Information about the comets of the solar system. What happens in a collision

In 2009, Robert McNaught opened Comet C/2009 R1, which is approaching the Earth, and in mid-June 2010, the inhabitants of the northern hemisphere will be able to see it with the naked eye.

Comet Morehouse(C / 1908 R1) - a comet discovered in the USA in 1908, which was the first of the comets to be actively studied using photography. Amazing changes were seen in the structure of the tail. During the day of September 30, 1908, these changes occurred continuously. On October 1, the tail broke off and could no longer be observed visually, although a photograph taken on October 2 showed three tails. The rupture and subsequent growth of the tails occurred repeatedly.

Comet Tebbutt(C/1861 J1) - A bright comet visible to the naked eye was discovered by an Australian amateur astronomer in 1861. The Earth passed through the comet's tail on June 30, 1861.

Comet Hyakutake(C/1996 B2) is a large comet that reached magnitude zero in March 1996 and produced a tail estimated to be at least 7 degrees long. Its apparent brightness is largely due to its proximity to the Earth - the comet passed from it at a distance of less than 15 million km. The maximum approach to the Sun is 0.23 AU, and its diameter is about 5 km.

Comet Humason(C / 1961 R1) - a giant comet, discovered in 1961. Its tails, despite being so far from the Sun, still extend 5 AU in length, which is an example of unusually high activity.

Comet McNaught(C/2006 P1), also known as the Great Comet of 2007, is a long-period comet discovered on August 7, 2006 by British-Australian astronomer Robert McNaught and has become the brightest comet in the last 40 years. Residents of the northern hemisphere could easily observe it naked eye in January and February 2007. In January 2007 magnitude comet reached -6.0; The comet was visible everywhere in daylight, and the maximum length of the tail was 35 degrees.

Space is fraught with many unexplored mysteries. The eyes of mankind are constantly turned to the Universe. Each sign we receive from space provides answers and at the same time raises many new questions.

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What cosmic bodies can be seen with the naked eye from

Group of space bodies

What is the name of the nearest

What are celestial bodies?

Celestial bodies are objects that fill the Universe. Space objects include: comets, planets, meteorites, asteroids, stars, which necessarily have their own names.

The subjects of the study of astronomy are cosmic (astronomical) celestial bodies.

The sizes of celestial bodies that exist in the universal space are very different: from gigantic to microscopic.

The structure of the star system is considered on the example of the solar system. Planets move around the star (Sun). These objects, in turn, have natural satellites, dust rings, and an asteroid belt has formed between Mars and Jupiter.

On October 30, 2017, residents of Sverdlovsk will observe the asteroid Irida. According to scientific calculations, an asteroid of the main asteroid belt will approach the Earth by 127 million kilometers.

Based on spectral analysis and the general laws of physics, it has been established that the Sun consists of gases. The view of the Sun through a telescope is the granules of the photosphere creating a gas cloud. The only star in the system produces and radiates two types of energy. According to scientific calculations, the diameter of the Sun is 109 times the diameter of the Earth.

In the early 10s of the 21st century, the world was engulfed in yet another doomsday hysteria. Information was spread that the "planet of the devil" was carrying the apocalypse. The Earth's magnetic poles will shift as a result of the Earth being between Nibiru and the Sun.

Today, information about the new planet fades into the background and is not confirmed by science. But, at the same time, there are allegations that Nibiru has already flown past us, or through us, changing its primary physical indicators: comparatively reducing its size or critically changing its density.

What cosmic bodies form the solar system?

The solar system is the Sun and 8 planets with their satellites, the interplanetary medium, as well as asteroids, or dwarf planets, united in two belts - the near or main and the distant or Kuiper belt. Kuiper's largest planet is Pluto. This approach gives a concrete answer to the question: how many large planets are there in the solar system?

The list of known large planets of the system is divided into two groups - terrestrial and Jupiterian.

All terrestrial planets have a similar structure and chemical composition core, mantle and crust. This makes it possible to study the process of atmospheric formation on the planets of the inner group.

The fall of cosmic bodies is subject to the laws of physics

The Earth's speed is 30 km/s. The movement of the Earth together with the Sun relative to the center of the galaxy can cause a global catastrophe. The trajectories of the planets sometimes intersect with the lines of motion of other cosmic bodies, which is a threat that these objects will fall on our planet. The consequences of collisions or falls to Earth can be very severe. Paralyzing factors as a result of the fall of large meteorites, as well as collisions with an asteroid or a comet, will be explosions with the generation of colossal energy, and strong earthquakes.

