ACM - Asteroids LESSON

Asteroids

Asteroids are small, rocky objects that orbit the Sun. However, they are too small to be considered a planet. The majority of asteroids are located between Mars and Jupiter in an area known as the Asteroid Belt. Although there are over one million asteroids located in the Asteroid Belt, not all asteroids are located here. There are a small amount of asteroids found in other places in our solar system. When asteroids pass close to Earth, we call these "near-earth objects". In the image below, you can see that asteroids come in all shapes and sizes.

asteroids of various sizes and shapes

Go through the timeline below to learn more about asteroids!

 

Asteroid Classifications
Main Asteroid Belt
  • Asteroids located in orbit between Mars and Jupiter.
  • Jupiter's gravity brought an end to the formation of planetary bodies in this region and caused the small bodies to collide with one another, shattering them into the asteroids located in the belt today.
Trojans
  • Asteroids that share an orbit with a larger planet but do not interfere with each other.
  • The gravitational pull from the sun and the planet are balanced by a Trojan's tendency to otherwise fly out of the orbit.
  • The Jupiter Trojans form the most significant population of Trojan asteroids.
  • There are Mars and Neptune Trojans.
  • NASA announced the discovery of an Earth Trojan in 2011.
Near-Earth Asteroids
  • Asteroids or small objects that pass close to Earth.
  • An estimated 10,003 asteroids have passed close by Earth.
  • 1,409 of them were classified as potentially hazardous that could pose a threat to Earth.

In the image below, you can see the Asteroid Belt (White) and the Trojans (Green).

Asteroid Belt and Trojans

Composition Classes

Asteroids can be classified into three main types: C-, S-, and M-types. These classifications are based on the composition of the asteroid.

  • C-type asteroids are known as chondrite. They are most common, probably consist of clay and silicate rocks, and are dark in appearance. These asteroids are the oldest ones in the solar system.
  • S-type asteroids are known as "stony". They are made up of silicate materials and nickel-iron.
  • M-type asteroids are metallic and made of nickel-iron composition.

The asteroids' compositional differences are related to how far from the Sun they formed. Some experienced high temperatures after they formed and partly melted, with iron sinking to the center and forcing basaltic (volcanic) lava to the surface. Only one such asteroid, Vesta, survives to this day.

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