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The simplest classification of bodies in the solar system is as follows:
The small bodies of the solar system include cosmic bodies that are neither planets, nor dwarf planets, nor their satellites. These are comets, asteroids, centaurs, damocloids, meteoroids, interplanetary gas and dust. Their total mass is negligible compared to the big planets, not to mention the Sun.
Asteroid(the term "asteroid" was introduced by William Herschel; "asteroid" means "star-like"; in the field of view of the telescope it looks like an asterisk) - a relatively small cosmic body that is part of the solar system and orbits around the sun. Asteroids are significantly inferior in mass to the planets, have an irregular shape and do not have an atmosphere. Asteroids can have satellites (for example, the asteroid Ida and its satellite Dactyl). Until 2006, asteroids were also called small planets. Today the term "minor planet" is not used.
The first asteroid (named Ceres) was discovered on January 1, 1801 by the Italian astronomer Giuseppe Piazzi. Before that, no one suspected the existence of asteroids.The diameter of Ceres is about 950 km.For some time, Ceres was considered a full-fledged planet, then it was given the status of an asteroid. Since August 24, 2006, Ceres has been classified as a dwarf planet.
The second discovered asteroid (1802) was named Pallas. The first asteroids were named after Greek and Roman goddesses.
By the end of 2011, about 85,000,000 asteroids were known, over 560,000 of them wereassigned official numbers andthe parameters of their orbits are precisely determined. Most of the asteroids known today are concentrated in the so-called main asteroid belt located between the orbits of Mars and Jupiter:
Ceres is the largest object in this belt, although it is no longer an asteroid. The largest asteroids are Vesta and Pallas (diameters are about 500 km). Vesta is the only asteroid that can sometimes be seen with the naked eye in the starry sky at the limit of human vision.
Asteroids are combined into groups and families based on the characteristics of their orbits. Asteroid groups- fairly free education, while families- denser gatherings (formed as a result of the destruction of large asteroids). Large families of asteroids can contain hundreds of large and hundreds of thousands of small asteroids.The asteroids in the family have similar orbital shapes, the largest and smallest distances from the Sun, and the periods of revolution around it are approximately the same.On the this moment About 25 families of asteroids are known. For example, the family of Eunomia, the family of Flora, the family of Vesta, the family of Themis...
There are asteroids that move in the same orbits as the major planets of the solar system. These groups of asteroids form equilateral triangles with the planet and the Sun. One group is ahead of the planet, the other follows the planet at the same distance. These groups of asteroids are named Trojans(one of the groups of Trojan asteroids of Jupiter was named by the Greeks - in honor of the Greeks - a participant in the Trojan War):
These groups do not break up and move steadily along the orbit of the planet ("captive asteroids"). Mars, Jupiter, Saturn, Uranus and Neptune have their own Trojans. In 2010, the first Trojan asteroid was also discovered near the Earth (diameter about 300 meters).
The surface of large asteroids is covered with craters, dust and rubble, while small asteroids are covered only with dust and rubble.
The larger and heavier the asteroid, the more dangerous it poses, however, it is much easier to detect it in this case. The most dangerous at the moment is the asteroid Apophis, with a diameter of about 300 m, in a collision with which, in the event of an accurate hit, it can be destroyed Big city, however, such a collision does not pose any threat to humanity as a whole. Asteroids more than 10 km across can represent a global danger. All asteroids of this size are known to astronomers and are in orbits that cannot lead to a collision with the Earth.At the moment, there are no asteroids that could threaten the Earth.
In 1992, a second asteroid belt was discovered beyond the orbit of Neptune, which was named Kuiper belt.
It is about 20 times wider and many times more massive than the main asteroid belt. Kuiper belt objects, unlike main belt asteroids, consist mainly of frozen volatile substances - water, methane and ammonia ice. Now more than a thousand Kuiper belt objects have been discovered (there may be several tens of thousands of objects with a diameter of more than 100 km). The largest of them: Kvaoar (1100 km), Ork (950 km), Ixion (800 km). Many dwarf planets move in the same region of space (for example, Pluto,Eris, Sedna).