Prevention of such space catastrophes is possible if the efforts of the entire world community are united.

When developing systems of protection and opposition, it is necessary to take into account the fact that the rules of behavior during space attacks should provide for the possibility of manifestation of properties unknown to mankind.

What is a cosmic body? What characteristics should it have?

The earth is considered as a cosmic body capable of reflecting light.

All visible bodies The solar system reflect the light of the stars. What objects are cosmic bodies? In space, in addition to clearly visible large objects, there are a lot of small and even tiny ones. The list of very small space objects begins with cosmic dust (100 microns), which is the result of gas emissions after explosions in planetary atmospheres.

Astronomical objects are different sizes, shapes and location relative to the Sun. Some of them are combined into separate groups to make it easier to classify them.

What are the cosmic bodies in our galaxy?

Our Universe is filled with various space objects. All galaxies are a void filled with different forms astronomical bodies. From school course astronomy we know about the stars, planets and satellites. But there are many types of interplanetary fillers: nebulae, star clusters and galaxies, almost unstudied quasars, pulsars, black holes.

Large astronomically - these are stars - hot light-emitting objects. In turn, they are divided into large and small. Depending on the spectrum, they are brown and white dwarfs, variable stars and red giants.

All celestial bodies can be divided into two types: those that give energy (stars) and those that do not (cosmic dust, meteorites, comets, planets).

Each heavenly body has its own characteristics.

Classification of cosmic bodies of our system according to composition:

• silicate;
• ice;
• combined.

Artificial space objects are space objects: manned spacecraft, manned orbital stations, manned stations on celestial bodies.

On Mercury, the Sun moves in the opposite direction. In the atmosphere of Venus, according to the information received, they suggest finding terrestrial bacteria. The Earth moves around the Sun at a speed of 108,000 km per hour. Mars has two satellites. Jupiter has 60 moons and five rings. Saturn is contracting at the poles due to its rapid rotation. Uranus and Venus revolve around the sun reverse direction. On Neptune there is such a phenomenon as.

A star is a hot gaseous cosmic body in which thermonuclear reactions take place.

Cool stars are brown dwarfs that do not have enough energy. Completes the list astronomical discoveries a cold star from the constellation Bootes CFBDSIR 1458 10ab.

White dwarfs are cosmic bodies with a cooled surface, inside of which the thermonuclear process no longer occurs, while they consist of high-density matter.

Hot stars are celestial bodies that emit blue light.

The temperature of the main star of the Beetle Nebula is -200,000 degrees.

A trace in the sky that glows can be left by comets, small shapeless space formations left over from meteorites, fireballs, various remnants of artificial satellites that enter the solid layers of the atmosphere.

Asteroids are sometimes classified as small planets. In fact, they look like stars of low brightness due to the active reflection of light. The largest asteroid in the universe is Cercera from the constellation Canis.

What cosmic bodies can be seen with the naked eye from Earth?

Stars are cosmic bodies that radiate heat and light into space.

Why are there planets in the night sky that don't emit light? All stars glow due to the release of energy during nuclear reactions. The resulting energy is used to contain gravitational forces and for light emissions.

But why do cold space objects also emit a glow? Planets, comets, asteroids do not radiate, but reflect starlight.

Group of space bodies

Space is filled with bodies of different sizes and shapes. These objects move differently relative to the Sun and other objects. For convenience, there is a certain classification. Examples of groups: "Centaurs" - located between the Kuiper belt and Jupiter, "Volcanoids" - presumably between the Sun and Mercury, 8 planets of the system are also divided into two: the inner (terrestrial) group and the outer (Jupiterian) group.

What is the name of the closest cosmic body to the earth?

What is the celestial body that orbits a planet called? Around the Earth, according to the forces of gravity, the natural satellite of the Moon moves. Some planets of our system also have satellites: Mars - 2, Jupiter - 60, Neptune - 14, Uranus - 27, Saturn - 62.

All objects subject to solar gravity are part of the vast and so incomprehensible solar system.

