Asteroids, comets, meteors, meteorites - astronomical objects that seem the same to the uninitiated in the basics of the science of celestial bodies. In fact, they differ in several ways. The properties that characterize asteroids, comets, meteors, meteorites are quite easy to remember. They also have a certain similarity: such 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 space objects consisting of frozen gases and stone. They originate in remote areas of the solar system. Modern scientists suggest that the main sources of comets are the interconnected Kuiper belt and scattered disk, as well as the hypothetically existing Oort cloud.
Comets have strongly elongatedorbits. As they approach the Sun, they form a coma and a tail. 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 tiny particles, distinguished by brightness and visibility. It has a spherical shape and reaches its maximum size when approaching the Sun at a distance of 1.5-2 astronomical units.
In front of the coma is the nucleus of a comet. It, as a rule, has a relatively small size and an elongated shape. At a considerable 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 star. Comets that fly around the Sun in less than 200 years are called short-period comets. Most often, they fall into the inner regions of our planetary system from the Kuiper belt or scattered disk. Long-period comets revolve with a period of more than 200 years. Their "homeland" is the Oort cloud.
Minor Planets
Asteroids are made of solid rocks. In size, they are much inferior to the planets, although some representatives of these space objects have satellites. Most of the minor planets, as they used to be called, are concentrated in the main asteroid belt, located between the orbits of Mars and Jupiter.
The total number of such cosmic bodies known in 2015 exceeded 670,000. Despite such an impressive number,the contribution of asteroids to the mass of all objects in the solar system is insignificant - only 3-3.61021 kg. This is only 4% of the similar parameter of the Moon.
Not all small bodies are classified as asteroids. The selection criterion is the diameter. If it exceeds 30 m, then the object is classified as an asteroid. Bodies with smaller dimensions are called meteoroids.
Classification of asteroids
The grouping of these cosmic bodies is based on several parameters. Asteroids are grouped according to the features of their orbits and the spectrum of visible light that was reflected from their surface.
According to the second criterion, there are three main classes:
- carbon (C);
- silicate (S);
- metal (M).
Approximately 75% of all asteroids known today belong to the first category. With the improvement of equipment and a more detailed study of such objects, the classification expands.
Meteoroids
Meteoroid is another type of space bodies. They 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 of less than 30 m. Some scientists define a meteoroid as a solid body with a diameter of 100 microns to 10 m. By 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. Andhere we are already approaching the answer to the question, what is a meteor.
Shooting Star
Sometimes, among the twinkling stars in the night sky, one suddenly flashes, describes a small arc and disappears. Anyone who has seen this at least once knows what a meteor is. These are "shooting stars" that have nothing to do with real stars. A meteor is actually an atmospheric phenomenon that occurs when small objects (the same meteoroids) enter the air shell of our planet. The observed brightness of the flash directly depends on the initial dimensions of the cosmic body. If the brilliance of a meteor exceeds the fifth magnitude, it is called a fireball.
Observation
Such phenomena can only be admired from planets with an atmosphere. Meteors on the Moon or Mercury cannot be observed because they do not have an air shell.
When conditions are right, shooting stars can be seen every night. It is best to admire meteors in good weather and at a considerable distance from a more or less powerful source of artificial light. Also, there should be no moon in the sky. In this case, it will be possible to notice up to 5 meteors per hour with the naked eye. The objects that give rise to such single "shooting stars" revolve around the Sun in a variety of orbits. Therefore, the place and time of their appearance in the sky cannot be accurately predicted.
Flows
Meteors, photos of which are also presented in the article, as a rule, have a slightly different origin. They areare part of one of several swarms of small cosmic bodies revolving around the star along a certain trajectory. In their case, the ideal period for observing (the time when, by looking at the sky, anyone can quickly understand what a meteor is) is pretty well defined.
A swarm of similar space objects is also called a meteor shower. Most often they are formed during the destruction of the nucleus of a comet. Individual swarm particles move parallel to each other. However, from the surface of the Earth, they seem to be flying out of a certain small area of the sky. This section is called the radiant of the stream. The name of a meteor swarm is usually given by the constellation in which its visual center (radiant) is located, or by the name of the comet, the disintegration of which led to its appearance.
Meteors, photos of which are easy to obtain with special equipment, belong to such large streams as the Perseids, Quadrantids, Eta Aquarids, Lyrids, Geminids. In total, the existence of 64 streams has been recognized to date, and about 300 more are awaiting confirmation.
Heavenly Stones
Meteorites, asteroids, meteors and comets are related concepts according to one or another criteria. The first are space objects that have fallen to Earth. Most often, their source is asteroids, less often - comets. Meteorites carry invaluable data about various parts of the solar system outside the Earth.
Most of these bodies that hit our planet are very small. The most impressive meteorites in their dimensions leave after impacttraces, quite noticeable even after millions of years. Well known is the crater near Winslow, Arizona. A meteorite fall in 1908 allegedly caused the Tunguska phenomenon.
Such large objects "visit" the Earth every few million years. Most of the found meteorites are quite modest in size, but at the same time they do not become less valuable for science.
According to scientists, such objects can tell a lot about the formation of the solar system. Presumably, they carry particles of the substance that young planets were made of. Some meteorites come to us from Mars or the Moon. Such space wanderers allow you to learn something new about nearby objects without huge expenses for distant expeditions.
To memorize the differences between the objects described in the article, we can summarize the transformation of such bodies in space. An asteroid, consisting of solid rock, or a comet, which is an ice block, when destroyed, gives rise to meteoroids, which, when entering the planet's atmosphere, flare up as meteors, burn out 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 are participants in continuous space movement. The study of these objects contributes greatly to our understanding of the structure of the universe. As the equipment improves, astrophysicists receive more and more data on such objects. The relatively recently completed mission of the Rosetta probe is unambiguouslydemonstrated how much information can be obtained from a detailed study of such space bodies.
