How a comet is formed. The most famous comets

> Halley

Comet Halley, captured in 1986

– comet of the Solar System: period of revolution, photo, history of research, year of Halley’s comet, eccentricity, when it arrives, semimajor axis.

Halley's Comet is a short-period comet that arrives at our planet every 75 years. The last time we saw her was in 1986. If you're wondering when it will arrive back, Earth expects it to return in 2061.

The comet was named after Edmund Halley, who investigated its arrivals in 1531, 1607 and 1682. He realized that all three comets were the only returning object. So he was able to predict that 1758 should be perceived as the year of Halley's Comet.

Halley did not live to see this moment, but his conclusions turned out to be correct. Moreover, his calculations showed that a certain category of comets constantly returns to Earth. In 1986, telescopes on Earth monitored the arrival of Halley's Comet, and some spacecraft even planned to take samples.

It is difficult to observe because the period of Halley's Comet spans decades. Therefore, scientists focus on other objects to compare and infer class characteristics. For example, the analysis of 67P/Churyumov-Gerasimenko showed that the composition of water on comets differs from that on Earth.

History of Halley's Comet

The first record of a comet was left in 239 BC. e. Listed in the Chinese chronicles of Shin Shi and Wen Xiang Tong Khao. The ancient Greeks left a record in 466 BC. e. The return was recorded in Babylon in 164 and 87. BC. These texts are important because they allow us to study its orbital path in the past.

The arrival in 1301 inspired the artist Giotto to paint The Star of Bethlehem, which tells the story of the victory of William the Conqueror. At that time, scientists thought that each event indicated the arrival of a new object. They were often seen as harbingers of disasters. This is also noticeable in Shakespeare's play Julius Caesar, where one of the lines says that comets mark the death of kings.

Detection of the periodicity of Comet Halley

Even during Shakespeare's lifetime, astronomers were inclined to believe that the Sun stood at the center of the solar system. Many years passed until a whole powerful concept was established that forces us to take a fresh look at our place in the Universe (the heliocentric system).

In 1705, Edmund Halley completed his study of 24 comets and published An Astronomical Summary of Comets, which noted the objects that arrived in 1337-1698. Three of them coincided in orbits and other parameters, and he assumed that they were all a single object. He also calculated that her arrival should be expected in 1758.

The comet arrived on time and was followed by inspired scientists from all over the world. Halley's Comet is shown in the photo below.

The comet's return in 1910 was especially impressive because it came within 22.4 million km of us. It was this year that we received her first photo. It's amazing that Mark Twain accurately predicted his death. He wrote that he arrived with the comet in 1835 and would leave with the next arrival. This happened on April 21, 1910.

Space Age

In 1986, humanity was able to use spaceships for the first time in research. And it was a good moment, because it came close to the planet. Several devices called “Halley's Armada” were sent to the comet. The Soviet-French mission Vega 1 and 2 went to the object and one even managed to image the core. Two probes also flew from Japan.

Photos of Halley's comet have also been received from NASA's International Cometary Explorer, which has been operating since 1978. The photographs were taken at a distance of 28 million km.

The arrival of the comet also marked a tragic event. The crew of the Challenger STS-51L planned to follow her. But on January 28, the ship exploded during takeoff and 7 astronauts died.

The re-arrival is still decades away, but we can keep track of cosmic remnants in space. We are talking about the Orionid meteor shower in October.

In 2061, Halley's Comet will be on the same side of the Sun as Earth and will be much brighter. Scientists believe its periodicity is still questionable because a collision with any object would push it back for thousands of years.

Its brightness is predicted to reach an apparent value of -0.3. There are also objects included in the “Halley family of comets.” They converge in orbital characteristics. But there are also inconsistencies, which means they may have a different origin. Perhaps they are members of the Oort cloud or created from the centaurs (between Jupiter and the Kuiper belt).

Scientists are not sitting idle while waiting for the comet. In 2014-2016 We had the amazing opportunity to visit comet 67P/Churyumov-Gerasimenko and analyze samples. In the same way, the researchers studied 81P/Wilda and 9P/Tempel.

Photos of Halley's Comet

Halley's Comet in 1986

Comet as seen at Table Mountain Observatory

On January 13, 1986, James Young photographed Halley's Comet from Table Mountain Observatory using a 24-inch reflecting telescope. The stripes created in the exhibition are stars in the territory of Aquarius. The image highlights the coma and the charged ion tail stretching over 725,000 km.