The fear of a comet impacting the Earth will always live in the hearts of our scientists. In the meantime, they will be afraid, let's remember the most sensational comets that have ever excited mankind.

Comet Lovejoy

In November 2011, Australian astronomer Terry Lovejoy discovered one of the largest comets of the near-solar Kreutz group, about 500 meters in diameter. She flew through the solar corona and did not burn out, was clearly visible from Earth and even photographed from the International Space Station.

Source: space.com

Comet McNaught

The first brightest comet of the 21st century, also called the "Big Comet of 2007". Discovered by astronomer Robert McNaught in 2006. In January and February 2007 it was perfectly visible to the naked eye to the inhabitants of the southern hemisphere of the planet. The next return of the comet is not soon - in 92,600 years.

Source: www.wyera.com

Comets Hale-Bopp and Hyakutake

Appeared one after another - in 1996 and 1997, competing in brightness. If the Hale-Bopp comet was discovered back in 1995 and flew strictly “on schedule”, Hyakutake was discovered only a couple of months before its approach to the Earth.

Source: website

Comet Lexell

In 1770, comet D/1770 L1, discovered by Russian astronomer Andrei Ivanovich Leksel, passed at a record close distance from the Earth - only 1.4 million kilometers. This is about four times farther than the Moon is from us. The comet was visible to the naked eye.

Source: solarviews.com

1948 eclipse comet

November 1, 1948 during the full solar eclipse astronomers suddenly discovered a bright comet near the sun. Officially named C/1948 V1, it was the last "sudden" comet of our time. It could be seen with the naked eye until the end of the year.

Source: philos.lv

Great January Comet 1910

Appeared in the sky a couple of months before Halley's comet, which everyone was waiting for. The first new comet was noticed by miners from the diamond mines of Africa on January 12, 1910. Like many superbright comets, it was visible even during the day.

Source: arzamas.academy

Great March Comet of 1843

It is also a member of the Kreutz family of near-solar comets. It flew only 830 thousand kilometers from the center of the Sun and was clearly visible from the Earth. Its tail is one of the longest of all known comets = 2 astronomical units (1 astronomical unit equals the distance between the Earth and the Sun).

Planets of the solar system

According to the official position of the International astronomical union(IAS), an organization that assigns names to astronomical objects, there are only 8 planets.

Pluto was removed from the category of planets in 2006. because in the Kuiper belt are objects that are larger / or equal in size to Pluto. Therefore, even if it is taken as a full-fledged celestial body, then it is necessary to add Eris to this category, which has almost the same size with Pluto.

As defined by MAC, there are 8 known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

All planets are divided into two categories depending on their physical characteristics: terrestrial groups and gas giants.

Schematic representation of the location of the planets

terrestrial planets

Mercury

The smallest planet in the solar system has a radius of only 2440 km. The period of revolution around the Sun, for ease of understanding, equated to the earth's year, is 88 days, while Mercury has time to complete a revolution around its own axis only one and a half times. Thus, its day lasts approximately 59 Earth days. For a long time it was believed that this planet is always turned to the Sun by the same side, since the periods of its visibility from the Earth were repeated with a frequency approximately equal to four Mercury days. This misconception was dispelled with the advent of the possibility of using radar research and conducting constant observations using space stations. The orbit of Mercury is one of the most unstable; not only the speed of movement and its distance from the Sun change, but also the position itself. Anyone interested can observe this effect.

Mercury in color, as seen by the MESSENGER spacecraft

Mercury's proximity to the Sun has caused it to experience the largest temperature fluctuations of any of the planets in our system. The average daytime temperature is about 350 degrees Celsius, and the nighttime temperature is -170 °C. Sodium, oxygen, helium, potassium, hydrogen and argon have been identified in the atmosphere. There is a theory that it was previously a satellite of Venus, but so far this remains unproven. It has no satellites of its own.

Venus

The second planet from the Sun, the atmosphere of which is almost entirely composed of carbon dioxide. It is often called the Morning Star and the Evening Star, because it is the first of the stars to become visible after sunset, just as before dawn it continues to be visible even when all other stars have disappeared from view. The percentage of carbon dioxide in the atmosphere is 96%, there is relatively little nitrogen in it - almost 4%, and water vapor and oxygen are present in very small amounts.

