Small bodies of the solar system are. The most famous comets

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

On November 1, 1948, during a total solar eclipse, astronomers unexpectedly discovered a bright comet not far from 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).

The icy bodies of comets, usually several kilometers in diameter, are much less massive than planets. If a comet flies past a planet, its gravity is too weak to affect the planet's nearly circular orbit. On the other hand, the orbits of the comets themselves are not even circular at all. In most cases, they are so elongated that they look like parabolas. Unlike the planets, which move near the middle plane of the solar system, comets move in orbits arbitrarily oriented relative to this plane.

Apparently, the modern orbits of the comet are very different from the original ones. Moving in a typical orbit, the comet moves away from the Sun 1000 times further than Pluto. But when it enters the region of the planets, especially the powerful gravitational field of Jupiter, its orbit experiences strong perturbations. If the comet slows down as a result, it may move into a smaller orbit for a long time. If the perturbations increase the speed of the comet, it may leave the solar system altogether. Even if the comet's orbit initially lay in the plane of the solar system, planetary perturbations can take it out of this plane into an orbit such as is commonly observed in our time.

A good example of a planet-captured comet is Halley's Comet. The story of its discovery goes back to Newton, who showed how a comet's orbit could be calculated if its position in the sky could be measured over several nights. Using this method, Edmund Halley set about calculating the orbits of those comets that had been discovered in the preceding centuries. He was especially attentive to the comets of 1531, 1607 and 1682, whose orbits looked almost the same. In 1705, he came to the conclusion that this is the same comet, which, with an interval of 76 years, approaches the Sun in an elongated orbit. In addition, it turned out that the comets of 1305, 1380 and 1456 moved in almost the same orbit. So Halley predicted that this comet would reappear in 1758.

When the comet's predicted return was near, French astronomer Alexis Claude Clairaut (17131765) realized that planetary disturbances might have changed the comet's orbit so much that it might not return by the predicted time. Clairaut feared that the comet would return before he had finished his calculations, but he was lucky. Completed in the autumn of 1758, his calculations showed that the comet would become noticeable more than a year later than the predicted date and would not reach the point of the orbit closest to the Sun until March of the next year. Indeed, the comet was discovered at the end of 1758, and it approached the Sun at the moment indicated by Clairaut. Halley's successful prediction, supplemented by Clairaut's calculations, was hailed as a triumph for Newton's theory.
The comet was named after Halley, and all its subsequent returns in the vicinity of the Sun - in 1835, 1910 and 1986 - aroused general interest. Over the past 200 years, methods for calculating orbits have been so improved that the time of the comet's appearance in 1986 was known in advance with an accuracy of 5 hours. If there were no other forces acting on the comet, then the moment of its appearance could be calculated more accurately. But gases are evaporating from the nucleus of the comet, forming an extensive tail (see Fig. item 6). The outburst of gas acts like a small jet engine and affects the comet's motion in unpredictable ways.
Interesting changes in the orbits of comets can occur under the influence of perturbations from Jupiter. In 1770, Charles Messier discovered a comet flying almost exactly towards the Earth and passing only 2 million kilometers from us. Anders Leksel calculated the comet's orbit and found that its orbital period is only 5.6 years. She became the first representative of a new class of short-period comets. But during the next 10 years this comet did not appear,* and Leksel began to look for the cause. According to his calculations, in 1779 the comet passed near Jupiter, and its orbit changed so much that it would never again approach the Earth. The comet was discovered in a new orbit and is now called Leksel's Comet.
Leksel was probably the first scientist to understand how sensitive the three-body problem is to the initial conditions - the deterministic chaos mentioned above. This is evident from his unpublished commentary, written while calculating the orbit of comet Leksel. Interestingly, by the end of the 18th century, the non-deterministic nature of Newtonian mechanics was already known, although it was completely overshadowed by the deterministic work of d'Alembert, Clairaut and others.
Another example of orbital perturbation under the influence of Jupiter is the dim comet discovered in 1943 by Liisi Oterma (19152001), an employee of the University of Turku (Finland). Oterma calculated its orbit and was surprised to find that it was almost circular, in contrast to the very elongated orbits of other comets. Only one other comet with a similar circular orbit is known. According to Oterm's calculations, this orbit was temporary. Until 1937, the comet moved far from the Earth, beyond the orbit of Jupiter. The approach to Jupiter threw the comet into Jupiter's orbit, where it was discovered. Oterma calculated that the comet would return to its distant orbit after its next approach to Jupiter in 1963, which it did. Comet Oterma can now only be seen with large telescopes.

Finally, the famous Comet Shoemaker-Levy was captured by Jupiter from a near-solar orbit into an orbit around Jupiter. During a close approach to the planet, the comet's nucleus fell apart into at least 21 fragments. In 1994, telescopes across the Earth and even from space watched these fragments enter Jupiter's atmosphere and break apart. Although the size of the largest fragments did not exceed several kilometers, the collision sites were visible even with small ground-based telescopes (see inset).

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, the most detailed description of the appearance of "shaggy" stars 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 the approximate size of cometary nuclei, it turned out to be less than 20 km. At the same time, a spectral analysis was made for the first time of the tail of the "hairy" luminary, which turned out to be 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 of spacecraft went to "intercept" the space "iceberg". 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

A huge amount of information about the cometary substance was received, thousands of pictures of the nucleus were taken. An estimate of the size of the comet's nucleus confirmed the observations of 1910 - an irregularly shaped nucleus of 15/8 km. 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 comet Tempel 1, 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 the perihelion, comet nuclei, under the influence 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, the solar wind, or the interaction of the sun's magnetic field with the ionized matter of the "shaggy" star, 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 the serial number of the confirmed passage by the comet of perihelion (the closest point in the orbit), and after it is 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.

