Project diversity of nature of the Kirov region. Kirov and Kirov region: history, nature, climate
Pluto was discovered in 1930. But 76 years later, the IAU deprived this object of the right to be called a planet and transferred it to the rank of dwarf planets. It is now believed that Pluto, like Eris, is only one of the largest neptunoids inhabiting the Kuiper Belt.
And in 1978, its main satellite, Charon, was identified. It was discovered while studying photographic plates depicting Pluto. On one of the plates, a hump appeared on the planet, which turned out to be a planet when examined.
Charon was originally named a satellite of Pluto, but now it is believed to be a double planet. Their common center of gravity is located outside the main planet. This is a unique type of interaction. It is also unusual that they always face their counterparts with the same side.
But it's not actually confirmed yet...
Double planet is a term in astronomy used to refer to a binary system consisting of two astronomical objects, each of which meets the definition of a planet and is massive enough to exert a gravitational effect greater than that of the star around which they orbit.
As of 2010, there are officially no systems in the Solar System classified as "double planets". One of the unofficial requirements is that both planets orbit a common center of mass, also called a barycenter, which must be above the surface of these planets.
Charon's diameter is 1205 km - slightly more than half that of Plutonian, and their masses have a ratio of 1:8. This is the mosta large satellite in the solar system in comparison with its planet. The distance between the objects is very small - 19.6 thousand km, and the satellite's orbital period is about a week.
From 1985 to 1990, a rather infrequent phenomenon was observed: eclipses. They alternated: at first one planet eclipsed the other, then vice versa. Such eclipses have a cycle of 124 years.
Analysis of the reflected light allows us to conclude that there is a layer of water ice on the surface of Charon, in contrast to the methane-nitrogen layer of Pluto. According to the Gemini Observatory, ammonia hydrate and water crystals were found on Charon. This makes the existence of cryogeysers likely.
The unusual, in comparison with other planets of the Solar System, parameters of the orbits of the planetary pair and their modest sizes give rise to scientists’ hypotheses about their origin. It is believed that the planets formed in the Kuiper belt, and were torn out from there by the gravity of the giant planets.
Another hypothesis suggests the formation of the system after the collision of the already existing Pluto with the proto-Charon. The current satellite was formed from the ejected debris. And now they are together, Pluto and Charon - the distant outskirts of the solar system.
As mentioned above, the Pluto-Charon system meets the definition of a double planet. At the moment, these are the only bodies in the Solar System that can claim such a status.
According to draft Resolution 5 of the XXVI General Assembly of the IAU (2006), Charon was supposed to be given the status of a planet. The notes to the draft resolution indicated that in this case Pluto-Charon would be considered a double planet. The basis for this was the fact that each of the objects can be considered a dwarf planet, and their common center of mass lies in open space. However, at the same assembly, the IAU introduced a definition of the concepts of “Planet” and “Dwarf Planet”. According to the introduced definitions, Pluto is classified as a dwarf planet, and Charon is its satellite, although this decision may be revised in the future
As the New Horizons spacecraft continues its journey to the outer edge of the Solar System, its target - which lies in the Kuiper Belt - becomes brighter and clearer. New images from the Long Range Reconnaissance Imager (LORRI) clearly show Pluto and its largest moon, Charon, locked in a tight orbital dance. The two objects are separated by a distance of just over 18,000 kilometers.
These images, which show Charon orbiting Pluto, are record-breaking in terms of the distance from which they were taken: 10 times less than the distance from Pluto to Earth.
We've already seen images of Pluto and Charon, but there's something else to see in this animation.
Over 5 days, LORRI took 12 images of the Pluto-Charon system, during which time Charon almost completely completed 1 revolution around Pluto. However, as Charon orbits, distinct fluctuations in Pluto's position can be observed. Charon's mass (about 12 percent of Pluto's mass) exerts a strong gravitational influence on Pluto, pulling it very distinctly "away from the center." Therefore, both objects orbit an imaginary point above Pluto's surface. This point is called the center of gravity of the Pluto-Charon system.