Venus in the UV spectrum

Such an atmosphere creates a greenhouse effect, the temperature on the surface because of this is even higher than that of Mercury and reaches 475 ° C. Considered the slowest, the Venusian day lasts 243 Earth days, which is almost equal to a year on Venus - 225 Earth days. Many call it the sister of the Earth because of the mass and radius, the values ​​​​of which are very close to the earth's indicators. The radius of Venus is 6052 km (0.85% of the earth). There are no satellites, like Mercury.

The third planet from the Sun and the only one in our system where there is liquid water on the surface, without which life on the planet could not develop. At least life as we know it. The radius of the Earth is 6371 km and, unlike the rest of the celestial bodies in our system, more than 70% of its surface is covered with water. The rest of the space is occupied by the continents. Another feature of the Earth is the tectonic plates hidden under the planet's mantle. At the same time, they are able to move, albeit at a very low speed, which over time causes a change in the landscape. The speed of the planet moving along it is 29-30 km / s.

Our planet from space

One revolution around its axis takes almost 24 hours, and full walkthrough the orbit lasts 365 days, which is much longer in comparison with the nearest neighboring planets. The Earth day and year are also taken as a standard, but this is done only for the convenience of perceiving time intervals on other planets. The Earth has one natural satellite, the Moon.

Mars

The fourth planet from the Sun, known for its rarefied atmosphere. Since 1960, Mars has been actively explored by scientists from several countries, including the USSR and the USA. Not all research programs have been successful, but water found in some areas suggests that primitive life exists on Mars, or existed in the past.

The brightness of this planet allows you to see it from Earth without any instruments. Moreover, once every 15-17 years, during the Opposition, it becomes the brightest object in the sky, eclipsing even Jupiter and Venus.

The radius is almost half that of the earth and is 3390 km, but the year is much longer - 687 days. He has 2 satellites - Phobos and Deimos .

Visual model of the solar system

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• Sun

  The sun is a star, which is a hot ball of hot gases at the center of our solar system. Its influence extends far beyond the orbits of Neptune and Pluto. Without the Sun and its intense energy and heat, there would be no life on Earth. There are billions of stars, like our Sun, scattered throughout the Milky Way galaxy.

• Mercury

  Sun-scorched Mercury is only slightly larger than Earth's moon. Like the Moon, Mercury is practically devoid of an atmosphere and cannot smooth out the traces of impact from the fall of meteorites, therefore, like the Moon, it is covered with craters. The day side of Mercury is very hot on the Sun, and on the night side the temperature drops hundreds of degrees below zero. In the craters of Mercury, which are located at the poles, there is ice. Mercury makes one revolution around the Sun in 88 days.

• Venus

  Venus is a world of monstrous heat (even more than on Mercury) and volcanic activity. Similar in structure and size to Earth, Venus is covered in a thick and toxic atmosphere that creates a strong Greenhouse effect. This scorched world is hot enough to melt lead. Radar images through the mighty atmosphere revealed volcanoes and deformed mountains. Venus rotates in the opposite direction from the rotation of most planets.

• Earth is an ocean planet. Our home, with its abundance of water and life, makes it unique in our solar system. Other planets, including several moons, also have ice deposits, atmospheres, seasons, and even weather, but only on Earth did all these components come together in such a way that life became possible.

• Mars

  Although details of the surface of Mars are difficult to see from Earth, telescope observations show that Mars has seasons and white spots at the poles. For decades, people have assumed that the bright and dark areas on Mars are patches of vegetation and that Mars might be a suitable place for life, and that water exists in the polar caps. When the Mariner 4 spacecraft flew by Mars in 1965, many of the scientists were shocked to see pictures of the bleak, cratered planet. Mars turned out to be a dead planet. More recent missions, however, have revealed that Mars holds many mysteries that have yet to be solved.

• Jupiter

  Jupiter is the most massive planet in our solar system, has four large moons and many small moons. Jupiter forms a kind of miniature solar system. To turn into a full-fledged star, Jupiter had to become 80 times more massive.

• Saturn

  Saturn is the most distant of the five planets that were known before the invention of the telescope. Like Jupiter, Saturn is made up mostly of hydrogen and helium. Its volume is 755 times that of the Earth. Winds in its atmosphere reach speeds of 500 meters per second. These fast winds, combined with heat rising from the planet's interior, cause the yellow and golden streaks we see in the atmosphere.