Comet in 1910

Comet reviewed by Giotto

On March 13, 1986, the multicolor camera of the Giotto spacecraft recorded a cometary nucleus at a distance of 600 km.

Halley's Comet in Diamond Mountain Review

Halley's Comet May Be Captured

Halley's Comet in Mount Wilson Survey

The outer space around us is constantly in motion. Following the movement of galactic objects, such as galaxies and clusters of stars, other space objects, including astroid and comets, also move along a clearly defined trajectory. Some of them have been observed by people for thousands of years. Along with the permanent objects in our sky, the Moon and planets, our sky is often visited by comets. Since their appearance, humanity has been able to observe comets more than once, attributing a wide variety of interpretations and explanations to these celestial bodies. For a long time, scientists could not give clear explanations when observing the astrophysical phenomena that accompany the flight of such a swift and bright celestial body.

Characteristics of comets and their differences from each other

Despite the fact that comets are a fairly common phenomenon in space, not everyone is lucky enough to see a flying comet. The thing is that, by cosmic standards, the flight of this cosmic body is a frequent occurrence. If we compare the period of revolution of such a body, focusing on earthly time, this is a rather long period of time.

Comets are small celestial bodies moving in outer space towards the main star of the solar system, our Sun. Descriptions of flights of such objects observed from Earth suggest that they are all part of the solar system, once participating in its formation. In other words, each comet is the remains of cosmic material used in the formation of planets. Almost all known comets today are part of our star system. Like planets, these objects are subject to the same laws of physics. However, their movement in space has its own differences and features.

The main difference between comets and other space objects is the shape of their orbits. If the planets move in the right direction, in circular orbits and lie in the same plane, then the comet rushes through space in a completely different way. This bright star, suddenly appearing in the sky, can move in the right or in the opposite direction, along an eccentric (elongated) orbit. This movement affects the speed of the comet, which is the highest among all known planets and space objects of our Solar System, second only to our main star.

The speed of Comet Halley when passing near the Earth is 70 km/s.

The plane of the comet's orbit does not coincide with the ecliptic plane of our system. Each celestial guest has its own orbit and, accordingly, its own period of revolution. It is this fact that underlies the classification of comets according to their orbital period. There are two types of comets:

• short-period with a circulation period from two to five years to a couple of hundred years;
• long-period comets that orbit with a period of two or three hundred years to a million years.

The first include celestial bodies that move fairly quickly in their orbit. It is customary among astronomers to designate such comets with the prefixes P/. On average, the orbital period of short-period comets is less than 200 years. This is the most common type of comet found in our near-Earth space and flying within the field of view of our telescopes. The most famous Comet, Halley, completes its run around the Sun in 76 years. Other comets visit our solar system much less frequently, and we rarely witness their appearance. Their orbital period is hundreds, thousands and millions of years. Long-period comets are designated in astronomy by the prefix C/.

It is believed that short-period comets became hostages to the gravitational force of the large planets of the solar system, which managed to snatch these celestial guests from the tight embrace of deep space in the Kuiper belt region. Long-period comets are larger celestial bodies that come to us from the far reaches of the Oort cloud. It is this region of space that is home to all comets, which regularly visit their star. Over millions of years, with each subsequent visit to the solar system, the size of long-period comets decreases. As a result, such a comet can become a short-period comet, shortening its cosmic life.

During observations of space, all comets known to this day have been recorded. The trajectories of these celestial bodies, the time of their next appearance within the solar system were calculated, and the approximate sizes were established. One of them even showed us his death.

The fall of the short-period comet Shoemaker-Levy 9 onto Jupiter in July 1994 was the most striking event in the history of astronomical observations of near-Earth space. A comet near Jupiter broke into fragments. The largest of them measured more than two kilometers. The fall of the celestial guest on Jupiter lasted for a week, from July 17 to July 22, 1994.

It is theoretically possible for the Earth to collide with a comet, but of the number of celestial bodies that we know today, not one of them intersects with the flight path of our planet during its journey. There remains the threat of a long-period comet appearing on the path of our Earth, which is still beyond the reach of detection means. In such a situation, a collision between the Earth and a comet could result in a catastrophe on a global scale.

