Asteroids, also called minor planets, are the rocky remains left over around 4.6 billion years ago from the early development of our solar system.
They are too small to be considered planets. Often classified as planetoids or minor planets. There are millions of asteroids, from hundreds of miles to many feet. Generally, the mass of all asteroids is smaller than Earth’s moon.
The estimated reported count for asteroids is: 957,703.
Some of this ancient space debris can be found in the primary asteroid belt surrounding the earth between Mars and Jupiter. Asteroids vary in size from Vesta — the largest with a diameter of around 329 miles (530 kilometers) — to bodies smaller than 10 meters (33 feet) wide. The total mass of all the combined asteroids is less than that of Earth’s Moon.
Most asteroids are irregularly shaped, but a few are almost spherical, and are often cratered or pitted. As they in elliptical orbits revolve around the earth, the asteroids often rotate, often very erratically, tumbling as they move. More than 150 asteroids (some have two moons) are known to have a small companion earth. There are also binary asteroids (double) in which two rocky bodies of roughly equal size circle each other, as well as triple asteroid systems.
The three broad composition classes of asteroids are C-, S-, and M-types.
- The C-type (chondrite) asteroids are most common, probably consist of clay and silicate rocks, and are dark in appearance. …
- The S-types (“stony”) are made up of silicate materials and nickel-iron.
- The M-types are metallic (nickel-iron).