Particular 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 apohelion is most affected by changes in the velocities at the perihelion (an increase in the apohelion during acceleration and a decrease during deceleration) and vice versa. 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

But still, according to the most common opinion in the scientific community, 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 the 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 (С/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.

Comets are cosmic snowballs made up of frozen gases, rocks, and dust and are roughly the size of a small city. When a comet's orbit brings it close to the Sun, it heats up and spews out dust and gas, causing it to become brighter than most planets. Dust and gas form a tail that stretches from the Sun for millions of kilometers.

10 facts you need to know about comets

1. If the Sun were as big as a front door, the Earth would be the size of a coin, the dwarf planet Pluto would be the size of a pinhead, and the largest Kuiper Belt comet (which is about 100 km across, which is about one-twentieth of Pluto ) will be the size of a speck of dust.
2. Short-period comets (comets that complete one revolution around the Sun in less than 200 years) live in an icy region known as the Kuiper Belt, located beyond the orbit of Neptune. Long comets (comets with long, unpredictable orbits) originate in the far corners of the Oort Cloud, which is located at a distance of up to 100 thousand AU.
3. The days on the comet are changing. For example, a day on Halley's Comet ranges from 2.2 to 7.4 Earth days (the time it takes for a comet to make a full rotation around its axis). Halley's Comet makes a complete revolution around the Sun (a year on the comet) in 76 Earth years.
4. Comets - cosmic snowballs, consisting of frozen gases, rocks and dust.
5. The comet heats up as it approaches the Sun and creates an atmosphere or com. The lump can be hundreds of thousands of kilometers in diameter.
6. Comets do not have satellites.
7. Comets don't have rings.
8. More than 20 missions were sent to study comets.
9. Comets cannot support life, but may have brought water and organic compounds - the building blocks of life - through collisions with the Earth and other objects in our solar system.
10. Halley's Comet is first mentioned in Bayeux of 1066, which tells of the overthrow of King Harold by William the Conqueror at the Battle of Hastings.

Comets: Dirty Snowballs of the Solar System

Comets In our travels through the solar system, we may be lucky enough to encounter giant balls of ice. These are solar system comets. Some astronomers call comets "dirty snowballs" or "mud ice balls" because they are made up mostly of ice, dust, and rock debris. Ice can consist of both ice water and frozen gases. Astronomers believe that comets may be composed of the original material that formed the basis of the formation of the solar system.

Although most of the small objects in our solar system are very recent discoveries, comets have been well known since ancient times. The Chinese have records of comets that date back to 260 BC. This is because comets are the only small bodies in the solar system that can be seen with the naked eye. Comets orbiting the sun are quite a sight to behold.

comet tail

Comets are actually invisible until they begin to approach the Sun. At this point, they begin to heat up and an amazing transformation begins. The dust and gases frozen in the comet begin to expand and erupt at explosive speeds.

The solid part of a comet is called the comet's nucleus, while the cloud of dust and gas around it is known as the comet's coma. The solar winds pick up the material in the coma, leaving a tail behind the comet that spans several million miles. As the Sun illuminates, this material begins to glow. The comet's famous tail is eventually formed. Comets and their tails can often be seen from Earth and with the naked eye.

The Hubble Space Telescope captured Comet Shoemaker-Levy 9 as it hit Jupiter.

Some comets can have up to three separate tails. One of them will consist mainly of hydrogen, and is invisible to the eye. The other dust tail glows bright white, while the third plasma tail will typically take on a blue glow. As the Earth passes through these dust trails left by comets, the dust enters the atmosphere and creates meteor showers.

Active jets on Comet Hartley 2

Some comets fly in an orbit around the sun. They are known as periodic comets. A periodic comet loses a significant portion of its material each time it passes near the Sun. Eventually, after all this material is lost, they stop becoming active and roam the solar system like a dark ball of dust. Halley's Comet is probably the most famous example of a periodic comet. The comet changes its appearance every 76 years.

History of comets
The sudden appearance of these mysterious objects in ancient times was often seen as a bad omen and warning of natural disasters in the future. At the moment, we know that most comets are in a dense cloud located at the edge of our solar system. Astronomers call it the Oort Cloud. They believe that gravity from the accidental passage of stars or other objects could knock some of the comets out of the Oort Cloud and send them on a journey to the inner solar system.

Manuscript depicting comets from the ancient Chinese

Comets can also collide with the Earth. In June 1908, something exploded high in the atmosphere over the village of Tunguska in Siberia. The blast had the power of 1,000 bombs dropped on Hiroshima and flattened trees for hundreds of miles. The absence of any fragments of the meteorite led scientists to believe that it may have been a small comet that exploded on impact with the atmosphere.

Comets may also have been responsible for the extinction of the dinosaurs, and many astronomers believe that ancient cometary impacts brought most of the water to our planet. While there is a possibility that the Earth could be hit again by a large comet in the future, the chances of this event occurring within our lifetime are more than one in a million.

For now, comets just continue to be objects of wonder in the night sky.

The most famous comets

Comet ISON

Comet ISON has been the subject of the most coordinated observations in cometary history. Over the course of the year, more than a dozen spacecraft and numerous ground-based observers collected what is believed to be the largest data collection on the comet.

Known in the catalog as C/2012 S1, comet ISON began its journey towards the inner solar system about three million years ago. She was first seen in September 2012 at a distance of 585,000,000 miles. It was her very first journey around the Sun, meaning she was made from primordial matter that arose in the early days of the formation of the solar system. Unlike comets that have already made several passes through the inner solar system, Comet ISON's upper layers have never been heated by the Sun. The comet was a kind of time capsule in which the moment of the formation of our solar system was captured.

Scientists from all over the world have launched an unprecedented observation campaign, using many ground-based observatories and 16 spacecraft (all but four have successfully studied the comet).