A space body with a diameter of less than 100 meters is classified as a meteoroid or meteoroid. meteoroid- a solid cosmic body, intermediate in size between an asteroid and interplanetary dust. Small meteoric bodies (several millimeters in diameter), invading at high speed (11-72 km / s) into the upper layers of the Earth's atmosphere, heat up and burn out due to air friction. The phenomenon of the flash and burning of a meteor body, visible from the surface of the Earth, is called meteor. Usually during the night you can see 3-5 meteors in different parts of the sky. Such meteors are called sporadic. But sometimes the number of meteors increases, and it seems as if they are flying out of a certain area of the sky. If we continue the visible paths of meteors, then they will intersect at approximately one point - radiant. Then it is customary to talk about the activity of a certain meteor shower.
meteor shower- this is a celestial phenomenon, which is a consequence of the passage of the Earth through a swarm of meteoroids, which is a cloud of small solid particles - the remains of collapsed or collapsing comets. Meteor swarms, like the comets that gave birth to them, revolve around the Sun in orbits. The Earth on the same dates of the year passes through the same meteor swarms. There are 20-30 known meteor swarms and, accordingly, the same number of meteor showers. In August, there is a meteor shower, the radiant of which is in the constellation Perseus. These are the famous Perseids.
Comet- This is a small icy cosmic body that revolves around the Sun in a highly elongated orbit. The comet has a nucleus, consisting of ordinary water ice with an admixture of frozen gases - carbon dioxide (CO 2) and methane (CH 4), as well as small solid particles (they then become meteors). Comet nuclei are from several kilometers to tens of kilometers across. Nuclei surrounded coma- foggy shell of gases and dust. Away from the Sun, comets do not have tails, but as they approach the star, the evaporation of gases from the nucleus and the release of solid particles increase, the coma increases. The solar wind carries it to the side, a tail is formed. The closer the comet approaches the Sun, the longer the tail becomes, sometimes reaching tens of millions of kilometers. The comet's tail is directed away from the Sun.Famous Russian astronomer F. Bredikhin developed the theory of tails and forms of comets. He proposed to divide comet tails into three types:
- narrow and straight, directed away from the Sun;
- wide and slightly curved;
- short and strongly deviated from the Sun.
A comet can have two or even three tails at the same time.
When a comet passes the perihelion point of its orbit, its destruction becomes especially intense. Since many comets return to the Sun periodically, they are called periodic comets. If the period is short - less than 200 years - it is called short period comet(for example, Halley's comet, which arrives once every 76 years). Today, more than 400 short-period comets are known. If the period is large - more than 200 years - then it is called a long-period comet (for example, comets Hale-Bopp, McNaught, Lyulin ...). Sooner or later periodic comets are destroyed.
There are also non-periodic, "disposable" comets. The Dutch astronomer Jan Oort put forward the theory of the existence on the outskirts of the solar system (100 - 150 thousand AU from the Sun) of a giant cloud consisting of ice blocks.The cloud has since been called Oort cloud.
If, for one reason or another, any of the blocks gradually approaches the Sun, then it becomes a comet. Many such comets fly up to the Sun only once, after which they forever move away from it back into their comet cloud. The Kuiper Belt and Oort Cloud Objects are often referred to as trans-Neptunian (i.e. beyond-Neptunian) objects.
Comets can revolve not only around the Sun, but also around the largest planets - Jupiter and Saturn. Some comets then collide with these planets. For example, in 1994 the comet Shoemaker-Levy-9 (2 years before that it broke up into 22 fragments) collided with the planet Jupiter.
A larger meteoroid gives a brighter flash, which is called fireball(More precisely, a fireball is defined as a meteor whose brightness is greater than -4 m or a body whose apparent size is distinguishable). Large meteoroids may not have time to burn up in the atmosphere and fall to the Earth's surface. A meteorite that has fallen is called a meteorite., and one that can be found and touched. For example, Tunguska meteorite it is incorrect to call it a meteorite because it has not been discovered. More correctly - the Tunguska body. Most likely it was an ice fragment of a comet, which evaporated during the fall.
It is believed that 5-6 tons of meteorites fall on the Earth's surface in 1 day. After a meteorite collides with a solid surface, a round depression remains - crater("crater" in Greek means "bowl"). Giant craters several hundred kilometers across are sometimes referred to as astroblems("blema" in Greek means "wound").
For centuries, no matter how they called meteorites - and aerolites, and siderolites, and uranoliths, and meteorites, as well as celestial, air, atmospheric and meteor stones!
Most often fall to the ground stone meteorites(consists mainly of silicate rocks) - 93% of all falls. fall less often iron meteorites(consist of an iron-nickel alloy) - 6% of all falls. 1% of all falls are iron-stony meteorites. It is clear that meteorites cannot be fragments of ice comets. These are fragments of asteroids.
In 1977, an asteroid with a diameter of 166 km was discovered, in which in 1988 a coma was discovered, like a comet. With the removal of the object from the Sun, the coma disappeared. This object with a dual nature (asteroid-comet) was called Chiron. In ancient Greek mythology, Chiron is the name of a centaur (horse man). All cosmic bodies similar to Chiron were combined into a class centaurs. Today, more than a hundred centaurs are known. All of them move between the orbits of Jupiter and Neptune.
