Asteroids
Asteroids are the rocky remnants of the formation of a solar system (our own formed 4.6 billion years ago). In worldbuilding, asteroids and asteroid belts often serve as hiding places, natural barriers, military bases, artificial habitats, and mining areas. They may be captured (naturally or artificially) by a larger celestial body, they may be rogue and floating through space on their own, or they may be part of an asteroid belt. Hollowed asteroids may be used as space stations or space colonies.

Synonyms: space rocks |
Example Mythonyms: 4035 Porthos, 5933 Victor |

Designing Fictional Asteroids
Archetypes
Overview
Composition
Asteroids can be largely divided into 3 main groups based on composition: C-type, S-type, and M-type (while these are the most common, other types of asteroids do exist, such as the rare and mysterious O-type).
- C-type (chondrite): composed mainly of silicate and clay. These generally have a darker appearance and are some of the most ancient objects in our solar system.
- S-type (“stony”): composed of silicate and nickel-iron.
- M-type (metallic): composed mostly of nickle-iron.


Is an ancient spaceship or cosmic horror hidden in an asteroid of your world? It will likely be encased in a C-type asteroid.
Are the inhabitants of your world mining the asteroid belt for construction metals? They will likely be on the search for M-type asteroids.
Location
Asteroids in our own solar system are also divided into 3 types based on location: Main Belt Asteroids, Trojans, and Near-Earth Asteroids.
- Main Belt Asteroids: The main asteroid belt is a ring-shaped collection of asteroids encircling the sun between the orbits of Jupiter and Mars. It is home to between 1.1 and 1.9 million asteroids. The largest four asteroids at this location are Ceres, Vesta, Pallas, and Hygiea.
- Trojans: The trojans are a collection of asteroids that occupy the L4 and L5 Lagrange points of Jupiter. Generally, the asteroids at the L4 Lagrange point are all named after Greek heroes of the Trojan War and are referred to as the Greek Camp, while the asteroids at Jupiter’s L5 Lagrange point are named after Trojan heroes and are referred to as the Trojan Camp. There are two exceptions to this nomenclature: Hektor is a Trojan hero and asteroid that exists in the Greek Camp at L4, and Patroclus is a Greek hero and asteroid that exists in the Trojan Camp at L5. They were named before the Greek/Trojan camp rule was established and astronomers refer to them as ‘spies.’ Somewhat confusingly, asteroids of both the Trojan camp and the Greek camp are considered Trojan asteroids, and asteroids trapped at the Lagrange points of other celestial bodies may also be called trojans (for example, Mars’ Trojans).
- Near Earth Asteroids: near earth asteroids are asteroids that either cross, or come near to Earth’s orbit. It is these asteroids that poise the greatest threat to our planet.

Lagrange point: a point in space relative to two orbiting bodies where the gravitational forces can hold an object in that same relative position. Lagrange points are widely thought of as being perfect locations for space stations and are often the sites of asteroid accumulation.
Asteroids will sometimes have their own companion moon, or smaller asteroid orbiting them. Occasionally two similarly sized asteroids will orbit each other.
Asteroid Impacts
Asteroid Impacts
Asteroid impacts are used in a variety of ways in worldbuilding. Often the crater of such an event serves as a location of interest. Asteroids may bring alien life with along with them. And, given our own world’s history with the dinosaurs, asteroids often play a role in extinction and/or catastrophic events.