On November 28, 2013, scientists watched as comet ISON was torn apart by the Sun's gravitational forces.

Russian astronomers Vitaly Nevsky and Artem Novichonok discovered the comet with a 4-meter telescope in Kislovodsk, Russia.

ISON is named after the night sky survey program that discovered it. ISON is a group of observatories in ten countries that are united to detect, monitor and track objects in space. The network is managed by the Institute of Applied Mathematics of the Russian Academy of Sciences.

Comet Encke

Comet 2P/Encke Comet 2P/Encke is a small comet. Its core is approximately 4.8 kilometers (2.98 miles) in diameter, about one-third the size of the object that supposedly killed the dinosaurs.

The period of revolution of a comet around the Sun is 3.30 years. Comet Encke has the shortest orbital period of any known comet within our solar system. Encke passed perihelion (the closest point to the Sun) in the past in November 2013.

Photograph of a comet taken by the Spitzer telescope

Comet Encke is the parent comet of the Taurid meteor shower. The Taurids, which peak in October/November of each year, are fast meteors (104,607.36 km/h or 65,000 mph) known for their fireballs. Fireballs are meteors that are as bright or even brighter than the planet Venus (when viewed in the morning or evening sky with an apparent brightness value of -4). They can create large bursts of light and color and last longer than the average meteor shower. This is due to the fact that fireballs come from larger particles of comet material. Often, this particular stream of fireballs occurs on or around the day of Halloween, making them known as Halloween Fireballs.

Comet Encke approached the Sun in 2013 at the same time that Comet Ison was much talked about and imagined, and because of this was photographed by both the MESSENGER and STEREO spacecraft.

Comet 2P/Encke was first discovered by Pierre F.A. Meshen on January 17, 1786. Other astronomers found this comet on subsequent passages, but these sightings were not determined to be the same comet until Johann Franz Encke calculated its orbit.

Comets are usually named after their discoverer(s) or after the name of the observatory/telescope used in the discovery. However, this comet is not named after its discoverer. Instead, it was named after Johann Franz Encke, who calculated the comet's orbit. The letter P indicates that 2P/Encke is a periodic comet. Periodic comets have an orbital period of less than 200 years.

Comet D/1993 F2 (Shoemakerov - Levy)

Comet Shoemaker-Levy 9 was captured by Jupiter's gravity, exploded, and then crashed into the giant planet in July 1994.

When the comet was discovered in 1993, it had already been broken up into more than 20 fragments traveling around the planet in a two-year orbit. Further observations showed that the comet (believed to be a single comet at the time) came close to Jupiter in July 1992 and was tidally torn apart by the planet's powerful gravity. The comet is believed to have orbited Jupiter for about ten years before its death.

A comet breaking into many pieces was rare, and seeing a comet captured in orbit near Jupiter was even more unusual, but the biggest and rarest discovery was that fragments had crashed into Jupiter.

NASA had a spacecraft that observed - for the first time in history - a collision between two bodies in the solar system.

NASA's Galileo orbiter (then on its way to Jupiter) managed to get a direct view of parts of the comet, labeled A through W, that were colliding with Jupiter's clouds. The clashes began on July 16, 1994 and ended on July 22, 1994. Many ground-based observatories and orbiting spacecraft, including the Hubble Space Telescope, Ulysses and Voyager 2, have also studied the collisions and their aftermath.

Comet impact on Jupiter

A "freight train" of fragments crashed on Jupiter with the force of 300 million atomic bombs. They created huge puffs of smoke that were 2,000 to 3,000 kilometers (1,200 to 1,900 miles) high and heated the atmosphere to very hot temperatures of 30,000 to 40,000 degrees Celsius (53,000 to 71,000 degrees Fahrenheit). Comet Shoemaker-Levy 9 left dark, ringed scars that were eventually erased by Jupiter's winds.

When the collision took place in real time, it was more than just a show. This has given scientists new insights into Jupiter, Comet Shoemaker-Levy 9, and cosmic collisions in general. The researchers were able to deduce the composition and structure of the comet. The impact also left behind dust that is found at the top of Jupiter's clouds. By observing the dust spreading across the planet, scientists were able to track the direction of high-altitude winds on Jupiter for the first time. And by comparing changes in the magnetosphere with changes in the atmosphere after the impact, scientists were able to study the relationship between the two.

Scientists estimate that the comet was originally about 1.5 - 2 kilometers (0.9 - 1.2 miles) wide. If an object of this size were to hit the Earth, it would have devastating consequences. The collision could send dust and debris into the sky, creating fog that would cool the atmosphere and absorb sunlight, shrouding the entire planet in darkness. If the fog lasts long enough, plant life will die - along with the people and animals that depend on them to survive.

These kinds of collisions were more frequent in the early solar system. Comet collisions probably occurred mainly because Jupiter lacked hydrogen and helium.

Currently, collisions of this magnitude are likely to occur only once every few centuries - and pose a real threat.

Comet Shoemaker-Levy 9 was discovered by Carolina and Eugene Shoemaker and David Levy in an image taken on March 18, 1993 with the 0.4-meter Schmidt Telescope on Mount Palomar.

The comet was named after its discoverers. Comet Shoemaker-Levy 9 was the ninth short-period comet discovered by Eugene and Caroline Shoemaker and David Levy.

Comet Tempel

Comet 9P/TempelComet 9P/Tempel orbits the Sun in an asteroid belt between Mars and Jupiter. The comet last passed its perihelion (the closest point to the Sun) in 2011 and will return again in 2016.

Comet 9P/Tempel belongs to the Jupiter family of comets. Jupiter-family comets are comets that have an orbital period of less than 20 years and orbit close to the gas giant. Comet 9P/Tempel takes 5.56 years to complete one complete orbit around the Sun. However, the comet's orbit gradually changes over time. When Tempel's Comet was first discovered, it had an orbital period of 5.68 years.