Damocloids- small cosmic bodies revolving around the Sun in orbits similar to comets (strongly elongated and strongly inclined to the plane of the Earth's orbit), but not showing cometary activity (not giving coma and not forming tails). The largest damocloid has a diameter of 72 km, and just over 40 such objects have been discovered to date. Damocloids are one of the darkest bodies in the solar system. It is believed that damocloids are the nuclei of comets that originated in the Oort cloud, but lost their volatile substances. Some damocloids revolve around the Sun in the opposite direction to the movement of the major planets.
Planets of the solar system
According to the official position of the International astronomical union(IAS), an organization that assigns names to astronomical objects, there are only 8 planets.
Pluto was removed from the category of planets in 2006. because in the Kuiper belt are objects that are larger / or equal in size to Pluto. Therefore, even if it is taken as a full-fledged celestial body, then it is necessary to add Eris to this category, which has almost the same size with Pluto.
As defined by MAC, there are 8 known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
All planets are divided into two categories depending on their physical characteristics: terrestrial and gas giants.
Schematic representation of the location of the planets
terrestrial planets
Mercury
The smallest planet in the solar system has a radius of only 2440 km. The period of revolution around the Sun, for ease of understanding, equated to the earth's year, is 88 days, while Mercury has time to complete a revolution around its own axis only one and a half times. Thus, its day lasts approximately 59 Earth days. For a long time it was believed that this planet was always turned to the Sun by the same side, since the periods of its visibility from the Earth were repeated with a frequency approximately equal to four Mercury days. This misconception was dispelled with the advent of the possibility of using radar research and conducting continuous observations using space stations. The orbit of Mercury is one of the most unstable; not only the speed of movement and its distance from the Sun change, but also the position itself. Anyone interested can observe this effect.
Mercury in color, as seen by the MESSENGER spacecraft
Mercury's proximity to the Sun has caused it to experience the largest temperature fluctuations of any of the planets in our system. The average daytime temperature is about 350 degrees Celsius, and the nighttime temperature is -170 °C. Sodium, oxygen, helium, potassium, hydrogen and argon have been identified in the atmosphere. There is a theory that it was previously a satellite of Venus, but so far this remains unproven. It has no satellites of its own.
Venus
The second planet from the Sun, the atmosphere of which is almost entirely composed of carbon dioxide. It is often called the Morning Star and the Evening Star, because it is the first of the stars to become visible after sunset, just as before dawn it continues to be visible even when all other stars have disappeared from view. The percentage of carbon dioxide in the atmosphere is 96%, there is relatively little nitrogen in it - almost 4%, and water vapor and oxygen are present in very small amounts.
Venus in the UV spectrum
Such an atmosphere creates a greenhouse effect, the temperature on the surface because of this is even higher than that of Mercury and reaches 475 ° C. Considered the slowest, the Venusian day lasts 243 Earth days, which is almost equal to a year on Venus - 225 Earth days. Many call it the sister of the Earth because of the mass and radius, the values of which are very close to the earth's indicators. The radius of Venus is 6052 km (0.85% of the earth). There are no satellites, like Mercury.
The third planet from the Sun and the only one in our system where there is liquid water on the surface, without which life on the planet could not develop. At least life as we know it. The radius of the Earth is 6371 km and, unlike the rest of the celestial bodies in our system, more than 70% of its surface is covered with water. The rest of the space is occupied by the continents. Another feature of the Earth is the tectonic plates hidden under the planet's mantle. At the same time, they are able to move, albeit at a very low speed, which over time causes a change in the landscape. The speed of the planet moving along it is 29-30 km / s.
Our planet from space
One revolution around its axis takes almost 24 hours, and full walkthrough the orbit lasts 365 days, which is much longer in comparison with the nearest neighboring planets. The Earth day and year are also taken as a standard, but this is done only for the convenience of perceiving time intervals on other planets. The Earth has one natural satellite, the Moon.
Mars
The fourth planet from the Sun, known for its rarefied atmosphere. Since 1960, Mars has been actively explored by scientists from several countries, including the USSR and the USA. Not all research programs have been successful, but water found in some areas suggests that primitive life exists on Mars, or existed in the past.
The brightness of this planet allows you to see it from Earth without any instruments. Moreover, once every 15-17 years, during the Opposition, it becomes the brightest object in the sky, eclipsing even Jupiter and Venus.