In total, more than 400 short-period comets are known that regularly visit us. A large number of long-period comets come to us from distant, outer space, being born in 20-100 thousand AU. from our star. In the 20th century alone, more than 200 such celestial bodies were recorded. It was almost impossible to observe such distant space objects through a telescope. Thanks to the Hubble telescope, images of corners of space appeared, in which it was possible to detect the flight of a long-period comet. This distant object looks like a nebula with a tail millions of kilometers long.

Composition of the comet, its structure and main features

The main part of this celestial body is the comet's nucleus. It is in the nucleus that the bulk of the comet is concentrated, which varies from several hundred thousand tons to a million. In terms of their composition, the celestial beauties are icy comets, and therefore, upon close examination, they appear as dirty ice lumps of large sizes. In terms of its composition, an icy comet is a conglomerate of solid fragments of various sizes, held together by cosmic ice. As a rule, the ice of a comet's nucleus is water ice mixed with ammonia and carbon dioxide. Solid fragments consist of meteoric material and can be comparable in size to dust particles or, conversely, measure several kilometers in size.

In the scientific world, it is generally accepted that comets are cosmic deliverers of water and organic compounds in outer space. By studying the spectrum of the celestial traveler's core and the gas composition of its tail, the icy nature of these comic objects became clear.

The processes that accompany the flight of a comet in outer space are interesting. For most of their journey, being at a great distance from the star of our solar system, these celestial wanderers are not visible. Highly elongated elliptical orbits contribute to this. As the comet approaches the Sun, it heats up, which triggers the process of sublimation of space ice, which forms the basis of the comet's nucleus. In plain language, the icy base of the cometary nucleus, bypassing the melting stage, begins to actively evaporate. Instead of dust and ice, the solar wind breaks down water molecules and forms a coma around the comet's nucleus. This is a kind of crown of the celestial traveler, a zone consisting of hydrogen molecules. A coma can be enormous in size, stretching over hundreds of thousands or millions of kilometers.

As the space object approaches the Sun, the speed of the comet rapidly increases, and not only centrifugal forces and gravity begin to act. Under the influence of the Sun's attraction and non-gravitational processes, evaporating particles of cometary matter form the comet's tail. The closer the object is to the Sun, the more intense, larger and brighter the comet's tail, consisting of tenuous plasma. This part of the comet is the most noticeable and visible from Earth is considered by astronomers to be one of the most striking astrophysical phenomena.

Flying close enough to the Earth, the comet allows us to examine its entire structure in detail. Behind the head of a celestial body there is always a trail of dust, gas and meteoric matter, which most often ends up on our planet in the form of meteors.

The history of comets whose flight was observed from Earth

Various space objects constantly fly near our planet, illuminating the sky with their presence. With their appearance, comets often caused unreasonable fear and horror in people. Ancient oracles and stargazers associated the appearance of a comet with the beginning of dangerous periods of life, with the onset of cataclysms on a planetary scale. Despite the fact that the comet's tail is only a millionth of the mass of the celestial body, it is the brightest part of the space object, producing 0.99% of the light in the visible spectrum.

The first comet that was discovered through a telescope was the Great Comet of 1680, better known as Newton's Comet. Thanks to the appearance of this object, the scientist was able to obtain confirmation of his theories regarding Kepler's laws.

During observations of the celestial sphere, humanity managed to create a list of the most frequent space guests who regularly visit our solar system. High on this list is definitely Halley's Comet, a celebrity that has graced us with its presence for the thirtieth time. This celestial body was observed by Aristotle. The closest comet got its name thanks to the efforts of the astronomer Halley in 1682, who calculated its orbit and next appearance in the sky. Our companion flies within our visibility zone with regularity for 75-76 years. A characteristic feature of our guest is that, despite the bright trail in the night sky, the comet's nucleus has an almost dark surface, resembling an ordinary piece of coal.

In second place in popularity and celebrity is Comet Encke. This celestial body has one of the shortest orbital periods, which is equal to 3.29 Earth years. Thanks to this guest, we can regularly observe the Taurids meteor shower in the night sky.