Comet Tempel is a small comet. Its core is about 6 km (3.73 miles) in diameter, which is thought to be half the size of the object that killed the dinosaurs.

Two missions were sent to study this comet: Deep Impact in 2005 and Stardust in 2011.

A possible impact trace on the surface of Comet Tempel

Deep Impact fired an impact projectile at a comet's surface, becoming the first spacecraft capable of extracting material from a comet's surface. The collision released relatively little water and a lot of dust. This suggests that the comet is far from being a "block of ice". The impact of the impact projectile was later captured by the Stardust spacecraft.

Comet 9P/Tempel was discovered by Ernst Wilhelm Leberecht Tempel (better known as Wilhelm Tempel) on April 3, 1867.

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Since Wilhelm Tempel discovered this comet, it is named after him. The letter "P" means that Comet 9P/Tempel is a short period comet. Short period comets have an orbital period of less than 200 years.

Comet Borelli

Comet 19P/Borelli Similar to a chicken leg, comet 19P/Borelli's small nucleus is about 4.8 kilometers (2.98 miles) in diameter, about a third the size of the object that killed the dinosaurs.

Comet Borelli orbits the Sun in the asteroid belt and is a member of the Jupiter family of comets. Jupiter-family comets are comets that have an orbital period of less than 20 years and orbit close to the gas giant. It takes about 6.85 years for it to complete one complete revolution around the Sun. The comet passed its last perihelion (nearest point to the Sun) in 2008 and will return again in 2015.

The Deep Space 1 spacecraft flew past Comet Borelli on September 22, 2001. Traveling at a speed of 16.5 kilometers (10.25 miles) per second, Deep Space 1 flew 2,200 kilometers (1,367 miles) above Comet Borelli's nucleus. This spacecraft took the best photograph of a comet nucleus ever.

Comet 19P/Borelli was discovered by Alphonse Louis Nicolas Borrelli on December 28, 1904 in Marseille, France.

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Alphonse Borrelli discovered this comet and that is why it is named after him. The letter "P" means that 19P/Borelli is a short-period comet. Short period comets have an orbital period of less than 200 years.

Comet Hale-Bopp

Comet C/1995 O1 (Hale-Bopp) Also known as the Great Comet of 1997, comet C/1995 O1 (Hale-Bopp) is a fairly large comet with a nucleus measuring up to 60 km (37 miles) in diameter. This is about five times the size of the alleged object, the fall of which led to the death of dinosaurs. Due to its large size, this comet was visible to the naked eye for 18 months in 1996 and 1997.

Comet Hale-Bopp takes about 2534 years to make one complete revolution around the Sun. The comet passed its last perihelion (nearest point to the Sun) on April 1, 1997.

Comet C/1995 O1 (Hale-Bopp) was discovered in 1995 (July 23), independently by Alan Hale and Thomas Bopp. Comet Hale-Bopp was discovered at an amazing distance of 7.15 AU. One AU is equal to about 150 million km (93 million miles).

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Since Alan Hale and Thomas Bopp discovered this comet, it is named after them. The letter "C" means That comet C/1995 O1 (Hale-Bopp) is a long period comet.

Comet Wild

Comet 81P/Wilde 81P/Wilda (Wilde 2) is a small oblate spherical comet about 1.65 x 2 x 2.75 km (1.03 x 1.24 x 1.71 miles). Its period of revolution around the Sun is 6.41 years. Comet Wild last passed perihelion (the closest point to the Sun) in 2010 and will return again in 2016.

Comet Wild is known as a new periodic comet. The comet orbits the Sun between Mars and Jupiter, but it hasn't always traveled this path. This comet originally orbited between Uranus and Jupiter. On September 10, 1974, gravitational interactions between this comet and the planet Jupiter changed the comet's orbit into a new shape. Paul Wild discovered this comet during its first revolution around the Sun in a new orbit.

Animated image of a comet

Since Wylda is a new comet (it didn't have as many orbits around the sun at close range), it's the perfect specimen for discovering something new about the early solar system.

NASA used this particular comet when, in 2004, they assigned the Stardust mission to fly to it and collect coma particles - the first collection of this kind of extraterrestrial material beyond the orbit of the Moon. These samples were collected in an airgel collector as the craft flew within 236 km (147 miles) of the comet. The samples were then returned to Earth in an Apollo-like capsule in 2006. In those samples, scientists discovered glycine: a fundamental building block of life.

Comets are usually named after their discoverer(s) or after the name of the observatory/telescope used in the discovery. Since Paul Wild discovered this comet, it was named after him. The letter "P" means that 81P/Wilda (Wild 2) is a "periodic" comet. Periodic comets have an orbital period of less than 200 years.

Comet Churyumov-Gerasimenko

Comet 67P / Churyumov-Gerasimenko may go down in history as the first comet to be landed by robots from the Earth and who will accompany it throughout its orbit. The Rosetta spacecraft, carrying the Phil lander, plans to rendezvous with this comet in August 2014 to escort it on its way to the inner solar system and back. Rosetta is a mission of the European Space Agency (ESA), which NASA provides with basic tools and support.

Comet Churyumov-Gerasimenko makes a loop around the Sun in an orbit that intersects the orbits of Jupiter and Mars, approaching, but not entering the orbit of the Earth. Like most Jupiter-family comets, it is believed to have fallen out of the Kuiper Belt, a region beyond the orbit of Neptune, in one or more collisions or gravitational tugs.

Surface of comet 67P/Churyumov-Gerasimenko close-up

Analysis of the comet's orbital evolution indicates that until the mid-19th century, the closest distance to the Sun was 4.0 AU. (about 373 million miles or 600 million kilometers), which is approximately two-thirds of the way from the orbit of Mars to Jupiter. Since the comet is too far from the heat of the Sun, it has not grown a coma (shell) or tail, so the comet is not visible from the Earth.