The radius is almost half that of the earth and is 3390 km, but the year is much longer - 687 days. He has 2 satellites - Phobos and Deimos .
Visual model of the solar system
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Sun
The sun is a star, which is a hot ball of hot gases at the center of our solar system. Its influence extends far beyond the orbits of Neptune and Pluto. Without the Sun and its intense energy and heat, there would be no life on Earth. There are billions of stars, like our Sun, scattered throughout the Milky Way galaxy.
Mercury
Sun-scorched Mercury is only slightly larger than Earth's moon. Like the Moon, Mercury is practically devoid of an atmosphere and cannot smooth out the traces of impact from the fall of meteorites, therefore, like the Moon, it is covered with craters. The day side of Mercury is very hot on the Sun, and on the night side the temperature drops hundreds of degrees below zero. In the craters of Mercury, which are located at the poles, there is ice. Mercury makes one revolution around the Sun in 88 days.
Venus
Venus is a world of monstrous heat (even more than on Mercury) and volcanic activity. Similar in structure and size to Earth, Venus is covered in a thick and toxic atmosphere that creates a strong greenhouse effect. This scorched world is hot enough to melt lead. Radar images through the mighty atmosphere revealed volcanoes and deformed mountains. Venus rotates in the opposite direction from the rotation of most planets.
Earth is an ocean planet. Our home, with its abundance of water and life, makes it unique in our solar system. Other planets, including several moons, also have ice deposits, atmospheres, seasons, and even weather, but only on Earth did all these components come together in such a way that life became possible.
Mars
Although details of the surface of Mars are difficult to see from Earth, telescope observations show that Mars has seasons and white spots at the poles. For decades, people have assumed that the bright and dark areas on Mars are patches of vegetation and that Mars might be a suitable place for life, and that water exists in the polar caps. When the Mariner 4 spacecraft flew by Mars in 1965, many of the scientists were shocked to see pictures of the bleak, cratered planet. Mars turned out to be a dead planet. More recent missions, however, have revealed that Mars holds many mysteries that have yet to be solved.
Jupiter
Jupiter is the most massive planet in our solar system, has four large moons and many small moons. Jupiter forms a kind of miniature solar system. To turn into a full-fledged star, Jupiter had to become 80 times more massive.
Saturn
Saturn is the most distant of the five planets that were known before the invention of the telescope. Like Jupiter, Saturn is made up mostly of hydrogen and helium. Its volume is 755 times that of the Earth. Winds in its atmosphere reach speeds of 500 meters per second. These fast winds, combined with heat rising from the planet's interior, cause the yellow and golden streaks we see in the atmosphere.
Uranus
The first planet found with a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet is so far from the Sun that one revolution around the Sun takes 84 years.
Neptune
Nearly 4.5 billion kilometers from the Sun, distant Neptune rotates. It takes 165 years to complete one revolution around the Sun. It is invisible to the naked eye due to its vast distance from Earth. Interestingly, its unusual elliptical orbit intersects with the orbit of the dwarf planet Pluto, which is why Pluto is inside Neptune's orbit for about 20 out of 248 years during which it makes one revolution around the Sun.
Pluto
Tiny, cold and incredibly distant, Pluto was discovered in 1930 and has long been considered the ninth planet. But after the discovery of Pluto-like worlds even further away, Pluto was reclassified as a dwarf planet in 2006.
The planets are giants
There are four gas giants located beyond the orbit of Mars: Jupiter, Saturn, Uranus, Neptune. They are in the outer solar system. They differ in their massiveness and gas composition.
planets solar system, not to scale
Jupiter
The fifth planet from the Sun and the largest planet in our system. Its radius is 69912 km, it is 19 times more earth and only 10 times smaller than the Sun. A year on Jupiter is not the longest in the solar system, lasting 4333 Earth days (incomplete 12 years). His own day has a duration of about 10 Earth hours. The exact composition of the planet's surface has not yet been determined, but it is known that krypton, argon and xenon are present on Jupiter in much larger quantities than on the Sun.
There is an opinion that one of the four gas giants is actually a failed star. In favor of this theory speaks the most a large number of Jupiter has a lot of satellites - as many as 67. To imagine their behavior in the orbit of the planet, a fairly accurate and clear model of the solar system is needed. The largest of them are Callisto, Ganymede, Io and Europa. At the same time, Ganymede is the largest satellite of the planets in the entire solar system, its radius is 2634 km, which is 8% larger than the size of Mercury, the smallest planet in our system. Io has the distinction of being one of only three moons with an atmosphere.