Other most famous recent comets, which blessed us with their appearance, also have enormous orbital periods. In 2011, Comet Lovejoy was discovered, which managed to fly in close proximity to the Sun and at the same time remain unharmed. This comet is a long-period comet, with an orbital period of 13,500 years. From the moment of its discovery, this celestial guest will remain in the region of the solar system until 2050, after which it will leave the confines of near space for many 9000 years.

The most striking event of the beginning of the new millennium, literally and figuratively, was Comet McNaught, discovered in 2006. This celestial body could be observed even with the naked eye. The next visit to our solar system by this bright beauty is scheduled in 90 thousand years.

The next comet that may visit our sky in the near future will probably be 185P/Petru. It will become noticeable starting January 27, 2019. In the night sky, this luminary will correspond to the brightness of 11th magnitude.

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Every year on August 12, meteorites rapidly streak the sky throughout the night with bright fiery stripes, burning in the middle layers of the atmosphere. This fiery display is called the Perseus meteor shower. Moving in orbit, the Earth crosses a meteor shower - the trail of a comet making its way around the Sun.

What are comets?

Comets, like stone asteroids, are, so to speak, industrial waste after the formation of the Sun, planets and their satellites. Comets are composed mainly of ice with inclusions of small rocks and dust. For most of their lives, comets graze on vast desert grasslands on the periphery of the solar system.

The farthest planet in the solar system, Pluto, is located 5.8 billion kilometers from the Sun. A cluster of comets called Kuyper's Belt is located 480 million kilometers further than Pluto. Another similar cluster, the Oort Cloud, is 160 billion kilometers away from the Sun. In fact, the Oort Cloud is not a cloud, but a huge accumulation of trillions of comets, these comets roam the Universe in different directions, like cows in a grazing herd. The Oort Cloud is believed to surround the solar system like a huge halo.

Evidence of comet clusters

Proving the existence of comet clusters is very difficult. And that's why. Even if you fly in a rocket through the Oort Cloud, you may not encounter a single comet during the trip. They are separated by millions and billions of kilometers. Since comets are far from the Sun, they are very poorly illuminated and look almost as dark as the outer space surrounding them. Comets far from the Sun do not have the tails attributed to them. Their color is red-brown, their size is about two kilometers. In a word, they look like big dirty icebergs.

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Journey of comets

The comet's ugly face is transformed as it leaves the herd and approaches the Sun. At this moment, the comet undergoes an instant transformation. It stretches across the night sky in a long shining stripe, terrifying and delighting people. What force drives a comet out of the Oort Cloud? Naturally, gravity. This is how it happens. The sun rapidly flies through space and drags behind it an armful of planets, their satellites and comets. The path of the Sun runs among the stars of the Milky Way. A herd of comets, carried away by the Sun, sometimes flies close to another star. The force of its gravity produces a disturbance in the Oort Cloud, moving comets from their usual positions

From the distant depths of space, tailed “stars” are constantly approaching us and becoming accessible to observation from Earth. In 1987, for example, 17 new comets were discovered, and a total of 52 comets were observed during the year - a record number!

Over the entire history of human civilization, about 2000 appearances of comets have been observed (as of 2003). Information about 551 comets is limited only to a description of their appearance and brightness. For the rest, orbits were determined.

Dr. Marsden's catalog of cometary orbits, published in 2003, contains data on 1,679 different comets. Of these, 377 are periodic, that is, regularly returning to the Sun. Their circulation periods range from 3.3 years to 200 years. Some of the periodic comets have already been observed dozens of times, such as the most famous Comet Halley. But there are also comets (long-period), the period of revolution of which is measured in thousands and even millions of years.

Where do more and more comets come to us from? Where do they originate: in interstellar space or in the solar system itself?

The outstanding French astronomer and mathematician Pierre Laplace (1749-1827) at the end of the 18th century suggested that comets “come to the Sun from the outside, formed from the substance that makes up the nebulae.” But if comets were truly interstellar celestial bodies, they would have to move relative to the Sun at very high - hyperbolic speeds.

Meanwhile, a comet has never been observed to move in a clearly defined hyperbolic orbit. And if another comet described a path similar to a hyperbola, it was only under the influence of gravitational disturbances of the large planets near which it flew. Since comets move primarily in elliptical orbits before passing through the planetary system, we come to the conclusion that they are members of the Solar System. Comets constantly flying from all directions towards the Sun led the Estonian astronomer Ernst Epic to the idea that at a distance of about one light year from us there is a cloud of cometary bodies held by the gravity of the Sun.