• Uranus

  The first planet found with a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet is so far from the Sun that one revolution around the Sun takes 84 years.

• Neptune

  Nearly 4.5 billion kilometers from the Sun, distant Neptune rotates. It takes 165 years to complete one revolution around the Sun. It is invisible to the naked eye due to its vast distance from Earth. Interestingly, its unusual elliptical orbit intersects with the orbit of the dwarf planet Pluto, which is why Pluto is inside Neptune's orbit for about 20 out of 248 years during which it makes one revolution around the Sun.

• Pluto

  Tiny, cold and incredibly distant, Pluto was discovered in 1930 and has long been considered the ninth planet. But after the discovery of Pluto-like worlds even further away, Pluto was reclassified as a dwarf planet in 2006.

The planets are giants

There are four gas giants located beyond the orbit of Mars: Jupiter, Saturn, Uranus, Neptune. They are in the outer solar system. They differ in their massiveness and gas composition.

planets solar system, not to scale

Jupiter

The fifth planet from the Sun and the largest planet in our system. Its radius is 69912 km, it is 19 times more earth and only 10 times smaller than the Sun. A year on Jupiter is not the longest in the solar system, lasting 4333 Earth days (incomplete 12 years). His own day has a duration of about 10 Earth hours. The exact composition of the planet's surface has not yet been determined, but it is known that krypton, argon and xenon are present on Jupiter in much large quantities than on the Sun.

There is an opinion that one of the four gas giants is actually a failed star. In favor of this theory speaks the most a large number of Jupiter has a lot of satellites - as many as 67. To imagine their behavior in the orbit of the planet, a fairly accurate and clear model of the solar system is needed. The largest of them are Callisto, Ganymede, Io and Europa. At the same time, Ganymede is the largest satellite of the planets in the entire solar system, its radius is 2634 km, which is 8% larger than the size of Mercury, the smallest planet in our system. Io has the distinction of being one of only three moons with an atmosphere.

Saturn

The second largest planet and the sixth largest in the solar system. In comparison with other planets, the composition is most similar to the Sun chemical elements. The surface radius is 57,350 km, the year is 10,759 days (almost 30 Earth years). A day here lasts a little longer than on Jupiter - 10.5 Earth hours. In terms of the number of satellites, it is not far behind its neighbor - 62 versus 67. The largest satellite of Saturn is Titan, just like Io, which is distinguished by the presence of an atmosphere. Slightly smaller than it, but no less famous for this - Enceladus, Rhea, Dione, Tethys, Iapetus and Mimas. It is these satellites that are the objects for the most frequent observation, and therefore we can say that they are the most studied in comparison with the rest.

For a long time, the rings on Saturn were considered a unique phenomenon, inherent only to him. Only recently it was found that all gas giants have rings, but the rest are not so clearly visible. Their origin has not yet been established, although there are several hypotheses about how they appeared. In addition, it was recently discovered that Rhea, one of the satellites of the sixth planet, also has some kind of rings.

This comet, measuring 3-5 km, is far from the only one that has received direct attention from interplanetary spacecraft. However, there is every reason to consider this meeting a landmark and, hopefully, historical.

The mission of the Rosetta probe is a logical consequence of the special, and one might say mystical, interest of mankind in "shaggy" (komḗtēs) luminaries, as the ancient Greeks called these celestial bodies. Below we will analyze in a popular form the knowledge accumulated by mankind about space "icebergs", and we will try to understand the great interest in them from the scientific community.

Punctual "grieper"

The history of documented observations of comets goes back several thousand years, most detailed description appearances of "shaggy" luminaries can be found in ancient Chinese chronicles.

Even then, the appearance of these luminaries was associated with mystical and most often tragic events. So the appearance of a bright comet in 240 BC. was interpreted as a sign of the imminent death of the Chinese empress. The same comet that appeared in the sky over Rome in 12 BC. already "predetermined" the fate of Agrippa, a close friend and son-in-law of Emperor Augustus. In the 6th century, she also “caused” drought and unrest in Byzantium, and in 1066, according to contemporaries, she unambiguously doomed England to the invasion of William the Conqueror, Duke of Normandy.