But scientists have calculated that a fairly close encounter with Jupiter in 1840 must have sent the comet flying deeper into the solar system, down to about 3.0 AU. (about 280 million miles or 450 million kilometers) from the Sun. The Churyumov-Gerasimenko perihelion (nearest approach to the Sun) stayed a little closer to the Sun for the next century, and then Jupiter gave the comet another gravitational hit in 1959. Since then, the comet's perihelion has stopped at 1.3 AU, about 27 million miles (43 million kilometers) beyond Earth's orbit.

Dimensions of comet 67P/Churyumov-Gerasimenko

The comet's nucleus is thought to be quite porous, giving it a density much lower than that of water. When heated by the Sun, a comet is believed to emit about twice as much dust as gas. A small detail known about the comet's surface is that Phila's landing site will not be chosen until Rosetta has taken a closer look at it.

During recent visits to our part of the solar system, the comet was not bright enough to be seen from Earth without a telescope. On this arrival, we will be able to see the fireworks up close, thanks to the eyes of our robots.

Discovered October 22, 1969 at the Alma-Ata Observatory, USSR. Klim Ivanovich Churyumov found an image of this comet while examining a photographic plate of another comet (32P/Comas Sola) taken by Svetlana Ivanova Gerasimenko on September 11, 1969.

67P indicates that it was the 67th periodic comet to be discovered. Churyumov and Gerasimenko are the names of the discoverers.

Comet Siding Spring

Comet McNaught Comet C/2013 A1 (Siding Spring) strafes toward Mars on October 19, 2014. The comet's nucleus is expected to pass the planet within a hair of space, which is 84,000 miles (135,000 km), about one-third the distance from Earth to the Moon and one-tenth the distance any known comet has passed Earth. This presents both an excellent opportunity to study and a potential hazard to spacecraft in this area.

Since the comet will approach Mars almost head-on, and since Mars is in its own orbit around the Sun, they will pass each other at a tremendous speed - about 35 miles (56 kilometers) per second. But a comet can have such a large ball that Mars can fly through high-speed particles of dust and gas for several hours. The Martian atmosphere will likely protect the rovers on the surface, but a spacecraft in orbit will be under a massive bombardment of particles moving two or three times faster than the meteorites that the spacecraft can normally withstand.

NASA spacecraft sends first photos of Comet Siding Spring back to Earth

"Our plans to use a spacecraft on Mars to observe Comet McNaught will be coordinated with plans for how orbiters can stay away from the flow and be protected if necessary," said Rich Zurek, chief scientist for the Mars Exploration Program at NASA Jet Propulsion Laboratories.

One way to protect the orbiters is to position them behind Mars during the most risky unexpected encounters. Another way is that the spacecraft "dodges" the comet, trying to protect the most vulnerable equipment. But such maneuvers can cause changes in the orientation of the solar arrays or antennas in such a way that this interferes with the ability of the vehicles to generate power and communicate with the Earth. "These changes will require a huge amount of testing," said Soren Madsen, chief engineer for the Mars exploration program at the Jet Propulsion Laboratory. “A lot of preparations need to be made now to prepare ourselves for the eventuality that we learn in May that the demonstration flight will be risky.”

Comet Siding Spring fell from the Oort Cloud, a huge spherical region of long-period comets that circles the solar system. To get an idea of ​​just how far that is, consider this situation: Voyager 1, which has been traveling in space since 1977, is much farther away than any of the planets, and has even emerged from the heliosphere, a huge bubble of magnetism and ionized gas. radiating from the sun. But it will take another 300 years for the ship to reach the inner "edge" of the Oort Cloud, and at its current speed of a million miles a day, it takes about 30,000 more years to finish passing through the cloud.

From time to time, some gravitational force - perhaps from passing by a star - pushes the comet free from its incredibly vast and distant storage, and it will fall into the Sun. This is what should have happened to Comet McNaught millions of years ago. All this time, the fall has been directed towards the inner part of the solar system, and it gives us only one chance in studying it. It is estimated that her next visit will be in about 740,000 years.

"C" indicates that the comet is not periodic. 2013 A1 shows that it was the first comet discovered in the first half of January 2013. Siding Spring is the name of the observatory where it was discovered.

Comet Giacobini-Zinner

Comet 21P/Giacobini-Zinner is a small comet with a diameter of 2 km (1.24 miles). The period of revolution around the Sun is 6.6 years. Comet Giacobini-Zinner last passed perihelion (its closest point to the Sun) on February 11, 2012. The next perihelion passage will be in 2018.

Each time comet Giacobini-Zinner returns to the inner solar system, its nucleus sprays ice and rocks into space. This debris flow leads to the annual meteor shower: the draconians that pass each year in early October. Draconids radiate from the northern constellation Draco. For many years, the flow is weak, and very few meteorites are seen during this period. However, there are occasional records of Draconid (sometimes called Jacobinid) meteor storms. A meteor storm is observed when a thousand or more meteors are visible within an hour at the observer's location. During its peak in 1933, 500 draconian meteors were seen within a minute in Europe. 1946 was also a good year for the draconians, with about 50-100 meteors seen in the US in one minute.

Coma and Nucleus of Comet 21P/Giacobini-Zinner

In 1985 (September 11) a redesignated mission called ICE (International Comet Explorer, formally International Sun and Earth Explorer-3) was assigned to collect data from this comet. ICE was the first spacecraft to follow a comet. ICE later joined the famous "armada" of spacecraft sent to Halley's Comet in 1986. Another mission, called Sakigaki, from Japan, was scheduled to follow this comet in 1998. Unfortunately, the spacecraft did not have enough fuel to reach the comet.

