Solar system objects comets asteroids. Comets of the solar system. facts you need to know about comets

Moving in orbit around the Sun. The comet got its name from the Greek word for “long-haired,” because people in Ancient Greece They believed that comets were like stars with flowing hair.

Comets form tail, only when they are located close to the Sun. When are they far from Sun, then comets are dark, cold, icy objects.

The icy body of a comet is designated as core. It occupies up to 90% of the comet's weight. The core is formed from all sorts of ice, dirt and dust that formed the foundation of the solar system approximately 4.6 billion years ago. At the same time, the ice consists of frozen water and a mixture of various gases, such as ammonia, carbon, methane, etc. And in the center there is a fairly small core of stone.

As the ice approaches the Sun, it begins to heat up and evaporate, releasing gases and grains of dust that form a cloud or atmosphere around the comet called coma. As the comet continues to move closer to the Sun, dust particles and other debris in the coma are blown away due to the pressure of sunlight from the Sun. This explains the fact that comet tails are always directed away from the Sun. This process forms dust tail(it can be observed even with the naked eye). Most often, comets also have a second tail. Plasma tail clearly visible in photographs, but very difficult to see without a telescope.

Over time, comets begin to move in the opposite direction from the Sun, and their activity decreases, and their tails and comas disappear. They become an ordinary ice core again. And when comet orbits will again lead them to the Sun, then the head and tails of the comet will appear again.

The dimensions of comets are very, very different. The smallest comets have a core size of up to 16 kilometers. The largest core recorded was approximately 40 kilometers in diameter. Tails of dust And ions can be colossal. Ionic tail Comet Hyakutake stretches approximately 580 million kilometers.

There are many hypotheses for the origin of comets, but the most popular is that comets were born from the remains of substances at birth solar system. Some scientists are confident that it was comets that brought water and organic substances to Earth, which later became the primary source of life.

Meteor Rain It will be possible to see when the Earth's orbit intersects the trail of debris left behind by the comet. From Earth every year in August you can see Perseids (meteor shower). It happens during the time when the Earth passes through orbit of Comet Swift-Tuttle.

Astronomers do not know the exact number of comets, this is explained by the fact that the vast majority of them have never been seen. As of 2010, just over 4,000 comets were recorded in our Solar System.

Comets can change their flight direction, which is explained by several factors: when passing near a planet, the latter can insignificantly change comet path; also comets moving towards the Sun fall directly into it.

Over millions of years, most comets leave gravitationally the boundaries of the solar system or lose their ice and disintegrate during movement.