Halley's Comet on the Bayeux Tapestry, 1066

However, this comet was destined to play a very important role in the history of science. In 1682, the English astronomer Edmund Halley, having calculated the orbit of the bright comet he observed, noticed that it coincided with the orbits of the comets of 1531 and 1607. Assuming that we are talking about the same comet, he predicted its appearance at perigee (the point of the orbit closest to the sun) in 1758.

Her appearance, a month late in 1759, was more than enough to acknowledge the triumph of Newton's theory of gravitation. Halley's comet is now at the top of a huge list of comets observed since then. Its index 1P/1682 indicates that it is the first of the comets "returned" to the Sun, belongs to the group P - short-period comets and was discovered in 1682.

Halley's comet orbital parameters

Again, thanks to Halley's comet, which passed through the disk of the sun in 1910, astronomers were able to estimate approximate dimensions comet nuclei, it turned out to be less than 20 km. At the same time, for the first time, spectral analysis tail of the "shaggy" luminary, as it turned out, rich in poisonous cyanide and carbon monoxide. What caused a big panic in the same year, when the Earth passed through the tail of a comet, of course, groundless.

Image of Halley's comet in 1910

By the next arrival of the comet in 1986, humanity was no longer limited to observations from the Earth (rather unfavorable that year). A whole flotilla went to "intercept" the space "iceberg" spacecraft. The composition of Halley's Armada was as follows:

Halley's comet in 1986

Two Soviet probes "Vega 1" and "Vega 2", flying at a distance of about 9,000 km from the comet's nucleus, compiled a 3D map of the nucleus and transmitted 1500 images (picture below).

The European probe "Giotto", approaching the core at a distance of 605 km, thanks to the navigational assistance of Soviet devices (photo below).

Two Japanese probes "Suisei" and "Sakigake", approached the core at 150,000 and 7 million km, respectively.
- ISEE-3 (ICE) studied the tail of Halley's comet from the Lagrange point L1 (Earth-Sun system).

Illustration of Halley's Armada, which studied the comet in 86

was received great amount information about cometary matter, thousands of pictures of the nucleus have been taken. An estimate of the size of the comet's nucleus confirmed the observations of 1910 - the nucleus irregular shape 15/8km. A lot of experience has been gained in the interaction of different space agencies, in solving complex technological problems.

Unfortunately, the "year of Halley's comet" long awaited by the scientific community was overshadowed by two man-made disasters - the death of the Challenger crew and the accident at the Chernobyl nuclear power plant.

In addition to Halley's comet, astronomers count thousands of comets observed over the past 300 years. The cores range in size from several tens of meters to tens of kilometers, and are a mixture of dust and ice, most often water, ammonia and/or methane (the so-called Whipple's "dirty snowball" model). However, it is clear that many kernels may deviate from this model to some extent. So the Deep impact space probe, which dropped a “projectile” on the Tempel 1 comet in 2005, made it possible to establish that the comet consists mainly of a porous dust frame.

"Bombardment" of comet Tempel by the Deep impact probe and subsequent flyby near the comet by the Stardust probe

As the surviving bricks of the primary building material of the solar system, comets are of great interest to geology, chemistry and biology. Presumably, it was comets that delivered the main part of the water of its hydrosphere to Earth in ancient times. The spectral lines of many comets contain complex organic compounds down to amino acids and urea. Scientists suggest that comets, being incubators of complex organic compounds, could bring to Earth the chemical base for the emergence of life.

Approaching perihelion, comet nuclei, under the action of solar radiation, begin to spew huge volumes of gases, bypassing the liquid state of aggregation of melting ice (sublimation). The gases, in turn, carry along large masses of dust mixed in ice, which, together with ice particles, is blown away, under the influence of solar radiation and wind, in the opposite direction from the star.

Comet tails can be hundreds of millions of kilometers long. So, in 1996, the Ulysses space probe (NASA/ESA) unexpectedly passed through the tail of the 1996 Big Comet C/1996 Hyakutake… 500 million kilometers behind it!

However, comet tails are not always "straight" or directed back from the sun. Depending on the orbital features of the comet, its composition, solar wind, or interaction magnetic field sun with ionized matter of the "shaggy" luminary, the tail can be directed both perpendicularly and in the direction of solar radiation. Moreover, in one comet, the tail may consist of several differently directed parts, or even look like a huge gas-dust shell.

