HYG

The Hygiea family, often designated HYG in asteroid-family catalogs, is a collisional group of asteroids located in the outer region of the main belt. It is named after the largest member, 10 Hygiea, a large, dark, carbonaceous (C-type) asteroid that serves as the family's benchmark.

Members of the Hygiea family share similar orbital elements, clustered in proper semi-major axis, eccentricity, and inclination. This dynamical grouping is interpreted as resulting from the fragmentation of a common parent body in a past collisional event. The family is characteristic of low albedo, carbon-rich material and lies in the outer main belt around roughly 3.1 astronomical units from the Sun, with relatively modest inclinations.

10 Hygiea itself has a diameter of about 433 kilometers, making it one of the larger bodies in the main belt and a natural reference for the family. The remaining members are substantially smaller fragments, ranging from tens of kilometers down to much smaller debris, whose orbits have evolved under gravitational resonances and non-gravitational forces such as the Yarkovsky effect.

The age of the Hygiea family is uncertain and debated, with estimates spanning hundreds of millions to over a billion years, depending on dynamical models and the influence of resonances. Studying the HYG family helps researchers understand asteroid collisional histories, the distribution of primitive, carbon-rich material in the early solar system, and the long-term dynamical evolution of outer-belt objects.

See also: 10 Hygiea; asteroid family; list of asteroid families.