What is the asteroid belt? | Space


This is the inner part of our solar system, from the sun to the 5th planet, Jupiter. In this illustration, the asteroid belt is the white donut-shaped cloud. Image via Wikimedia Commons.

Meet the Asteroid Belt, a place in our solar system where small bodies – mostly rocky and some metallic – orbit the sun. These little worlds are also sometimes called minor planets. They mainly move between the orbits of the fourth planet Mars and the fifth planet Jupiter. Astronomers once thought they were all that was left of a rocky planet, long torn apart by the gravity of Jupiter. Now, most astronomers now think the asteroid belt is just rubble that Jupiter’s gravity prevented from merging into a planet. So, asterids are probably just leftovers from the ordinary processes that created our solar system 4.6 billion years ago.

Their name, asteroid, ways like a star. They got this name because in the early 1800s, when the first asteroids were discovered, astronomers thought they looked like stars. And yet their movement in front of the background of the stars, caused by their proximity to us, showed them to be something other than stars.

Measurements of the amount of matter in the asteroid belt suggest that it contains roughly enough matter – combined together – to form a body smaller than Earth’s moon.

Made up of about one to two million asteroids over half a mile (about one kilometer) in diameter, plus millions of smaller asteroids, the asteroid belt contains objects that vary widely in size. The smallest are probably no bigger than pebbles. The largest object in the asteroid belt was also the first to be discovered, in 1801. It is 1 Ceres, which measures some 587 miles (945 km). Ceres is also classified as a dwarf planet by the International Astronomical Union.

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A round world with many craters.  In a crater, there are 2 very bright points.
This orthographic projection shows the largest body in the asteroid belt – 1 Ceres, discovered in 1801 – now classified as a dwarf planet by the International Astronomical Union. Ceres is one of the many Main Belt objects visited by spacecraft. This composite image comes from the Dawn spacecraft, still the only Earth spacecraft to have put the first body of our solar system into orbit (Vesta, 2011 to 2012), then into orbit a second (Ceres, arrived in 2015). Do you see the 2 luminous points of the Occator crater? They spawned speculation about alien life on Ceres, but turned out to be salt deposits. This image is taken from views taken by Dawn during her low-altitude map orbit, approximately 240 miles (385 km) above the surface. Image via NASA.

Outer space is vast. And so, although there are several million (maybe billions) of objects in the asteroid belt, the average distance between them is 600,000 miles (about one million km). This means that spacecraft can traverse the asteroid belt without colliding with any asteroids, although, of course, a chance collision can never be completely ruled out. The asteroid belt certainly bears no resemblance to the densely populated asteroid fields depicted in fantasies like “Star Wars” and its ilk.

Standing on any asteroid in the belt, you would probably be unable to see other asteroids, due to their distance.

The asteroid belt is located between 2.2 and 3.2 astronomical units (AU) of our sun. One AU is the distance between the Earth and the Sun. The width of the asteroid belt is therefore about 1 AU, or 92 million miles (150 million km).

Its thickness is also about 1 AU thick.

A slightly oblong and rounded rocky body with lots of craters on it.
Here is asteroid 4 Vesta – discovered in 1807 – the 2nd largest asteroid after Ceres. The Dawn spacecraft orbiting Vesta from July 2011 to September 2012. A towering mountain at the south pole of this asteroid – more than twice the height of Mount Everest – is visible at the bottom of the image. All three craters known as the “snowman” are visible at the top left. Image via NASA.

The asteroid belt is often referred to as the “main” belt to distinguish it from other smaller groups of asteroids in the solar system such as the Lagrangians (eg, the Trojan asteroids orbiting the sun of Jupiter) and the Centaurs in the Sun. outside. solar system.

What used to be a homogeneous belt is now known to be slightly more complicated. There are different and distinct areas within the main asteroid belt, particularly on its peripheries, where astronomers now recognize the Hungaria group on the inner edge and the Cybele asteroids on the outside. Towards the middle of the belt is the very inclined Phocée family.

In addition, astronomers have established that the age of the asteroids in the main belt also varies. They have now classified several groups of asteroids based on their age, including the Karin family, a group of around 90 main belt asteroids that share an orbit and are believed to have originated from a single object around 5 years ago, 7 million years old. And there’s the Veritas family, from about 8.3 million years ago. A very recent group is the Datura family, dating only 530,000 years ago from a collision.

Read Wikipedia on asteroid families.

Read on Wikipedia about asteroids that have been visited by spacecraft

A very oblong rocky asteroid.
To be round, a body in space must have an internal mass sufficient to have a gravity strong enough to have taken the shape of a ball. Most asteroids fail to do this and therefore come in all kinds of shapes. Here is the asteroid 433 Eros – discovered in 1898 – now famous as the 1st asteroid ever to orbit by a spacecraft, NEAR Shoemaker, in 1998. This object is considered a main belt asteroid: although its orbit intersects with that of Mars, it does not quite reach that of Earth. Yet it is also considered a near-Earth asteroid… a topic for another day! Image via NASA.

Conclusion: The asteroid belt is a region of our solar system – between the orbits of Mars and Jupiter – in which many small bodies orbit our sun.

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