Comet 17Р/ Holmes is an example of the atypical structure of the gas and dust shell (coma) of a comet, the comparative dimensions of its coma with the Sun and Saturn are shown.

Since 1995, all comets are usually divided into classes: P/ - Short period comets, with an orbital period of less than 200 years. C/ - long-period comets, with an orbital period of more than 200 years. Х/ - comets with unknown orbital parameters (historical comets). D/ - collapsed or "lost" comets, and finally class A/ - asteroids mistaken for comets.

Comet Shoemaker-Levy 9 collided with Jupiter in 1994. The comet was later reclassified as a suicide bomber D/ 1993 F

The class index (most often P/) is usually preceded by serial number the comet's confirmed passage of perihelion (the closest point in the orbit), and after - the year of discovery. After the year of discovery, a letter is usually set indicating ½ of the month and the serial number of the discovery, for example, A for comets discovered in the first half of January and Y, respectively, for the second half of December. And at the end, the names of the discoverers are indicated. Thus, the nomenclature name of the Churyumov-Gerasimenko comet would look something like this: 67P/ 1969 R1. However, it is most commonly abbreviated as (n)P/Name of discoverer.

Special attention deserves the class of "extremal comets", passing extremely close to the Sun. Almost always they are fixed by space probes studying our star - SOHO and the "twins" Stereo A and B. It is assumed that the bulk of these comets are fragments of one giant comet that collapsed thousands of years ago (Kreutz comets)

"King's Harem" of planets

The main part of short-period comets, in turn, is divided into 4 large families, according to the parameters of the orbit and the gravitational influence of the “host” giant planet. Jupiter has the most numerous "family", it is to him that the following comets "belong":

19P/ Borelli, next to which the Deep Space 1 probe (NASA) worked in 2001;

103P/ Hartley 2, was studied by NASA's Deep Impact probe in 2010 (animation below), following the aforementioned visit of comet 9P/ Tempel (Tempel 1), another typical member of the "family";

Comet 81P/Wilda, near which NASA's Stardust probe was able to collect dust samples and bring them back to Earth in 2006;

Comet 67P / Churyumov-Gerasimenko, studied by the Rosetta probe (ESA), also belongs to the “king family” of planets in terms of its characteristics.

"Chaos" in the belt of "stability"

Some short-period comets, according to the version most popular among scientists, "arrive" to us from the outer boundaries of the Kuiper belt - the Scattered Disk (RD). RD, together with the Kuiper belt, is a huge disk of large icy bodies with a diameter of several tens of meters to thousands of kilometers (Pluto and Charon). Extending from a distance of 35 astronomical units (the orbit of Neptune), to the outer limits of 50 AU. (or 100 AU from RH) the belt has an estimated mass of 1-8 lunar masses (the asteroid belt is no more massive than 0.04 lunar masses). The Kuiper belt itself is generally stable, thanks to orbital resonances with Neptune and with each other.

Distribution map of known Kuiper belt objects (plot of distances in a.e.)

The current state of the Kuiper belt and the Oort cloud is associated with the ancient migration of Neptune to the outer regions of the solar system, under the influence of the resonances of Jupiter and Saturn. Part of the matter was ejected from the solar system, part, together with the Oort cloud, into its outer parts. Millions of other debris were thrown into the inner solar system, causing the late heavy bombardment 4-3.5 billion years ago.

The solar system before the "migration" of Neptune (purple orbit) - (a), during (b) and after (c). Green indicates the orbit of Uranus

To explain the instability of the outer, scattered disk, one will have to resort to the basics of celestial mechanics. The two main parameters of the orbit of a celestial body are the apocenter (the point of greatest distance from the surface of a planet or star, in the latter case they speak of apohelion) and the pericenter (the closest point of the orbit, or in the case of circulation around the sun - perihelion). The difference between these values ​​is expressed in the eccentricity of the orbit - the degree of its deviation from an ideal circle (e=0) to an ellipse (e>0, but<1) и дальше к параболе (е=1) и гиперболе (e>1)

In the last two cases, we are talking about the trajectory of non-return. Changing the parameters of the orbit is possible at any point, but the change in velocities at the perihelion (an increase in the apohelion during acceleration and a decrease during deceleration) and vice versa affect the apohelion most of all. And the stronger the eccentricity, the greater the effect of changing speeds. Moreover, the "sensitivity" of the orbit to disturbances increases with its height, since with an increase in the orbit, the speed of the body's orbital revolution decreases inversely (people familiar with the Orbiter and KSP simulators know this firsthand).

