Ennomos family

Lore & Background

The Ennomos family is a collisional asteroid family, meaning its members are fragments from a collision with the original larger asteroid 4709 Ennomos. All members share similar orbits, a result of the breakup event. The family is considered non-catastrophic because 4709 Ennomos itself constitutes a majority of the family's total mass, unlike catastrophic families where the largest fragment is a small fraction of the original body. All members are dark, assumed to be C-type asteroids, with albedos around 0.09.

The family resides within the Jupiter trojans, a dynamical group of asteroids that share Jupiter's orbit, staying about 60 degrees ahead of or behind the planet at the Lagrange points L4 and L5. The Ennomos family is part of the trailing cloud around L5, known as the Trojan camp. This dual membership means the asteroids are both fragments of a single collision and part of a larger gravitational concentration of objects.

The trojan 1867 Deiphobus is a large interloper in the Ennomos family's orbital region. A 2024 study found that Deiphobus has its own overlapping family, with a slightly higher inclination. As a result, some members currently included as part of the Ennomos family may actually belong to the Deiphobus family, and vice versa, introducing uncertainty into the family's membership.

Reader's Guide

The Ennomos family holds significance as a distinct collisional family within the Jupiter trojan population, demonstrating that not all asteroid families result from catastrophic disruption. Its non-catastrophic nature, where the parent body 4709 Ennomos retains most of the family's mass, provides a contrast to typical families and offers insight into the outcomes of lower-energy collisions. The family's location in the L5 Trojan camp ties it to the broader dynamical group of Jupiter trojans, which are important for understanding the solar system's formation and the distribution of primitive material. The presence of the interloper 1867 Deiphobus and its overlapping family complicates the family's boundaries, highlighting the challenges in distinguishing between true collisional fragments and objects that merely share similar orbits due to gravitational interactions. This overlap, identified in a 2024 study, means that the exact membership of the Ennomos family remains uncertain, with some asteroids potentially belonging to either family. The family's legacy lies in its contribution to the study of asteroid family formation and the dynamics of the Trojan clouds, serving as a case study for non-catastrophic collisions and the interplay between collisional and dynamical groupings.

Did You Know?

• The Ennomos family is named for its largest member, 4709 Ennomos, which is 81 km across.
• It is a non-catastrophic asteroid family, meaning 4709 Ennomos makes up a majority of the family's total mass.
• The family lies in the trailing cloud around Jupiter's L5 Lagrange point, known as the Trojan camp.
• The trojan 1867 Deiphobus is a large interloper with its own overlapping family, causing potential membership confusion.