. The Eurybates family belongs to the leading cloud around L4, the Greek camp.

Reader's Guide

The Eurybates family holds significance as a catastrophic collisional family within the Jupiter Trojan population, providing insight into the violent history of the outer Solar System. Its status as a family of at least 218 known asteroids, all dark C-type bodies with low albedos, underscores the nature of the original impact event that shattered a larger parent body. The fact that 3548 Eurybates itself accounts for only a quarter of the family's mass indicates a highly disruptive collision, leaving many fragments on similar orbits.

The family's age constraints—under 3.7 billion years from satellite survival simulations, and a more recent estimate of 1.05±0.36 billion years from escape modeling—highlight ongoing efforts to date such ancient events. The presence of the satellite Queta around 3548 Eurybates serves as a key temporal marker. As part of the Greek camp of Jupiter Trojans, the Eurybates family contributes to understanding the dynamical evolution of asteroids trapped at Lagrange points. Its legacy lies in demonstrating how collisional families can form within larger dynamical groups, offering a window into the processes that have shaped the asteroid belt and Trojan populations over billions of years.

Did You Know?

• The Eurybates family contains at least 218 known asteroids.
• Its largest member, 3548 Eurybates, is 64 kilometres across.
• The family is part of the Greek camp, the leading cloud of Jupiter Trojans at the L4 Lagrange point.
• The satellite Queta orbits 3548 Eurybates and helps constrain the family's age to under 3.7 billion years.