Description of asteroids. Asteroids - space wanderers of the solar system

Asteroids, or small planets, are much smaller in size than such solar system bodies as Earth, Venus and even Mercury. However, they cannot but be considered full-fledged “residents” of our piece of the Galaxy.

Main belt

The asteroids of the solar system are concentrated in several zones. The most impressive part of them is located between the orbits of Mars and Jupiter. This cluster of small bodies was called the Main Cluster. The mass of all objects located here is negligible by cosmic standards: it makes up only 4% of the lunar mass. Moreover, the largest asteroids make a decisive contribution to this parameter. Both their movement and the movement of their smaller counterparts, as well as parameters such as composition, shape and origin, attracted the attention of astronomers at the beginning of the 19th century: Ceres, previously considered the largest asteroid, and now classified as a dwarf planet, was discovered the first of January 1801.

Beyond Neptune

The Kuiper belt, the Orth cloud and the scattered disk began to be considered and studied as places of accumulation of a large number of small ones a little later. The first of these is located beyond the orbit of Neptune. It was opened only in 1992. According to researchers, the Kuiper belt is much longer and more massive than a similar formation between Mars and Jupiter. Small bodies located here differ from the objects of the Main Belt in composition: methane, ammonia and water here prevail over solid rocks and metals characteristic of the “inhabitants” of the Asteroid Belt.

The existence of the Orth cloud has not been proven today, but it corresponds to many theories describing the Solar system. Presumably the Orta cloud, which is a spherical region, is located beyond the orbits of the planets, at a distance of approximately from the Sun. Space objects consisting of ammonia, methane and water ice are located here.

The scattered disk region overlaps somewhat with the Kuiper Belt. Scientists do not yet know its origin. Objects consisting of different types ice.

Comparing a comet with an asteroid

To accurately understand the essence of the issue, it is necessary to distinguish between two astronomical concepts: “comet” and “asteroid”. Until 2006, there was no certainty regarding the differences between these objects. On general assembly In the named year, the IAS assigned specific characteristics to the comet and asteroid, allowing each to be more or less confidently assigned to a specific category.

A comet is an object moving in a very elongated orbit. When approaching the Sun as a result of sublimation of ice located near the surface, the comet forms a coma - a cloud of dust and gas that grows as the distance between the object and the star decreases and is often accompanied by the formation of a “tail.”

Asteroids do not form comas and, as a rule, have less elongated orbits. Those of them that move along trajectories similar to those of comets are considered the nuclei of so-called extinct comets (an extinct or degenerate comet is an object that has lost everything volatiles and not forming therefore whom).

The largest asteroids and their movement

There are very few truly large objects by cosmic standards in the Main Asteroid Belt. Most of the mass of all bodies located between Jupiter and Mars falls on four objects - Ceres, Vesta, Pallas and Hygiea. The first was considered the largest asteroid until 2006, then it was given the status of Ceres - an almost round body with a diameter of about 1000 km. Its mass is approximately 32% of the total mass of all famous objects belts

The most massive object after Ceres is Vesta. In size of asteroids, only Pallas is ahead of it (after the recognition of Ceres dwarf planet). Pallas is also distinguished from the rest by an unusually strong axis tilt.

Hygiea is the fourth largest object in the Main Belt in terms of size and mass. Despite its size, it was discovered much later than several smaller asteroids. This is due to the fact that Hygiea is a very dim object.

All named bodies rotate around the Sun in the same direction as the planets and do not cross the Earth.

Features of orbits

The largest asteroids and their movement obey the same laws as the movements of other similar bodies in the belt. Their orbits are constantly influenced by the planets, especially the giant Jupiter.

All asteroids rotate in slightly eccentric orbits. The movement of asteroids exposed to Jupiter takes place in slightly shifting orbits. These displacements can be described as oscillations around some average position. The asteroid spends up to several hundred years on each such oscillation, so observational data today are not enough to clarify and test theoretical constructions. However, in general, the hypothesis of changing orbits is generally accepted.

The result of shifting orbits is an increased possibility of collisions. In 2011, evidence was obtained to suggest that Ceres and Vesta may collide in the future.

The largest asteroids and their movements are constantly under the close attention of scientists. Features of changes in their orbits and other characteristics shed light on some cosmic patterns, which, in the process of data analysis, are often extrapolated to objects larger than asteroids. The movement of asteroids is also studied with the help of spacecraft, which temporarily become satellites of certain objects. One of them entered the orbit of Ceres on March 6, 2015.

Any cosmic body with a diameter of more than 3 kilometers threatens the Earth with the disappearance of civilization in the event of a collision. Therefore, it is so important to know about the largest asteroids and their movement in orbits, because among the 670 thousand objects of the solar system there are very unusual specimens. The bulk of large celestial bodies are located in the so-called asteroid belt, far from Earth, so there is no direct threat to us. As they were discovered, they were called female names from Roman and Greek mythology, and then, with the increase in the number of discoveries, this rule was no longer observed.

Ceres

This rather large celestial body (diameter 975 * 909 km) has been many things since its discovery: both a full-fledged planet of the solar system and an asteroid, and since 2006 it has acquired new status- dwarf planet. The last name is the most correct, since Ceres is not the main one in its orbit, but only the largest in the asteroid belt. It was discovered quite by accident by the Italian astronomer Piazzi in 1801.