Saturn
The second largest planet and the sixth largest in the solar system. In comparison with other planets, the composition is most similar to the Sun chemical elements. The surface radius is 57,350 km, the year is 10,759 days (almost 30 Earth years). A day here lasts a little longer than on Jupiter - 10.5 Earth hours. In terms of the number of satellites, it is not far behind its neighbor - 62 versus 67. The largest satellite of Saturn is Titan, just like Io, which is distinguished by the presence of an atmosphere. Slightly smaller than it, but no less famous for this - Enceladus, Rhea, Dione, Tethys, Iapetus and Mimas. It is these satellites that are the objects for the most frequent observation, and therefore we can say that they are the most studied in comparison with the rest.
For a long time, the rings on Saturn were considered a unique phenomenon, inherent only to him. Only recently it was found that all gas giants have rings, but the rest are not so clearly visible. Their origin has not yet been established, although there are several hypotheses about how they appeared. In addition, it was recently discovered that Rhea, one of the satellites of the sixth planet, also has some kind of rings.
Comets are the most efficient celestial bodies in the solar system. Comets are a kind of cosmic icebergs, consisting of frozen gases, complex chemical composition, water ice and refractory mineral matter in the form of dust and larger fragments.
Although comets, like asteroids, move around the Sun in conical curves, they look strikingly different from asteroids. If asteroids shine by reflected sunlight and in the field of view of the telescope resemble slowly moving faint stars, then comets intensively scatter sunlight in some of the most characteristic parts of the spectrum for comets, and therefore many comets are visible to the naked eye, although the diameters of their nuclei rarely exceed 1 - 5 km .
Comets are of interest to many scientists: astronomers, physicists, chemists, biologists, gas dynamics, historians, etc. And this is natural. After all, comets suggested to scientists that the solar wind blows in interplanetary space; perhaps comets are the "culprits" of the emergence of life on Earth, as they could bring complex organic compounds into the Earth's atmosphere. In addition, comets, apparently, carry valuable information about the initial stages of the protoplanetary cloud, from which the Sun and planets also formed.
At the first acquaintance with a bright comet, it may seem that the tail is the most main part comets. But if in the etymology of the word "comet" the tail appeared main reason for such a name, then from a physical point of view, the tail is a secondary formation that developed from a rather tiny nucleus - the most important part of the comet as a physical object.
Comet nuclei are the root cause of the rest of the complex of cometary phenomena, which are still not accessible to telescopic observations, since they are veiled by the luminous matter surrounding them, continuously flowing from the nuclei. Using high magnifications, one can look into the deeper layers of the gas-dust shell glowing around the nucleus, but what remains will still significantly exceed the true dimensions of the nucleus in size. The central cluster, visible in the diffuse atmosphere of a comet visually and in photographs, is called the photometric nucleus. It is believed that in its center is the actual nucleus of the comet, i.e., the center of mass of the comet is located.
The foggy atmosphere surrounding the photometric core and gradually fading away, merging with the sky background, is called a coma. The coma together with the nucleus make up the head of the comet. Away from the Sun, the head looks symmetrical, but as it approaches the Sun, it gradually becomes oval, then the head lengthens even more, and a tail develops from it on the side opposite the Sun.
So, the nucleus is the most important part of a comet. However, there is still no consensus on what it actually is. Even in the time of Bessel and Laplace, there was an idea of the comet's nucleus as a solid body, consisting of easily evaporating substances such as ice or snow, which quickly pass into the gas phase under the influence of solar heat. This icy classical model of the cometary nucleus has been significantly expanded and developed in recent times.
Whipple's model of the nucleus, a conglomerate of refractory stony particles and frozen volatile components (CH4, CO2, H2O, etc.), enjoys the greatest recognition among comet researchers. In such a core, ice layers of frozen gases alternate with dust layers. As the solar heat warms, gases like evaporating "dry ice" break through, dragging clouds of dust with them. This makes it possible, for example, to explain the formation of gas and dust tails in comets, as well as the ability of small nuclei of comets to actively release gases.
Comet heads take on a variety of shapes as comets orbit. Away from the Sun, the heads of comets are round, which is explained by the weak effect of solar radiation on the particles of the head, and its outlines are determined by the isotropic expansion of cometary gas into interplanetary space. They are tailless comets that look like globular star clusters. Approaching the Sun, the comet's head takes the form of a parabola or catenary. The parabolic shape of the head is explained by the "fountain" mechanism. The formation of heads in the form of a catenary is associated with the plasma nature of the cometary atmosphere and the impact of the solar wind on it and with the magnetic field carried by it.