Comet Giacobini-Zinner was discovered on December 20, 1900 by Michel Giacobini at the Nice Observatory in France. Information about this comet was later restored by Ernst Zinner in 1913 (October 23).

Comets are usually named after their discoverer(s) or after the name of the observatory/telescope used in the discovery. Since Michel Giacobini and Ernst Zinner discovered and recovered this comet, it is named after them. The letter "P" means that comet Giacobini - Zinner is a "periodic" comet. Periodic comets have an orbital period of less than 200 years.

Comet Thatcher

Comet C/1861 G1 (Thatcher) Comet C/1861 G1 (Thatcher) takes 415.5 years to make one complete revolution around the Sun. Comet Thatcher passed its last perihelion (nearest point to the Sun) in 1861. Comet Thatcher is a long period comet. Long-period comets have an orbital period of more than 200 years.

When a comet passes around the Sun, the dust they emit is spread out into a dusty trail. Each year, as the Earth passes through this comet trail, space debris collides with our atmosphere, where it disintegrates and creates fiery colorful streaks in the sky.

Pieces of space debris emanating from Comet Thatcher and interacting with our atmosphere create the Lyrid meteor shower. This annual meteor shower occurs every April. The Lyrids are among the oldest known meteor showers. The first documented lyrid meteor shower dates back to 687 BC.

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Since A.E. Thatcher discovered this comet, it is named after him. The letter "C" means that Comet Thatcher is a long-period comet, that is, its orbital period is more than 200 years. 1861 is the year of its opening. "G" stands for the first half of April, and "1" means that Thatcher was the first comet discovered in this period.

Comet Swift-Tuttle

Comet Swift-Tuttle Comet 109P/Swift-Tuttle takes 133 years to complete one full orbit around the Sun. The comet passed its last perihelion (nearest point to the Sun) in 1992 and will return again in 2125.

Comet Swift-Tuttle is considered a large comet - its nucleus is 26 km (16 miles) across. (That's more than twice the size of the alleged object that killed the dinosaurs.) Pieces of space debris ejected from Comet Swift-Tuttle and interacting with our atmosphere create the popular Perseid meteor shower. This annual meteor shower occurs every August and reaches its peak in the middle of the month. Giovanni Schiaparelli was the first to understand that this comet was the source of the Perseids.

Comet Swift-Tuttle was discovered in 1862 independently by Lewis Swift and Horace Tuttle.

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Since Lewis Swift and Horace Tuttle discovered this comet, it is named after them. The letter "P" means that Comet Swift-Tuttle is a short-period comet. Short period comets have an orbital period of less than 200 years.

Comet Tempel-Tuttle

Comet 55P/Tempel-Tuttle is a small comet whose nucleus is 3.6 kilometers (2.24 miles) across. It takes 33 years for it to make one complete revolution around the Sun. Comet Tempel-Tuttle passed its perihelion (nearest point to the Sun) in 1998 and will return again in 2031.

Pieces of space debris emanating from the comet interact with our atmosphere and create the Leonids meteor shower. As a rule, this is a weak meteor shower, which peaks in mid-November. Every year, the Earth passes through this debris, which, when interacting with our atmosphere, breaks up and creates fiery colorful streaks in the sky.

Comet 55P/Tempel-Tuttle in February 1998

Every 33 years or so, the Leonids meteor shower turns into a true meteor storm, during which at least 1,000 meteors per hour burn up in the Earth's atmosphere. Astronomers in 1966 witnessed a spectacular sight: the remnants of a comet crashed into the Earth's atmosphere at a speed of a thousand meteors per minute during a 15-minute period. The last Leonid meteor storm was in 2002.

Comet Tempel-Tuttle was discovered twice independently - in 1865 and 1866 by Ernst Tempel and Horace Tuttle, respectively.

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Since Ernst Tempel and Horace Tuttle discovered it, the comet is named after them. The letter "P" means that Comet Tempel-Tuttle is a short-period comet. Short period comets have an orbital period of less than 200 years.

Comet Halley

Comet 1P/Halley is perhaps the most famous comet that has been observed for thousands of years. The comet is first mentioned by Halley in the Bayeux Tapestry, which tells of the Battle of Hastings in 1066.

Halley's comet takes about 76 years to make one complete revolution around the sun. The comet was last seen from Earth in 1986. That same year, an international armada of spacecraft converged on the comet to gather as much data as possible about it.

Halley's comet in 1986

The comet will not fly into the solar system until 2061. Every time Halley's comet returns to the inner solar system, its nucleus sprays ice and rock into space. This debris flow results in two faint meteor showers: the Eta Aquarids in May and the Orionids in October.

Dimensions of Comet Halley: 16 x 8 x 8 km (10 x 5 x 5 miles). It is one of the darkest objects in the solar system. The comet has an albedo of 0.03, which means it only reflects 3% of the light that hits it.

The first sightings of Halley's Comet are lost in time, over 2200 years ago. However, in 1705, Edmond Halley studied the orbits of previously observed comets and noted some that appeared to reappear every 75-76 years. Based on the similarity of the orbits, he suggested that it was in fact the same comet, and correctly predicted the next return in 1758.

Comets are usually named after their discoverer or the name of the observatory/telescope used in the discovery. Edmond Halley correctly predicted the return of this comet - the first prediction of its kind, and that is why the comet is named in his. The letter "P" means that Halley's comet is a short-period comet. Short period comets have an orbital period of less than 200 years.

Comet C/2013 US10 (Catalina)

Comet C/2013 US10 (Catalina) is an Oort Cloud comet discovered on October 31, 2013 at an apparent magnitude of 19 by the Catalina Sky Survey using a 0.68-meter (27-inch) Schmidt-Cassegrain telescope. As of September 2015, the comet has an apparent magnitude of 6.