Ceres has a spherical shape (unusual for asteroids) with a rocky core and a crust of water ice and minerals. The distance between the closest point in the orbit of this solar satellite and the Earth is 263 million kilometers. Its path lies between Mars and Jupiter, but there is some tendency towards chaotic movement (which increases the chances of collisions with other asteroids and a change in orbit). It is not visible to the naked eye from the surface of our planet - it is only a 7th magnitude star.

Pallas

The size is 582 * 556 kilometers, and it is also part of the asteroid belt. The angle of Pallas' rotation axis is very high - 34 degrees (for other celestial bodies it does not exceed 10). Pallas moves in an orbit with a large degree of deviation, which is why its distance to the Sun changes all the time. This is a carbon asteroid, rich in silicon and is of interest in the future from the point of view of mining.

Vesta

This is the heaviest asteroid to date, although it is smaller in size than the previous ones. Due to the composition of the rock, Vesta reflects 4 times more light than Ceres, although its diameter is half that. It turns out that this is the only asteroid whose movement can be observed with the naked eye from the surface of the Earth when it approaches once every 3-4 years to a minimum distance of 177 million kilometers. Its movement is carried out along the inner part of the asteroid belt and never crosses our orbit.

Interestingly, with a length of 576 kilometers, there is a crater with a diameter of 460 kilometers on its surface. In general, the entire asteroid belt around Jupiter is a giant quarry, where celestial bodies collide with each other, fly into pieces and change their orbits - but how did Vesta survive a collision with such large object and retained its integrity remains a mystery. Its core is made of heavy metal, and the crust is made of light rocks.

Hygeia

This asteroid does not intersect with our orbit and revolves around the Sun. A very dim celestial body, although it has a diameter of 407 kilometers, was discovered later than the others. This is the most common type of asteroid, with a carbonaceous content. Typically, observing Hygia requires a telescope, but at its closest approach to Earth, it can be seen with binoculars.

Today, an asteroid falling to Earth will bring with it casualties, destruction and cataclysms. But, despite the fact that astronomers call this type of celestial bodies “space debris,” we owe the emergence of life on our planet to them. In 2010, independently of each other, two groups of researchers discovered on the Themis asteroid (one of the 20 largest) water ice, complex hydrocarbons and molecules, the isotopic composition of which coincides with that of Earth.

Asteroids are celestial bodies that were formed by mutual attraction dense gas and dust orbiting our Sun early in its formation. Some of these objects, like an asteroid, have reached enough mass to form a molten core. At the moment Jupiter reached its mass, most of the planetesimals (future protoplanets) were split and ejected from the original asteroid belt between Mars and. During this era, some asteroids were formed due to the collision of massive bodies within the influence of Jupiter's gravitational field.

Orbit classification

Asteroids are classified by features such as visible reflections sunlight and characteristics of the orbits.

According to the characteristics of their orbits, asteroids are grouped into groups, among which families can be distinguished. A group of asteroids is considered to be a number of such bodies whose orbital characteristics are similar, that is: semi-axis, eccentricity and orbital inclination. An asteroid family should be considered a group of asteroids that not only move in close orbits, but are probably fragments of one big body, and formed as a result of its split.

The largest of famous families may number several hundred asteroids, the most compact ones being within ten. Approximately 34% of asteroid bodies are members of asteroid families.

As a result of the formation of most groups of asteroids in the Solar System, their parent body was destroyed, but there are also groups whose parent body survived (for example).

Classification by spectrum

Spectral classification is based on spectrum electromagnetic radiation, which is the result of the asteroid reflecting sunlight. Registration and processing of this spectrum makes it possible to study the composition of a celestial body and assign an asteroid to one of the following classes:

• A group of carbon asteroids or C-group. Representatives of this group consist mostly of carbon, as well as elements that were part of the protoplanetary disk of our solar system in the early stages of its formation. Hydrogen and helium, as well as other volatile elements, are practically absent in carbonaceous asteroids, however, the presence of various minerals is possible. Another distinctive feature Such bodies have a low albedo - reflectivity, which requires the use of more powerful observation tools than in the study of asteroids of other groups. More than 75% of asteroids in the Solar System are representatives of the C-group. The most famous bodies of this group are Hygeia, Pallas, and once - Ceres.
• A group of silicon asteroids or S-group. These types of asteroids are composed primarily of iron, magnesium and some other rocky minerals. For this reason, silicon asteroids are also called rocky asteroids. Such bodies have a fairly high albedo, which makes it possible to observe some of them (for example, Iris) simply with the help of binoculars. The number of silicon asteroids in the solar system is 17% of total number, and they are most common at a distance of up to 3 astronomical units from the Sun. Largest representatives S-groups: Juno, Amphitrite and Herculina.

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 the asteroids is also confirmed by the fact that their brightness decreases quite rapidly with increasing phase angle. Due to the large distance from the Earth and their small size, it is rather problematic to obtain more accurate data on asteroids. The force of gravity on an asteroid is so small that it is not able to give them a spherical shape 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 have avoided collisions with medium-sized bodies can retain the spherical shape acquired during the formation of the planets.