Description of asteroids. Asteroid – Magazine "All about Space" How much does an asteroid weigh

An asteroid is a relatively small, rocky cosmic body similar to a planet in the solar system. Many asteroids orbit the Sun, and the largest cluster of them is located between the orbits of Mars and Jupiter and is called the asteroid belt. The largest known asteroid, Ceres, is also located here. Its dimensions are 970x940 km, i.e. almost round in shape. But there are also those whose sizes are comparable to dust particles. Asteroids, like comets, are remnants of the substance from which our solar system was formed billions of years ago.

Scientists suggest that more than half a million asteroids with a diameter greater than 1.5 kilometers can be found in our galaxy. Recent research has shown that meteorites and asteroids have similar compositions, so asteroids may well be the bodies from which meteorites are formed.

Asteroid exploration

The study of asteroids dates back to 1781, after William Herschel discovered the planet Uranus to the world. At the end of the 18th century, F. Xaver gathered a group of famous astronomers who searched for the planet. According to calculations, Xavera should have been located between the orbits of Mars and Jupiter. At first the search did not produce any results, but in 1801, the first asteroid was discovered - Ceres. But its discoverer was the Italian astronomer Piazzi, who was not even part of Xaver’s group. Over the next few years, three more asteroids were discovered: Pallas, Vesta and Juno, and then the search stopped. Only 30 years later, Karl Louis Henke, who showed interest in studying the starry sky, resumed their search. Since this period, astronomers have discovered at least one asteroid per year.

Characteristics of asteroids

Asteroids are classified according to the spectrum of reflected sunlight: 75% of them are very dark carbonaceous class C asteroids, 15% are grayish-siliceous class S asteroids, and the remaining 10% include metallic class M and several other rare species.

The irregular shape of asteroids is also confirmed by the fact that their brightness decreases quite quickly with increasing phase angle. Due to their large distance from the Earth and their small size, it is quite problematic to obtain more accurate data about asteroids. The force of gravity on an asteroid is so small that it is not able to give them the spherical shape that is characteristic of all planets. This gravity allows broken asteroids to exist as separate blocks that are held close to each other without touching. Therefore, only large asteroids that avoided collisions with medium-sized bodies can retain the spherical shape acquired during the formation of planets.

A small body in the solar system that moves in orbit around the sun is called an asteroid. Asteroids are significantly smaller than planets in size and do not have their own atmosphere, although, like planets, they can have their own satellites. Asteroids are made of rocks and metals, mainly nickel and iron.


Term "asteroid" translated from Greek means "star-like" . This name was coined by William Herschel, who noticed that through a telescope lens asteroids look like small points of stars. Planets are visible through a telescope as disks.

Until 2006, a synonym for the term “asteroid” was “minor planet”. Asteroids differ from meteoroids in size: the diameter of an asteroid must be at least thirty meters.

Sizes and motion of asteroids

The largest asteroids known today are (4) Vesta and (2) Pallas, with a diameter of about 500 kilometers. Vesta can be seen from Earth with the naked eye. The third large asteroid, Ceres, was reclassified as a dwarf planet in 2006. The dimensions of Ceres are about 909 by 975 kilometers.

According to scientists, there are between a million and two million asteroids larger than a kilometer in diameter in the solar system.


Most of these celestial bodies are located in the belt between Jupiter and Mars, but individual asteroids can move in an elliptical orbit outside this belt, around the Sun. There is another well-known asteroid belt, not far from the orbits of Pluto and Neptune - the Coyer Belt.

Asteroids, as already mentioned, do not stand still; in the process of movement they can collide with each other and satellites. On the surface of planets and satellites that asteroids collided with, deep marks - craters - remain. The diameter of the crater can reach several kilometers. During a collision, relatively small fragments - meteorites - can break off from asteroids.

Origin and features

Scientists have been trying for a very long time to find an answer to the question - where do asteroids come from? Today, two versions are popular. According to one of them, asteroids are the remnants of matter from which, in fact, all the planets of the solar system were formed. Another theory suggests that asteroids are fragments of large planets that previously existed and were destroyed due to an explosion or collision.


Asteroids are cold cosmic bodies. These are, in fact, huge stones that do not emit heat or reflect it from the Sun, since they are very far from it. Even an asteroid located close to the star, having heated up, will give off this heat almost immediately.

What are the names of asteroids?

The first asteroids discovered were named after ancient Greek mythological heroes and gods. By a strange coincidence, at first these were female names, but only an asteroid with an unusual orbit could count on a male name. Later, this trend gradually faded away.

In addition, the right to give asteroids any names was given to people who discovered them for the first time. Thus, today, whoever discovers a new asteroid can name it according to his own taste, and even call it by his own name.

But there are certain rules for naming asteroids. They can be given names only after the orbit of the celestial body has been reliably calculated, and until that time the asteroid is given a non-permanent name. The asteroid's designation reflects the date it was discovered.

For example, 1975DC, where the numbers indicate the year, the letter D is the number of the crescent in the year when the asteroid was discovered, and C is the serial number of the celestial body in this crescent (the asteroid given in the example was the third to be discovered). There are 24 crescents in total, and there are 26 letters in the English alphabet, so they decided not to use two letters - I and Z - when naming asteroids.