When Catalina was discovered on October 31, 2013, observations of another object made on September 12, 2013 were used in a preliminary determination of its orbit, which gave an incorrect result, suggesting an orbital period of the comet of only 6 years. But on November 6, 2013, during a longer observation of the arc from August 14 to November 4, it became obvious that the first result on September 12 was obtained at another object.

By early May 2015, the comet had an apparent magnitude of 12 and was 60 degrees from the Sun as it moved further into the southern hemisphere. The comet arrived at solar conjunction on November 6, 2015, when it had a magnitude of about 6. The comet approached perihelion (its closest approach to the Sun) on November 15, 2015 at a distance of 0.82 AU. from the Sun and had a speed of 46.4 km/s (104,000 miles per hour) relative to the Sun, slightly more than the Sun's receding speed at that distance. Comet Catalina crossed the celestial equator on December 17, 2015 and became an object in the northern hemisphere. On January 17, 2016, the comet will pass 0.72 astronomical units (108,000,000 km; 67,000,000 miles) from Earth and should be magnitude 6, in the constellation Ursa Major.

Object C/2013 US10 is dynamically new. It came from the Oort Cloud from a loosely coupled, chaotic orbit that can easily be perturbed by galactic tides and passing stars. Before entering the planetary region (around 1950), Comet C/2013 US10 (Catalina) had an orbital period of several million years. After exiting the planetary region (around 2050), it will be on an ejection trajectory.

Comet Catalina is named after the Catalina Sky Survey, which discovered it on October 31, 2013.

Comet C/2011 L4 (PANSTARRS)

C/2011 L4 (PANSTARRS) is a non-periodic comet discovered in June 2011. It was only able to be seen with the naked eye in March 2013, when it was near perihelion.

It was discovered using the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) telescope, located near the top of Halican on the island of Maui in Hawaii. Comet C/2011 L4 likely took millions of years to travel from the Oort cloud. After leaving the planetary region of the solar system, the post-perihelion orbital period (epoch 2050) is estimated at about 106,000 years. Made of dust and gas, this comet's nucleus is about 1 km (0.62 miles) in diameter.

Comet C/2011 L4 was 7.9 AU away. from the Sun and had a brightness of 19 stars. led when it was discovered in June 2011. But already at the beginning of May 2012, it revived to 13.5 stars. led., and this was noticeable visually when using a large amateur telescope from the dark side. As of October 2012, the coma (an expansion of a rarefied dusty atmosphere) was about 120,000 kilometers (75,000 miles) in diameter. Without optical assistance, C/2011 L4 was seen on February 7, 2013 and had 6 stars. led. Comet PANSTARRS was observed from both hemispheres in the first weeks of March, and it passed closest to the Earth on March 5, 2013 at a distance of 1.09 AU. It approached perihelion (the closest approach to the Sun) on March 10, 2013.

Preliminary estimates predicted that C/2011 L4 would be brighter at around 0. led. (approximate brightness of Alpha Centauri A or Vega). October 2012 estimates predicted it could be brighter, with -4 stars. led. (roughly corresponds to Venus). In January 2013, there was a noticeable drop in brightness, which suggested that it could be brighter, with only +1 stars. led. In February, the light curve slowed further, suggesting a perihelion of +2. led.

However, a study using a secular light curve indicates that comet C/2011 L4 experienced a "braking event" when it was at a distance of 3.6 AU. from the Sun and had 5.6 AU. The brightness growth rate slowed down, and the magnitude at perihelion was predicted to be +3.5. For comparison, at the same perihelion distance, Halley's comet will have -1.0 mag. led. The same study concluded that C/2011 L4 is a very young comet and belongs to the "baby" class (that is, those whose photometric age is less than 4 years of the comet).

Image of comet Panstarrs taken in Spain

Comet C/2011 L4 reached perihelion in March 2013, and was estimated by various observers around the planet to have an actual peak of +1. led. However, its low location above the horizon makes it difficult to obtain certain data. This was facilitated by the lack of suitable reference stars and the obstruction of differential atmospheric extinction corrections. As of mid-March 2013, due to the brightness of twilight and low position in the sky, C/2011 L4 was best seen with binoculars 40 minutes after sunset. On March 17-18, the comet was not far from the star Algenib with 2.8 stars. led. April 22 near Beta Cassiopeia, and May 12-14 near Gamma Cephei. Comet C/2011 L4 continued to move north until May 28.

Comet PANSTARRS bears the name of the Pan-STARRS telescope, with which it was discovered in June 2011.

The composition of the solar system includes not only the Sun and 8 large planets. A huge number of different smaller objects also rotate in different orbits around the Sun. All of them also deserve their study.

Small bodies include:
- "dwarf planets" (this term was introduced after the abolition of the status of a planet for Pluto and all objects similar to it);
- asteroids, or "minor planets";
- comets;
- meteoritic bodies or meteoroids (i.e., just small stones);
- dust and gas.

dwarf planets

The term "dwarf planets" was introduced by the decision of the XXVI General Assembly of the International Astronomical Union (IAU) in 2006. After a heated debate, it was decided that Pluto, which is smaller than all the other planets in the solar system and even their large satellites, should be deprived of its status as a planet, which has been with Pluto since its discovery in 1930, and instead introduce for it and some other objects discovered by that time on the outskirts of the solar system, the mass of which was comparable to the mass of Pluto, a special definition of "dwarf planet". The following set of criteria has been proposed in order to determine whether an object belongs to the group of dwarf planets:
1) a dwarf planet revolves around the sun:
2) the gravitational force of the dwarf planet is sufficient to give it a spherical shape;
3) the dwarf planet does not clear the space around itself (so that there are no other bodies comparable in size next to it);
4) is not a satellite of another planet;

Currently, Pluto itself, Ceres (the largest object in the near asteroid belt) and Eris (a recently discovered object in the Kuiper belt, located even further than Pluto) fall under the definition of "dwarf planets", and for several more objects, classifying them as dwarf planets is being considered.

