What is a meteor? Meteors: photo. Asteroids, comets, meteors, meteorites

Asteroids, comets, meteors, meteorites are astronomical objects that seem to be the same for the uninitiated in the basics of the science of celestial bodies. In fact, they differ in several parameters. Properties that characterize asteroids, comets, meteors, meteorites, remember fairly simply. They also have a certain similarity: similar objects are classified as small bodies, often classified as space debris. About what a meteor is, how it differs from an asteroid or a comet, what are their properties and origin, and will be discussed below.

Tailed Wanderers

Comets are cosmic objects, consisting of frozen gases and stone. They are born in remote areas of the solar system. Modern scientists suggest that the main sources of comets are the Kuiper belt connected with each other and the scattered disk, as well as the hypothetically existing Oort cloud.

Comets have highly elongated orbits. When approaching the Sun, they form a tail to someone. These elements consist of evaporating gaseous substances (water vapor, ammonia, methane), dust and stones. The head of a comet, or coma, is a shell of the smallest particles, distinguished by brightness and visibility. It has a spherical shape and reaches a maximum size when approaching the Sun at a distance of 1.5-2 astronomical units.

In the front of the coma is the nucleus of the comet. As a rule, it has a relatively small size and elongated shape. With a significant distance from the Sun, the nucleus is all that remains of the comet. It consists of frozen gases and rocks.

Types of comets

The classification of these cosmic bodies is based on the periodicity of their circulation around the luminary. Comets flying around the Sun in less than 200 years are called short-period ones. Most often they fall into the inner regions of our planetary system from the Kuiper belt or the scattered disk. Long-period comets are treated with a period of more than 200 years. Their "homeland" is the Oort cloud.

"Minor planets"

Asteroids consist of hard rocks. By their size, they are much inferior to the planets, although some representatives of these space objects have satellites. Most of the small planets, as they were called earlier, are concentrated in the Main Asteroid Belt, located between the orbits of Mars and Jupiter.

The total number of such cosmic bodies, known for 2015, exceeded 670 thousand. Despite such an impressive number, the contribution of asteroids to the mass of all objects of the solar system is insignificant - only 3-3.6 * 10 ²¹ kg. This is only 4% of the analogous parameter of the Moon.

Not all bodies of a small size belong to asteroids. The criterion of selection is the diameter. If it exceeds 30 m, then the object is referred to asteroids. The bodies with smaller dimensions were called meteoroids.

Classification of asteroids

At the heart of the grouping of these cosmic bodies are several parameters. Asteroids are united by the characteristics of their orbits and the spectrum of visible light, which was reflected from their surface.

By the second criterion, three main classes are distinguished:

• Carbon (C);
• Silicate (S);
• Metal (M).

The first category includes about 75% of all known today asteroids. As the equipment improves and more detailed research of such objects, the classification expands.

Meteoroids

A meteoroid is another type of cosmic body. These are not asteroids, comets, meteors or meteorites. The peculiarity of these objects is their small size. Meteoroids in their dimensions are located between asteroids and cosmic dust. Thus, they include bodies with a diameter less than 30 m. Some scientists define a meteoroid as a solid with a diameter of 100 μm to 10 m. In their origin they are primary or secondary, that is, formed after the destruction of larger objects.

When entering the Earth's atmosphere, the meteoroid begins to glow. And here we are already approaching the answer to the question what is a meteor.

Falling star

Sometimes among the shimmering luminaries in the night sky one suddenly flashes up, describes a small arc and disappears. Who at least once saw this, he knows what a meteor is. These are "falling stars," which have no relation to real stars. Meteor is actually an atmospheric phenomenon that occurs when small objects (those meteoroids) get into the air envelope of our planet. The observed brightness of the flash depends directly on the initial dimensions of the cosmic body. If the meteor shine exceeds the fifth magnitude, it is called a bolide.

Observation

Such phenomena can be admired only from planets with an atmosphere. Meteors on the Moon or on Mercury can not be observed, since they do not have an air envelope.

Under suitable conditions, "falling stars" can be seen every night. It is best to enjoy meteors in good weather and at a considerable distance from a more or less powerful source of artificial lighting. Also in the sky there should be no moon. In this case, up to 5 meteors per hour can be seen with the naked eye. The objects that lead to the appearance of such single "falling stars" revolve around the sun in very different orbits. Therefore, the place and time of their appearance in the sky can not be accurately predicted.

Streams

Meteors, photos of which are also presented in the article, as a rule, have a somewhat different origin. They are part of one of several swarms of small cosmic bodies orbiting a certain trajectory around the star. In their case, the ideal period for observation (the time when, looking at the sky, anyone can quickly understand what a meteor is) is pretty well defined.

A swarm of similar cosmic objects is also called a meteor shower. Most often they are formed when the nucleus of the comet is destroyed. Individual swarm particles move parallel to each other. However, from the surface of the Earth it seems that they fly out of a certain small area of the sky. This area is called the stream radiant. The name of a meteoric swarm, as a rule, is given by a constellation in which its visual center (radiant) is located, or by the name of a comet, the decay of which led to its appearance.

Meteors, photos of which can be easily obtained with special equipment, refer to such large streams as Perseids, Quadrantids, eta- Aquarids, Lyrids, Geminids. In total, the existence of 64 streams is recognized today and about 300 are awaiting confirmation.

Heavenly Stones

Meteorites, asteroids, meteors and comets are related concepts to one or other of the criteria. The first represent the space objects that fell to Earth. Most often their source is asteroids, less often - comets. Meteorites carry invaluable data about the various corners of the solar system outside the Earth.

Most of these bodies, which hit our planet, are very small. The most impressive in their dimensions, meteorites leave traces after the impact, which are quite noticeable even after millions of years. Well known is the crater near the town of Winslow in Arizona. The fall of the meteorite in 1908 presumably became the cause of the Tunguska phenomenon.

Such large objects "visit" the Earth every few million years. Most of the meteorites found are rather modest in size, but they do not become less valuable for science.

According to scientists, such objects can tell a lot about the time of the formation of the solar system. Presumably, they carry particles of matter, from which young planets were composed. Some meteorites come to us from Mars or the Moon. Such space wanderers allow you to learn something new about neighboring objects without huge costs for distant expeditions.

To remember the differences of the objects described in the article, one can describe the transformation of such bodies in space multiple times. An asteroid consisting of solid rock rocks, or a comet that is an ice block, in the process of destruction, give birth to meteoroids that, when entering the atmosphere of the planet, flash with meteors, burn in it or fall, turning into meteorites. The latter enrich our knowledge of all the previous ones.

Meteorites, comets, meteors, as well as asteroids and meteoroids - participants in the continuous space movement. The study of these objects brings a great contribution to our understanding of the structure of the universe. As the equipment improves, astrophysicists receive more and more data about such objects. A recently completed mission of the Rosetta probe clearly demonstrated how much information can be obtained by a detailed study of such cosmic bodies.