Sometimes the comet's head is so small that the comet's tail appears to emerge directly from the nucleus. In addition to changing the outlines, various structural formations appear and disappear in the heads of comets: tacks, shells, rays, outpourings from the nucleus, etc.
Large comets with tails stretching far across the sky have been observed since ancient times. Comets were once thought to be atmospheric phenomena. This misconception was refuted by Brahe, who found that the comet of 1577 occupied the same position among the stars when observed from different points, and, therefore, is farther from us than the Moon.
The movement of comets across the sky was first explained by Halley (1705), who found that their orbits were close to parabolas. He determined the orbits of 24 bright comets, and it turned out that the comets of 1531 and 1682. have very similar orbits. From this, Halley concluded that this is the same comet that moves around the Sun in a very elongated ellipse with a period of about 76 years. Halley predicted that it would reappear in 1758, and in December 1758 it was indeed discovered. Halley himself did not live to see this time and could not see how brilliantly his prediction was confirmed. This comet (one of the brightest) was named Halley's comet.
Comets are named after the names of the people who discovered them. In addition, a newly discovered comet is assigned a provisional designation for the year of discovery, with the addition of a letter indicating the comet's sequence of passage through perihelion in that year.
Only a small part of the comets observed annually are periodic, that is, known from their previous appearances. Most comets move in very elongated ellipses, almost parabolas. Their periods of revolution are not exactly known, but there is reason to believe that they reach many millions of years. Such comets move away from the Sun at distances comparable to interstellar ones. The planes of their almost parabolic orbits do not concentrate to the plane of the ecliptic and are randomly distributed in space. The forward direction of movement occurs just as often as the reverse.
Periodic comets move in less elongated elliptical orbits and have very different characteristics. Of the 40 comets observed more than once, 35 have orbits inclined by less than 45° to the plane of the ecliptic. Only Halley's comet has an orbit with an inclination greater than 90°, and therefore moves in the opposite direction.
Among short-period (i.e., having periods of 3-10 years) comets, the "Jupiter family" stands out - a large group of comets whose aphelia are at the same distance from the Sun as the orbit of Jupiter. It is assumed that the "family of Jupiter" was formed as a result of the capture of comets by the planet, which previously moved in more elongated orbits. Depending on the relative position Jupiter and a comet, the eccentricity of a comet's orbit can either increase or decrease.
In the first case, there is an increase in the period or even a transition to a hyperbolic orbit and the loss of the comet by the Solar System, in the second, a decrease in the period.
The orbits of periodic comets are subject to very noticeable changes. Sometimes a comet passes near the Earth several times, and then, by the attraction of the giant planets, it is thrown into a more distant orbit and becomes unobservable. In other cases, on the contrary, a comet that has never been observed before becomes visible due to the fact that it passed near Jupiter or Saturn and changed its orbit dramatically. In addition to such abrupt changes, known only for a limited number of objects, the orbits of all comets experience gradual changes.
Orbital changes are not the only possible reason for the disappearance of comets. It has been reliably established that comets are rapidly destroyed. The brightness of short-period comets weakens with time, and in some cases the destruction process was observed almost directly.
Bielly's comet is a classic example. It was discovered in 1772 and observed in 1813, 1826 and 1832. In 1845, the size of the comet turned out to be increased, and in January 1846, observers were surprised to find two very close comets instead of one. The relative motions of both comets were calculated, and it turned out that Bieli's comet had split into two about a year ago, but at first the components were projected one on top of the other, and the separation was not immediately noticed. Comet Bieli was observed once more, with one component much weaker than the other, and it was not possible to find it again. On the other hand, a meteor shower was repeatedly observed, the orbit of which coincided with the orbit of Biel's comet.
When solving the question of the origin of comets, one cannot do without knowing the chemical composition of the substance from which the cometary nucleus is composed. It would seem, what could be easier? We need to photograph more spectra of comets, decipher them - and the chemical composition of cometary nuclei will immediately become known to us.
However, the matter is not as simple as it seems at first glance. The spectrum of the photometric nucleus can simply be the reflected solar or molecular emission spectrum. The reflected solar spectrum is continuous and tells nothing about chemical composition the area from which it was reflected - the core or the dusty atmosphere surrounding the core.
The emission gas spectrum carries information about the chemical composition of the gaseous atmosphere surrounding the nucleus, and also does not tell us anything about the chemical composition of the surface layer of the nucleus, since molecules emitting in the visible region, such as C2, CN, CH, MH, OH, etc., are secondary, daughter molecules - "fragments" of more complex molecules or molecular complexes that make up the cometary nucleus. These complex parent molecules, evaporating into the circumnuclear space, are quickly subjected to the destructive action of the solar wind and photons, or decay or dissociate into more simple molecules, whose emission spectra can be observed from comets. The parent molecules themselves give a continuous spectrum.