In the inner part of the solar system, in the zone of terrestrial planets and the asteroid belt, the orbital velocities of bodies are quite high (tens of km/s), and the eccentricities are relatively small. Therefore, for strong orbital perturbations, it is necessary to expend a lot of energy. At the outer edge of the Kuiper belt, in the scattered disk, the orbital velocities of bodies typically range from a few kilometers to a few hundred m/s, so even small gravitational perturbations or collisions change the eccentricity very much. The celestial body significantly increases its apohelion (acceleration), or decreases its perihelion (deceleration), heading towards the inner parts of the solar system.

Table of the difference in orbital velocities in the solar system? Mercury - Mars (Earth group), Jupiter - Neptune (giants) and Pluto (inner Kuiper Belt)

space truckers

However, according to the most common scientific community In our opinion, most short-period P/-class comets and all C/-class comets come to us from the supposed Oort cloud. The inner part of the Cloud has the form of a toroidal belt stretching for a distance of 2000 to 20,000 astronomical units (Hills cloud). The mass of this cloud is estimated at least two dozen masses of the Earth.

Comparative sizes of the orbits of the terrestrial planets against the background of the Kuiper belt, and, accordingly, the sizes of the latter against the background of the Oort cloud

The Hills cloud serves as a kind of nourishment for an outer, spherical cloud with a mass of several Earth masses, stretching from a distance of 20,000 AU. up to 1 light year, to the gravitational boundary of the solar system (Hill's sphere). It is the outer Oort cloud that is considered the main "supplier" of comets to the inner part of the solar system. Presumably, these are the remains of the primary " building material» of the solar system, so these objects are of great scientific interest. The effects of deceleration and acceleration described for the Kuiper belt are much stronger here, due to the extremely low orbital velocities of comets (meters per second).

Of the best known long-period comets of recent decades, comets C/1996 B2 Hyakutake, C/2006 R1, and C/2009 P1 McNaught should be noted. Having come to us from distant regions of the Oort cloud, both comets for the first and last time, having passed perihelion, left the solar system forever along a hyperbolic trajectory (eccentricity greater than 1).

C/1996 B2 Hyakutake in the firmament of the earth

C/ 2006 P1 McNaught ("The Big Comet of 2007") with another example of an arched "wrong" coma

In 2010, comet Elenin (C/2010 X1) intended to do the same, but Jupiter's gravitational perturbation "registered" the comet in the solar system, reducing the eccentricity below 1 (apohelion of about 500 AU). The famous "Big Comet of 1997" by Hale Bopp (C/1995 01) only intended to give another lap of honor at the perihelion of its almost perpendicular to the Earth's plane orbit. However, the inexorable gravity of Jupiter and this time reduced the perihelion of the comet by half - from 600 (orbital period 4800 years) to 350 AU (orbital period 2400 years).

"Big Comet 1997" by Hale Bopp

And perhaps the biggest astronomical disappointment of 2013 was the comet ISON (C/2012 S1), moving along a parabolic trajectory (e=1) from the very outskirts of the solar system, the celestial body literally fell apart when passing its perihelion.

Modeling the orbit history of our old friend Halley's comet showed that it also came into the solar system from the distant Oort cloud. The gravitational perturbations of the giant planets, as is the case with many other comets, "registered" it in the family of Neptune's comets. The apohelion of the comet's orbit barely touches the Kuiper belt (35 AU), and the perihelion passes closer than Venus at 88 million km from the Sun. The comet will next return to perihelion in 2061.

In conclusion, I would like to recall the words of Mark Twain, who, like me, was born in the year of the appearance of Halley's comet (albeit a difference of 150 years): “I came into this world with a comet and I will also leave with it when it arrives next year” (with ) 1909 Mr. Twain did indeed leave in 1910, and with him Leo Tolstoy and the famous Italian astronomer Schiaparelli. Agree, not the most boring company to travel around the solar system.

For readers, I sincerely wish to live to see that significant time, and let no man-made disasters or the death of idols spoil your impression of admiring the beauty of the famous space wanderer.