Asteroid Belt 101: Definition, Origin, Shapes, and Misunderstanding

The asteroid belt is one of the most attractive regions in our solar system. This asteroid belt stretches quite wide from Mars orbit to Jupiter. Let’s discuss starting from the definiton.

asteroid belt

Definition of Asteroid Belt

In our solar system, there are actually two asteroid belts, the main asteroid belt and the Kuiper belt. The main asteroid belt is usually called the asteroid belt. Therefore, the asteroid belt we discussed this time is the main asteroid belt.

The asteroid belt is an area in our solar system that is located between the orbits of Mars and Jupiter consisting of chunks of space rocks (asteroids). Until now, the number of detected asteroids in the asteroid belt is 960,749 asteroids.

After knowing the meaning and location, we next discuss the origins.


In the early days of the formation of the solar system, dust and rocks surrounding the sun slowly fused to form a planet. This is caused by the gravitational force between the dust and the rock. But not all dust and rocks form a planet. The area of ​​dust and rock that did not form a planet is known as the asteroid belt today.

Scientists used to think that this asteroid belt was the remnants of a destroyed planet colliding with a comet or another planet. But it turns out after calculations, the total mass of the asteroid belt is not enough to form a terrestrial planet even small in size. According to NASA, the total mass of the asteroid belt is even smaller than the mass of our moon.

From this, the common thread can be drawn that the total mass of dust and rocks in the asteroid belt is very small, even much smaller than the mass of the moon. Besides, Jupiter’s large gravitational force prevents dust and small rocks to form a whole planet.

A terrestrial planet is a planet in which the majority is composed of solids and rocks. In our solar system, we have Mercury, Venus, Earth, and Mars. While the Jovian planet is a planet in which the majority is composed of gas and is generally giant. In the solar system, we have Jupiter, Saturn, Uranus, and Neptune.

Besides, it was also found that the chemical composition of the asteroids there were many differences. So this reinforces that the asteroid belt could not have originated from the destruction of one large object. This difference in the composition will be discussed in the asteroid types section.
Skip to the asteroid type

Then how about the size and shape of these asteroids?

Size and Shape

bentuk asteroid
Copyright: Emily Lakdawalla/Ted Stryk

Some asteroids have a size that is ‘large’. In the asteroid belt, it is estimated that there are 1.1-1.9 million asteroids with a diameter of more than 1 km and 16 of them have a diameter greater than 240 km. The three largest asteroids in the asteroid belt are Vesta, Pallas, and Hygiea, they even have diameters greater than 400 km. Besides, this area also has the dwarf planet Ceres which has a diameter of 950 km. Other smaller asteroids have irregular shapes and are even potatoes-shaped.

After knowing the size and shape, let’s discuss the types.

Asteroid Types

Asteroid Type C

The letter “C” comes from the word “carbonaceous” (containing carbon). It is the most common type of asteroid, around 75%. Very dark in color like charcoal.

Asteroid Type S

The letter “S” comes from the word “Siliceous” (containing silica). It is the second most common type of asteroid, around 17%. Many are found in the inner asteroid belt, and the further away from the sun the more rarely found. Contains nickel-iron mixed with iron-silica and magnesium-silica. Brighter color.

Asteroid Type M

The letter “M” comes from the word “Metallic”. Is the third most common type of asteroid. Bright enough color and composed of pure nickel-iron. Tends to be found in the middle of the asteroid belt.

Other Type Asteroids

Besides the main types above, there are also asteroids types A, D, E, P, Q, and R, but very rarely. Also, there are sub-types B, F, and G which are subtypes of type C.

If you pay attention, these asteroids are rich in natural resources. Therefore, there are many discussions and plans to be able to mine natural resources in these asteroids.

Also read
Nuclear Fusion: Future Energy Sources


medan asteroid
Copyright: LucasFilm

Ever seen a space scene like the one above? At first glance when mentioned asteroid belt, our mind usually made a picture like that right?

A space area like this might be interesting. But unfortunately, even though there are so many asteroids in the asteroid belt, we often forget that the asteroid belt is a very, very large area. The distance between the asteroids was estimated at hundreds of thousands of kilometers.

Therefore, when NASA engineers plan spacecraft routes they pass through the asteroid belt, they even do not think that the spacecraft will even fly close to one of the asteroids.


An asteroid belt is an area in our solar system that contains dust and space rocks (asteroids) located between the orbits of Mars and Jupiter. The asteroid belt is also often called the main asteroid belt because there is also another asteroid belt called the Kuiper belt. The size of the asteroids on the asteroid belt varies from the size of dust to hundreds of kilometers, with the majority having a diameter below one kilometer.

In film and animation, asteroid belts are often depicted as very dense. But in fact, the asteroid belt is very tenuous, the distance between the asteroids was up to hundreds of thousands of kilometers. Even so, the asteroid belt is still an interesting area in our solar system.

Stay curious.

Sources and References:

  1. The Asteroid Belt: Not What You Think! – SciShow Space
  2. Asteroid Belt: Facts & Formation – Space
  3. In Depth | Asteroids – NASA Solar System Exploration
  4. Basics of Space Flight | Section 1, Chapter 1 – NASA Solar System Exploration
  5. How Dense is the Asteroid Belt? – Universe Today

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