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Asteroids are small rocky objects that orbit the Sun. Though they orbit the Sun just like planets, they are very small in comparison, and sometimes they are referred to as minor planets.
Key Facts & Summary
- Asteroids are rocky, airless remnants left over from the early formation of our Solar System, about 4.6 billion years old.
- There are over 900.000 confirmed asteroids in the Solar System, and more and more are found each day.
- There is a region in space where most asteroids are situated. It is called the asteroid belt – a region between the orbits of Mars and Jupiter.
- Asteroids can be found almost anywhere, they are located even in the orbital path of planets. This means that the asteroid and the planet follow the same path around the Sun.
- Even Earth has such asteroids that follow us around.
- No two asteroids are alike! This is because they formed in different locations at different distances from the Sun.
- Asteroids aren’t all round like planets. They have jagged and irregular shapes, often resembling a potato.
- While some asteroids are hundreds of miles in diameter, others are as small as pebbles. In fact, the vast majority of asteroids are very very small.
- The dwarf planet Ceres is also an asteroid, one of the biggest ever found.
- Asteroids are made out of different types of rock, but some have clays or metals, such as nickel and iron.
- Some asteroids are merely piles of rubble held together by gravity.
- There are many different types of asteroids, but among the most important ones are the C-type, S-type, and M-type.
- Asteroids are classified based on how much light they reflect and their chemical composition.
- Apart from Ceres, some of the largest asteroids in the Solar System are Vesta, Pallas, and Hygiea.
In the 18th century, a German astronomer by the name of Johann Titius was convinced that there was a planet between Mars and Jupiter.
His belief quickly captured the interest of other astronomers and they all started to search for this missing planet in 1800. Later, an Italian astronomer, Giuseppe Piazzi discovered Ceres, and then Pallas.
Everyone was very enthusiastic and they started searching for more and more. As they continued their hunt for planets, they discovered innumerable objects, some small, some big, and they realized that these weren’t planets. Since then, everyone started to refer to the little objects, as asteroids.
When the Solar System was young, dust and rock were pulled together by gravity giving birth to the planets. Some debris was left alone to float around the Sun.
The region between Mars and Jupiter later became what we today now know as the asteroid belt. Some believe that these asteroids are actually the remnants of a destroyed planet.
However, scientists have calculated the entire mass of these asteroids, and it is less than that of our Moon, which is very small compared to a planet. Because of this, many believe that the asteroids are simply objects kept in place, stopped from blending with other planets due to gravitational interactions with the planet Jupiter.
Different Types of Asteroids
There are many different kinds of asteroids. Asteroids are classified by how much light they reflect and their chemical composition. Here are some examples:
- C-type Asteroids
These asteroids make up for around 75% of the asteroid belt. The initial C stands for carbon. C-type asteroids have dark surfaces, almost coal-black in appearance
- S-type Asteroids
These asteroids make up around 17% of the asteroid belt. They are located mostly in the inner asteroid belt, and their numbers dwindle farther out. The initial S stands for silicaceous. They are bright asteroids composed of metallic nickel-iron mixed with magnesium-silicates.
- M-type Asteroids
These asteroids are the rarest in the Solar System. The initial M stands for metallic. They are relatively bright and they are mostly composed out of pure nickel-iron. Most of them reside in the middle of the asteroid belt.
No two asteroids are alike! This is because they formed in different locations at different distances from the Sun. Asteroids aren’t all round like planets. They have jagged and irregular shapes, often resembling a potato.
While some asteroids are hundreds of miles in diameter, others are as small as pebbles. In fact, the vast majority of asteroids are very very small.
There are around 16 detected asteroids with diameters greater than 150 mi / 240 km. Some of the largest asteroids are Ceres, Pallas, Vesta, Hygiea.
Ceres is the biggest of them all, having a diameter of around 590 mi / 950 km. The other three largest asteroids have diameters of around 250 mi / 400 km.
Due to its size and composition, Ceres is also considered a dwarf planet. It may contain water and who knows, maybe even life!
- Ceres is the first asteroid ever discovered, and the largest even to this day!
- Asteroid means “starlike”, this is because many astronomers thought in the beginning that they resembled stars.
- There are millions of asteroids in the asteroids belt, many of them are more than half a mile across. However, there are plenty more than that but they are very small.
- Asteroids are grouped into families! This is because they have a similar age. The Karin family, for example, is believed to have formed around 5.7 million years ago from a single object after a collision.
- If you could stand on an asteroid, you wouldn't be able to see the other ones because they are very far apart from one another, not like in the movies.
The Asteroid Belt
This is where most of the asteroids reside, between Mars and Jupiter. The asteroids here are made out of rock, stone, iron, nickel metals, and carbon-rich materials.
The asteroids that are the farthest away from the belt have even ice or water. Many asteroids here are sometimes referred to as planetoids, this where the dwarf planet Ceres resides.
Though in many movies asteroids are depicted as being very close to each other and very dangerous for ships, it is actually quite the opposite.
The average distance between asteroids in the belt is usually at around 600,000 mi / 1 million km. A spacecraft can safely travel there and explore.
The Asteroid Belt in the Future
The asteroids belt has existed for billions of years and it will continue to exist for just a couple of millions of years. This is because our Sun will near the end of its life in around 5 to 6 million years.
When this will happen, the Sun’s light will shatter the asteroid belt. This powerful “last light” of the Sun will radiate and warm up the asteroids, destroying them.
Did you know?
- One of the youngest asteroids families is called the Datura family. It dates at just 53.000 years old.
- Asteroids are very important for scientists since they can offer lots of information about the history of the planets and the Sun.
- Meteorites are tiny pieces of asteroids that flow through a planet’s atmosphere. Some of them reach the surface, but most of them are destroyed in the atmosphere.
- The extinction of the dinosaurs is largely attributed to an asteroid impact. These impacts happen, but not very often. However, we can now safely detect these asteroids and prevent them from hurting us.