The first to observe and describe the spectrum of the comet's head was the Italian Donati. Against the background of the faint continuous spectrum of the comet of 1864, he saw three wide luminous bands: blue, green and yellow. As it turned out, this confluence belonged to C2 carbon molecules, which found themselves in abundance in the cometary atmosphere. These emission bands of C2 molecules are called Swan bands, after the scientist who studied the spectrum of carbon. The first slit spectrogram of the head of the Great Comet in 1881 was obtained by the Englishman Heggins, who detected the radiation of the chemically active cyanide radical CN in the spectrum.
Far from the Sun, at a distance of 11 AU. That is, the approaching comet looks like a small hazy speck, sometimes with signs of the beginning formation of a tail. The spectrum obtained from a comet located at such a distance, up to a distance of 3 - 4 AU. That is, it is continuous, because at such large distances the emission spectrum is not excited due to weak photon and corpuscular solar radiation.
This spectrum is formed as a result of reflection sunlight from dust particles or as a result of its scattering on polyatomic molecules or molecular complexes.
At a distance of about 3 a. i.e. from the Sun, i.e. when the cometary nucleus crosses the asteroid belt, the first emission band of the cyanide molecule appears in the spectrum, which is observed in almost the entire head of the comet. At a distance of 2 a. i.e., radiation of triatomic C3 and NH3 molecules is already excited, which are observed in more limited area comet heads near the nucleus than all the intensifying CN emissions. At a distance of 1.8 a. That is, carbon emissions appear - Swan bands, which immediately become noticeable in the entire head of the comet: both near the nucleus and at the boundaries of the visible head.
The mechanism of the glow of cometary molecules was deciphered as early as 1911 by K. Schwarzschild and E. Kron, who, studying the emission spectra of Halley's comet (1910), came to the conclusion that the molecules of cometary atmospheres resonantly re-emit sunlight.
This glow is similar to the resonant glow of sodium vapor in the well-known experiments of Aud, who was the first to notice that when illuminated with light having the frequency of a yellow sodium doublet, sodium vapor itself begins to glow at the same frequency with a characteristic yellow light.
This is the resonant fluorescence mechanism, which is a frequent case of the more general luminescence mechanism.
Everyone knows the glow of fluorescent lamps over shop windows, in lamps daylight etc. A similar mechanism causes the gases in comets to glow.
To explain the glow of the green and red oxygen lines (similar lines are also observed in the spectra of auroras), we used various mechanisms: electron impact, dissociative recombination and photodissociation. Electron impact, however, fails to explain the higher intensity of the green line in some comets compared to the red line.
Therefore, more preference is given to the photodissociation mechanism, which is supported by the brightness distribution in the comet's head.
However, this issue has not yet been finally resolved, and the search for the true mechanism of the glow of atoms in comets continues.
Until now, the question of the parent, primary molecules that make up the cometary nucleus remains unresolved, and this issue is very important, since it is the chemistry of the nuclei that predetermines the unusually high activity of comets, capable of developing giant atmospheres and tails from very small nuclei, exceeding in size all known bodies in the solar system to their size.
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 Entrance door Earth would be the size of a dime, the dwarf planet Pluto would be the size of a pinhead, and the largest Kuiper Belt comet (which is about 100 km across, about one-twentieth of Pluto) would be the size of a grain 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 periodic comet. 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 (thought to have been a single comet at the time) came close to Jupiter in July 1992 and was tidally crushed 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
"Freight train" of fragments crashed on Jupiter with a 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 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. The original orbit of this comet passed 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 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 accompany 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 radiate about twice more quantity gas dust. 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 probably protect the rovers on the surface, but a spacecraft in orbit will be under massive fire from 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 a way that interferes with the vehicles' ability to generate power and communicate with the Earth. “These changes will require great amount 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 further 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 influence - perhaps from passing by a star - pushes the comet free from its incredibly huge 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 is, more than twice over size 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 Leonid 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 aid, 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 showed a further slowdown, 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 rate of increase in brightness has decreased, and magnitude at perihelion was predicted as +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.
Of all the comets, perhaps the most famous is Halley's Comet. It appears in the sky every 75.5 years, moving in an elongated elliptical orbit around the Sun.
Starting from 239 BC. e., that is, since the appearance of Halley's comet is recorded in historical chronicles, it has been observed 30 times. This is due to the fact that it is much larger and much more active than other periodic comets.