Characteristics of Pluto

average orbit radius: 5,913,520,000 km
diameter: 2370 km
weight: 1.3 *10^22 kg

Pluto's orbit is mostly beyond Neptune's, but has a large eccentricity, causing Pluto to sometimes be closer to the Sun than Neptune. The orbital period is 245.73 years. Any details on Pluto cannot be seen through a telescope, and after its discovery in 1930, for a long time it was mistakenly believed that the size and mass of Pluto were close to those of the earth. In fact, Pluto is more than 5 times smaller than the Earth in size and 500 times smaller in mass. It is also smaller than the moon. Pluto is also known to have five moons. The largest of them is Charon, discovered in 1978, it is only about 2 times smaller than Pluto itself.

In July 2015, NASA's New Horizons spacecraft reached Pluto for the first time. It flew within less than 10,000 km of Pluto and took pretty good photos of the surface. Mountains more than 3 thousand km high were found on Pluto, presumably consisting of ice, but most of the surface is plains.

Asteroids, the Kuiper belt and the Oort cloud

An asteroid is a small planet-like body in the solar system that orbits around the sun. The first asteroid Ceres was accidentally discovered by the Italian Piazzi on January 1, 1801, after which 3 more large asteroids were discovered within a few years. Then there was a break in the discovery of asteroids, and after 1835 they began to be discovered in large numbers. Currently, tens of thousands of asteroids are known. It is assumed that in the solar system there may be from 1.1 to 1.9 million objects larger than 1 km.

Most of the asteroids discovered so far have similar orbits between Mars and Jupiter. Obviously, the strong gravitational field of Jupiter during the formation of the solar system prevented the formation of another planet in this place.
Despite the very large number of asteroids, the vast majority of them are extremely small in size, and the total mass of the entire near asteroid belt is estimated at only 4% of the mass of the Moon. Several asteroids have been studied up close and photographed by spacecraft.

asteroid Ida and its small satellite

Subsequently, it became clear that there are more than one such belts, in which many small bodies revolve around the Sun. In the early 1950s, Oort and Kuiper proposed the existence of such belts beyond the orbit of Neptune. The Kuiper belt is located at a distance of about 30-50 astronomical units from the Sun and, according to astronomers, there are tens of thousands of objects larger than 100 km only. The mass of the Kuiper belt significantly exceeds the mass of the near asteroid belt. To date, more than 800 objects have been discovered in the Kuiper belt. The Oort Cloud, from which, according to calculations, some long-period comets occasionally arrive at the Sun, is even further away than the Kuiper belt.

Kuiper belt and Oort cloud.

Largest objects in the Kuiper Belt.
Below is Earth for comparison.

The word "comet" in Greek means "hairy", "long-haired". Comets flying across the sky have been observed by people from time to time since ancient times. It was believed that the appearance of comets bodes various bad omens.

In 1702, Edmund Halley proved that the comets observed in 1531, 1607 and 1682 are in fact not different comets, but the same one, which, moving along its orbit around the Sun, periodically returns after a certain period of time. This comet was named after him - Halley's comet.

The orbits of most comets are highly elongated ellipses. Presumably, comets come from the Oort cloud, which contains a huge number of small objects rotating at a great distance from the Sun. Under the influence of various reasons, some of these objects change their trajectory from time to time and approach the Sun, becoming comets.
When a comet approaches the Sun, the frozen gases on its surface begin to evaporate and form a huge tail that follows the comet for millions of kilometers. Under the pressure of solar radiation and solar wind, the tail of comets always points away from the Sun. Due to constant evaporation, the comet's nucleus gradually decreases in mass and eventually collapses, leaving only a mass of small fragments in its place. Sometimes, when the Earth crosses the orbits of former comets, masses of small particles fly into the atmosphere, forming a meteor shower.

Some comets have been studied by spacecraft, for example, the Soviet Vega in 1986 studied Halley's comet, and in 2005 NASA's Deep Impact spacecraft was deliberately brought into collision with the nucleus of comet Tempel.

Meteor bodies, dust and gas

According to the adopted agreements, bodies with dimensions greater than 1 km should be considered asteroids. Smaller objects are considered metoriids or meteoroids. The number of such objects in the solar system is enormous.
Sometimes objects flying in space get in the way of the Earth. For a long time, in the early stages of the existence of the solar system, collisions of planets with different bodies, including very large ones, happened often - this is evidenced, in particular, by numerous craters on the surface of the Moon and other celestial bodies. Now the probability of a collision of the Earth with a large object is small, but it still exists, so it is important to study outer space and identify objects whose orbits can intersect with the Earth's orbit.
Small space objects on the path of the Earth come across all the time. Flying into the atmosphere, most of them burn up at high altitude, not having time to reach the surface. Such objects that look like shooting stars are called meteors. Very rarely come across sufficiently large objects that do not have time to completely burn out in the atmosphere and fall to the surface of the Earth. Such objects are called meteorites. Meteorites are mainly stone, as well as iron and iron-stone. Interestingly, the most ancient iron products were made by people from meteoric iron. It is extremely rare that large objects that can cause severe damage can fall to Earth. It is assumed that the fall of a large asteroid to Earth 65 million years ago, the crater from which was found at the bottom of the Gulf of Mexico, could serve as one of the reasons for the extinction of dinosaurs.

Interplanetary space is not empty. There is a lot of fine interplanetary dust in the solar system. Its reserves are replenished all the time due to the destruction of comets, collisions of asteroids, etc. In addition, the solar wind, a stream of particles emanating from the Sun, penetrates far beyond the orbit of Pluto. The concentration of gas and dust in the solar system is much higher than in interstellar space.