If more than 24 asteroids are discovered in one crescent, the second letter is assigned an index of 2, the venture - 3, and so on. And after the asteroid receives an official name (and it happens that this takes more than one decade - all this time the orbit is being calculated), its name includes the serial number and the name itself.

Scientists believe that there are several hundred thousand asteroids in this belt, and there may be millions of them in total in outer space.

Asteroid sizes range from 6 m to 1000 km in diameter. (Although 6 m seems like quite a bit compared to 1000 km, even a small asteroid would cause a strong effect if it fell by .)

Small changes in orbits sometimes cause asteroids to collide with each other, causing small pieces to break off.

It happens that these small fragments leave their orbits and burn up into the Earth, and then they are called .

Asteroids: "like stars"

This is exactly how the name of these celestial bodies is translated from Greek, although they have nothing in common with asteroids.

Thus, the asteroid belt is not the remnants of a planet, but a planet that never “managed” to form due to the influence of Jupiter and other giant planets.

Threat from orbit

A huge number of asteroids and large meteoroids move around the Solar System.

Most of them are concentrated between the orbits of Mars and Jupiter, but from time to time some of these space objects change their usual orbits due to collisions or gravitational disturbances and end up near the Earth.

This happens less often with comets, but asteroids pose a real danger, so astronomers closely monitor their movements.

In the past, the Earth has had to endure collisions with asteroids of various sizes more than once. Researchers believe that the result of such events was formation and death.

A small asteroid with a diameter of 20-30 m, moving at a speed of 20 km/s, when falling to Earth, releases as much energy as a nuclear charge with a capacity of a megaton in TNT equivalent.

Asteroids of this size can cause colossal damage, but do not threaten the planet with a global catastrophe. Therefore, the attention of “celestial patrols” is focused on small celestial bodies whose dimensions exceed half a kilometer.

One of them is the asteroid Apophis, discovered in 2004, whose orbit will approach the Earth in 2029 at a distance of 29 thousand km.

At the same time, there is approximately one chance in a hundred that an asteroid could collide with our planet, so now all movements of Apophis in orbit are carefully monitored and plans are being developed for its destruction if the probability of a collision becomes really high.

The fall of a cosmic body like Apophis to Earth can lead to the complete destruction of villages within a radius of 300 km, giant ones at sea and unpredictable environmental changes.

Asteroids in the Kuiper Belt

Since 1992, astronomers began to discover more and more asteroids in the Kuiper belt - today more than a thousand of them are known. They differ in composition from those that form the belt between Mars and Jupiter.

In the main asteroid belt, three groups of bodies are distinguished: silicate (stony), metallic and carbonaceous. Kuiper belt asteroids consist almost entirely of debris.

Modern telescopes do not give an idea of ​​​​the appearance of asteroids, and close acquaintance with them began only when they began to approach small planets. Most of the asteroids turned out to be irregularly shaped bodies covered with meteorites.

Researchers identify “families” among asteroids—groups of small asteroids with similar orbits, formed when larger asteroids collide with other objects. Three of them often approach the Earth’s orbit - these are the family of Amur, Apollo and Aten.

Asteroids? First of all, I would like to say that this is the name given to rocky solid bodies that move in elliptical orbits around the Sun, like planets. However, space asteroids are much smaller in size than the planets themselves. Their diameter is approximately within the following limits: from several tens of meters to a thousand kilometers.

When wondering what asteroids are, a person involuntarily thinks about where this term even came from and what it means. It is translated as “star-like,” and was introduced in the 18th century by an astronomer named William Herschel.

Comets and asteroids can be seen as point sources of a certain light, more or less bright. Although in the visible range, data does not emit anything - it only reflects the sunlight that falls on it. It should be noted that comets are different from asteroids. The first is their different appearance. The comet is easily recognized by its brightly glowing core and the tail that extends from it.

Most of the asteroids that are known to astronomers today move between the orbits of Jupiter and Mars at a distance of approximately 2.2-3.2 AU. e. (that is, from the Sun. To date, scientists have discovered about 20 thousand asteroids. Only fifty percent of them are registered. What are registered asteroids? These are celestial bodies that have been assigned numbers, and sometimes even proper names. Their orbits have been calculated with very great accuracy. It should be noted that these celestial bodies usually have the names that were assigned to them by their discoverers. The names for asteroids are taken, as a rule, from ancient Greek mythology.

In general, from the above definition it becomes clear what asteroids are. However, what else is characteristic of them?

As a result of observations of these celestial bodies through a telescope, an interesting fact was discovered. The brightness of a large number of asteroids can change, and in a very short time - this takes several days, or even several hours. Scientists have long hypothesized that these changes in the brightness of asteroids are associated with their rotation. It should be noted that they are determined, first of all, by their irregular forms. And the first photographs that captured these celestial bodies (the photographs were taken with the help of this theory) confirmed this theory, and also showed the following: the surfaces of the asteroids are completely pitted with deep craters and craters of various sizes.

The largest asteroid discovered in our solar system was previously considered to be the celestial body Ceres, whose dimensions were about 975 x 909 kilometers. But since 2006 it received a different status. And it began to be called And the other two large asteroids (called Pallas and Vesta) have a diameter of 500 kilometers! Another interesting fact should also be noted. The fact is that Vesta is the only asteroid that can actually be observed with the naked eye.