Comet(from ancient Greek. κομ?της , kom?t?s - “hairy, shaggy”) - small ice heavenly body, orbiting in the Solar System, which partially evaporates as it approaches the Sun, resulting in a diffuse shell of dust and gas, as well as one or more tails.
The first appearance of a comet, which was recorded in the chronicles, dates back to 2296 BC. And this was done by a woman, the wife of Emperor Yao, who gave birth to a son who later became Emperor Ta-Yu, the founder of the Khia dynasty. It was from this moment that Chinese astronomers monitored the night sky and only thanks to them, we know about this date. The history of cometary astronomy begins with it. The Chinese not only described comets, but also plotted the paths of comets on a star map, which allowed modern astronomers to identify the brightest of them, trace the evolution of their orbits, and obtain other useful information.
It is impossible not to notice such a rare spectacle in the sky when a foggy body is visible in the sky, sometimes so bright that it can sparkle through the clouds (1577), eclipsing even the Moon. Aristotle in the 4th century BC explained the phenomenon of a comet as follows: light, warm, “dry pneuma” (gases of the Earth) rises to the boundaries of the atmosphere, falls into the sphere of heavenly fire and ignites - this is how “tailed stars” are formed. Aristotle argued that comets cause severe storms and drought. His ideas have been generally accepted for two thousand years. In the Middle Ages, comets were considered harbingers of wars and epidemics. Thus, the Norman invasion of Southern England in 1066 was associated with the appearance of Halley's comet in the sky. The fall of Constantinople in 1456 was also associated with the appearance of a comet in the sky. While studying the appearance of a comet in 1577, Tycho Brahe determined that it was moving far beyond the orbit of the Moon. The time to study the orbits of comets had begun...
The first fanatic eager to discover comets was an employee of the Paris Observatory, Charles Messier. He entered the history of astronomy as the compiler of a catalog of nebulae and star clusters, intended to search for comets, so as not to mistake distant nebulous objects for new comets. Over 39 years of observations, Messier discovered 13 new comets! In the first half XIX century Among the “catchers” of comets, Jean Pons especially distinguished himself. The caretaker of the Marseille Observatory, and later its director, built a small amateur telescope and, following the example of his compatriot Messier, began searching for comets. The matter turned out to be so fascinating that in 26 years he discovered 33 new comets! It is no coincidence that astronomers nicknamed it the “Comet Magnet.” The record set by Pons remains unsurpassed to this day. About 50 comets are available for observation. In 1861, the first photograph of a comet was taken. However, according to archival data, a record dated September 28, 1858 was discovered in the annals of Harvard University, in which Georg Bond reported an attempt to obtain a photographic image of the comet at the focus of a 15" refractor! At a shutter speed of 6", the brightest part of the coma measuring 15 arc seconds was worked out. The photograph has not been preserved.
The 1999 Comet Orbit Catalog contains 1,722 orbits for 1,688 cometary appearances from 1,036 different comets. From ancient times to the present day, about 2000 comets have been noticed and described. In the 300 years since Newton, the orbits of more than 700 of them have been calculated. The general results are as follows. Most comets move in ellipses, moderately or strongly elongated. Comet Encke takes the shortest route - from the orbit of Mercury to Jupiter and back in 3.3 years. The most distant of those observed twice is a comet discovered in 1788 by Caroline Herschel and returning 154 years later from a distance of 57 AU. In 1914, Delavan's Comet set the distance record. It will move away to 170,000 AU. and “finishes” after 24 million years.
On this moment More than 400 short-period comets have been discovered. Of these, about 200 were observed during more than one perihelion passage. Many of them belong to so-called families. For example, approximately 50 of the shortest-period comets (their complete revolution around the Sun lasts 3-10 years) form the Jupiter family. Slightly smaller in number are the families of Saturn, Uranus and Neptune (the latter, in particular, includes the famous Comet Halley).
Terrestrial observations of many comets and the results of studies of Halley's comet using spacecraft in 1986 they confirmed the hypothesis first expressed by F. Whipple in 1949 that comet nuclei are something like “dirty snowballs” several kilometers across. They appear to consist of frozen water, carbon dioxide, methane and ammonia with dust and rocky matter frozen inside. As the comet approaches the Sun, the ice begins to evaporate under the influence of solar heat, and the escaping gas forms a diffuse luminous sphere around the nucleus, called a coma. The coma can be up to a million kilometers across. The nucleus itself is too small to be seen directly. Observations in the ultraviolet range of the spectrum carried out from spacecraft have shown that comets are surrounded by huge clouds of hydrogen, many millions of kilometers in size. Hydrogen is produced by the decomposition of water molecules under the influence of solar radiation. In 1996, X-ray emission from comet Hyakutake was discovered, and subsequently it was discovered that other comets are sources of X-ray radiation.
Observations in 2001, carried out using the Subara telescope's high-dispersive spectrometer, allowed astronomers to measure for the first time the temperature of frozen ammonia in the comet's nucleus. Temperature value at 28 + 2 degrees Kelvin suggests that Comet LINEAR (C/1999 S4) formed between the orbits of Saturn and Uranus. This means that astronomers can now not only determine the conditions under which comets form, but also find where they originate. Using spectral analysis, organic molecules and particles were discovered in the heads and tails of comets: atomic and molecular carbon, carbon hybrid, carbon monoxide, carbon sulfide, methyl cyanide; inorganic components: hydrogen, oxygen, sodium, calcium, chromium, cobalt, manganese, iron, nickel, copper, vanadium. The molecules and atoms observed in comets, in most cases, are “fragments” of more complex parent molecules and molecular complexes. The nature of the origin of parent molecules in cometary nuclei has not yet been solved. So far it is only clear that these are very complex molecules and compounds such as amino acids! Some researchers believe that this chemical composition can serve as a catalyst for the emergence of life or the initial condition for its origin when these complex compounds enter the atmosphere or surface of planets with sufficiently stable and favorable conditions.