In the middle of the 20th century, the outstanding Dutch astronomer Jan Oort (1900-1992) developed Epic's idea: he hypothesized the existence of a giant spherical cloud of cometary matter on the outskirts of the Solar System. As the scientist believed, it extends to a distance of up to 150 thousand astronomical units from the Sun, and its mass is approximately 0.1 the mass of the globe. And if we assume that the number of potential cometary nuclei (ice blocks) in the “cloud” reaches 100 billion, then the average mass of each such block should be about 6 billion tons.

Cometologists have calculated the initial orbits of almost parabolic comets. The results showed: the periphery of the Solar system is indeed saturated with cometary nuclei - the Oort cloud really exists. How did it come about?

When, in the process of forming a protoplanetary cloud from matter, the giant planets reached a large mass, they began to so strongly influence the movement of the clumps flying past them that they often “threw them out” to the boundaries of the Sun’s gravitational sphere. But, according to the cosmogonic hypothesis of Academician O. Yu. Schmidt, in the zone of formation of giants there was abundant freezing of gases onto dust particles. Therefore, the clumps of matter here represented blocks of contaminated ice.

Many such ice blocks were thrown to the outskirts of the solar system. It found itself surrounded on all sides by cometary matter. This is how the spherical Oort cloud appeared - a collection of distant icy satellites of the Sun. Here, in conditions of practically interstellar space, at a temperature close to absolute zero, cometary ices can persist for as long as desired.

But the icy cores of this cloud are too far from the Sun, and therefore their orbits are extremely unstable. Under the influence of disturbances from stars, some fragments of the “cloud” leave the solar system forever. Others, on the contrary, in almost parabolic, highly elongated orbits rush towards the central body and, thanks to a sharp increase in the flow of solar radiation, become ordinary comets.

This is how long-period comets can arise, that is, comets with a very long orbital period, reaching hundreds of thousands and even millions of years. For example, Comet Delavan, observed in 1914, will return to the Sun only after 24 million years!

If a long-period comet passes close to a planet, the latter’s gravity can transfer it to a less elongated orbit, and then it will become short-period. This apparently explains the presence of a large family of short-period comets near Jupiter, as well as the existence of families “associated” with Saturn, Uranus and Neptune. The famous Comet Halley also belongs to the Neptune family.

A particularly radical restructuring of cometary orbits occurs during close encounters of comets with giant planets. The most powerful "transformer" is Jupiter. Scientists from the Institute of Theoretical Astronomy E. I. Kazimirchak-Polonskaya and N. A. Belyaev showed with specific examples that Jupiter can not only capture a long-period comet, but also transfer it from one family to another, and in some cases even remove it to the outskirts of the Solar system or thrown into interstellar space. Comet Vesta, for example, during its approach to the Sun in 1976, acquired such great energy that it switched to a parabolic (open) orbit and therefore must leave the Solar system forever - fly away to other stellar worlds...

It has now been proven that in the solar system, in addition to the Oort cloud, there is also asteroid-comet belt beyond the orbit of Neptune. It, too, may be a rich source of new comets, and may be responsible for those seemingly inexplicable disturbances in Neptune's motion that have been erroneously attributed to Pluto.

Features of the orbits of short-period comets led Professor S.K. Vsekhsvyatsky (1905-1984) to the idea that the source of cometary fragments are the Galilean satellites of Jupiter - Io, Europa, Ganymede and Callisto. Flights of the American Voyager spacecraft actually discovered eruptions on Io up to 280 km high. But this does not mean that Io’s volcanoes are capable of throwing ice blocks into interplanetary space - the nuclei of future comets weighing millions and billions of tons.

But comets can be born as a result of asteroid-meteorite bombardment of the icy surfaces of satellites of giant planets. Bypassing the difficulties of the eruption hypothesis, this hypothesis well explains the constant emergence of new short-period comets in the Solar System, their connection with the orbits of the giant planets, the chemical composition of cometary ices and the mechanism of the ejection of large masses from the surfaces of satellites.

Well, perhaps this is one of the natural processes of the formation of new comets, which is not yet accessible to direct observations.