Kirkwood gap in the context of Apollo asteroid

10 Hygiea is a large asteroid located in the outer main asteroid belt between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observatory of Capodimonte in Naples, Italy. It was named after Hygieia, the Greek goddess of health. It is the fourth-largest main-belt asteroid by both volume and mass, with a mean diameter of 433 km (269 mi) and a mass constituting 3% of the main asteroid belt's total mass.

Hygiea has a nearly spherical shape, with two known craters about 100 and 180 km (62 and 112 mi) in diameter. Because of its shape and large size, some researchers consider Hygiea a possible dwarf planet. Hygiea has a dark, carbonaceous surface consisting of hydrated and ammoniated silicate minerals, with carbonates and water ice. Hygiea's subsurface likely contains a large fraction of water ice. These characteristics make Hygiea very similar to the main-belt dwarf planet Ceres, which suggests the two objects have similar origins and evolutionary histories.

An asteroid family is a population of asteroids that share similar proper orbital elements, such as semi-major axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An asteroid family is a more specific term than asteroid group whose members, while sharing some broad orbital characteristics, may be otherwise unrelated to each other.

The Koronis or Koronian family (FIN: 605), also known as the Lacrimosa family, is a very large asteroid family of stony asteroids, located in the outer region of the asteroid belt. They are thought to have been formed at least two billion years ago in a catastrophic collision between two larger bodies. The family is named after 158 Koronis, and the largest known member (208 Lacrimosa) is about 41 km (25 mi) in diameter. The Koronis family travels in a cluster along the same orbit. It has 5949 members.

This family has two subfamilies. The Karin family (FIN: 610) was formed remarkably recently in a catastrophic collision (destroying the parent body), with an estimated age of 5.72 million years. The Koronis(2) family (FIN: 621) with 246 members is the other. It formed 15 million years ago by a non-catastrophic collision with 158 Koronis.

The Themis family (adj. Themistian; FIN: 602) is a family of carbonaceous asteroids located in the outer portion of the asteroid belt, at a mean distance of 3.13 AU from the Sun. It is one of the largest families with over 4700 known members, and consists of a well-defined core of larger bodies surrounded by a region of smaller ones. The collisional Themis family is named after its parent body, the asteroid 24 Themis, discovered on 5 April 1853 by Italian astronomer Annibale de Gasparis.

Commensurability is the property of two orbiting objects, such as planets, satellites, or asteroids, whose orbital periods are in a rational proportion.

Examples include the 2:3 commensurability between the orbital periods of Neptune and Pluto, the 3:4 commensurability between the orbital periods of the Saturnian satellites Titan and Hyperion, the orbital periods associated with the Kirkwood gaps in the asteroid belt relative to that of Jupiter, and the 2:1 commensurability between Gliese 876 b and Gliese 876 c.