The comet, as is easy to understand, is named after the English astronomer and physicist Edmund Halley (1656-1742), although he was not its discoverer. But it was Halley who was the first to discover in 1705 a connection between the comet he observed in 1682 and a number of other comets, the appearance of which was officially registered with an interval of 76 years.
Moreover, based on Isaac Newton's law of universal gravitation, the scientist was also able to calculate the orbits of some planets. From these calculations it followed that the orbits of the comets that were seen in 1531, 1607 and 1682 are largely similar. And based on these data, Halley predicted that the comet would reappear in 1758-1759. The scientist's prediction came true, but after his death.
The perihelion of the orbit of Halley's Comet lies between the orbits of Mercury and Venus at a distance of 0.587 AU. e. The farthest point of its trajectory is located outside the orbit of Neptune at a distance of 35.31 AU. e. The orbit is inclined to the main plane of the solar system by 162°, and the comet orbits in the opposite direction to the motion of the planets.
In 1986, Halley's comet approached our planet again. But due to meteorological conditions, it was very difficult to observe it from Earth. However, space probes sent by a number of countries have conducted a fairly successful study of the comet.
As a result of the research, it was finally proved that the comet has a solid core, consisting of ice and dust. Him elongated shape. The length of the core is 14 kilometers, and almost the same height and width - 7.5 kilometers each. It slowly rotates, making one revolution in 7.1 days.
The nucleus of Halley's comet is very dark, so it reflects only 4% of the incident sunlight. Due to the fact that on the side facing the Sun the temperature reached almost 100 degrees Celsius, emissions of gas and dust were also noted.
When any comet is on minimum distance from the Sun, its core is destroyed. At the same time, the gases that evaporate from the surface of the comet also carry along individual particles of various sizes.
And if microscopic dust particles are “pushed” into the tail under the action of sunlight pressure, then light pressure has no effect on large particles. In this case, dust particles and particles that have come off the surface of the cometary nucleus move along with it along the orbit of the comet. And after some time they fill a certain elliptical torus with the orbit of this comet as its axis. And since Halley's comet has been moving in its current orbit for over a hundred thousand years, it means that the swarm of dust particles on it closed a long time ago. True, this accumulation of "cosmic dust" consists not only of dust particles, but also fragments of cometary matter ranging in size from grains of sand to fragments and blocks, weighing several kilograms or tons, respectively.
There are two known meteor showers associated with Halley's comet: the Aquarids, observed in May, and the Ori onids, observed in October.
Observations of the movement of these swarms of particles have established that the modern meteors of the Aquarid and Orionid streams are generated by those particles that were ejected from a comet several millennia ago.
In turn, the analysis of data on the fall of meteorites from 1800 to the present day revealed the periodicity of these events. Moreover, this information contains data on periods equal to approximately 75 years. And this figure is very close to the average period of revolution in its orbit of Halley's comet.
Astronomers explain this periodicity in the frequency of meteorite falls by the fact that cometary nuclei consist of many separate bodies, which, under the influence of the Sun's gravity, come off one after another ...
Let us note one more curious fact connected with Halley's comet. So, it is believed that its core is monolithic. However, during the passage of Halley's comet near the Earth in 1910, many observers noted phenomena that testify to the fragmentation of its nucleus.
So, it was noticed that the nucleus of the comet consisted of several bright formations, which disappeared rather quickly. Then the nucleus of Halley's comet again found itself alone, then again crushed.
In addition to Halley's comet, some tailed celestial objects have gained considerable popularity among astronomers.
For example, Biel's comet is known for splitting into two before completely disappearing. It was discovered in 1772. When she was seen again on February 27, 1826, astronomers were able to accurately calculate her orbit. And then, based on these data, it was found that its period is 6.6 years.
When the comet appeared in 1846, it had already been divided into two parts. And after another 6.6 years, the two halves were at a distance of more than two million kilometers, but moved in the same orbit. The two bodies were never seen after that.
Comet Shoemaker-Levy became widely known for crashing into the planet Jupiter in July 1994. When it was first photographed on March 25, 1993, it was in orbit around Jupiter with a 2-year orbital period and was a chain consisting of about 20 separate fragments.
Mathematical models have shown that this comet has been orbiting Jupiter for several decades. But then, under the influence of tidal forces, during a close approach to Jupiter in July 1992, it separated. This meeting also caused a change in the trajectories of its fragments, leading them to collide with the planet.
They collided with Jupiter one by one between July 16 and 22, 1994. As a result of this catastrophe, large dark clouds appeared in the atmosphere of Jupiter, which did not disappear for several months. In infrared light, bright flashes were also visible ...