Comparative sizes of trans-Neptunian objects compared to Earth.
This is a completely atypical situation for the planets of the Solar System - only binary asteroid systems can have barycenters (centers of gravity) outside the objects themselves. As a result, many scientists have come to the conclusion that Charon should be recognized as an independent planet, or the Pluto-Charon system should be designated as a double planet.
In 2012, a paper was published indicating that Pluto's four other moons do not actually orbit it. They follow an orbit around the center of gravity of the Pluto-Charon system, that is, they are satellites of Pluto and Charon, and not just Pluto!
However, the international organization that deals with the classification of celestial objects should once again investigate this fact. The International Astronomical Union will likely need to re-examine the Pluto-Charon system, especially after close-up images are obtained next year.
- The dwarf planet Pluto is named after the Roman god of the underworld. In Roman mythology, Pluto was the son of Saturn, who with his three brothers ruled the world: Jupiter controlled the sky, Neptune was the ruler of the seas, and Pluto ruled the underworld.
- Pluto's atmosphere is composed of nitrogen with some methane and carbon monoxide.
- Pluto is the only known dwarf planet to have an atmosphere. Pluto's atmosphere is unsuitable for human breathing and has a low altitude. When Pluto is at perihelion (closest to the sun), its atmosphere becomes gaseous. When Pluto is at apohelia (farthest from the sun), its atmosphere freezes and precipitates onto the planet's surface.
- It takes Pluto 248 Earth years to complete a revolution around the sun. This is the longest period of orbit around the center of our system of all the planets. The fastest of the planets in this regard is Mercury, which takes 88 Earth days to complete a revolution around the sun.
- It takes Pluto 6 days, 9 hours and 17 minutes to rotate once around its own axis, making it the second slowest rotating planet in the solar system. Only Venus rotates the slowest around its axis – in 243 Earth days. Jupiter, although the largest of the planets, rotates at a rate of one revolution in less than 10 Earth hours.
- Pluto rotates in the opposite direction to the Earth's rotation. This means that the sun there rises in the west and sets in the east. Only Venus, Uranus and Pluto rotate opposite to the earth's.
- Because Pluto's moon Charon is only slightly smaller than the planet itself, astronomers call them together a double planet.
- Sunlight takes five hours to reach Pluto, but it takes only eight minutes for a sunbeam to reach Earth's surface.
- In astrology, Pluto is associated with both beginning (rebirth) and destruction (death).
- When Pluto was one of the planets of the solar system (now it is classified as a minor planet), it was considered the coldest of them. Its temperature ranges from -240° to -218° C. The average temperature here is -229° C. The lowest temperature recorded on Earth was recorded in Antarctica and was equal to -89.2° C, and our planet was the hottest (up to 70.7°) in the Iranian desert of Lut.
- A person weighing 45 kg on Earth will weigh about 2 kg 750 g on Pluto.
- Pluto is so dark that a person would be able to admire the stars from its surface all day.
- Trying to see Pluto from Earth is like trying to see a walnut from a distance of 50 kilometers.
- Since the satellite Charon and Pluto itself rotate mutually around each other, from the surface of Pluto Charon appears frozen motionless in the sky. In addition, the same sides of Pluto and Charon are constantly directed towards each other.
- Pluto has four moons: Charon (named after the ferryman of hell), Nyx (after the Greek goddess of night and darkness), Hydra (named after the nine-headed snake that guards hell) and the as-yet unnamed moon S/2011 P 1, which was discovered quite recently (in 2011).
- No artificial flying object launched from Earth has ever visited Pluto. However, the New Horizons probe, launched in 2006, is scheduled to fly by Pluto in 2015.
- For 76 years, Pluto was considered a planet. However, when astronomers discovered that it was one of many large objects within the Kuyper belt, Pluto has been called a "dwarf planet" since 2006.
- Pluto is the second largest dwarf planet in the solar system. Only Eris is larger than it, which is 27% larger than Pluto.
- Pluto is smaller than Mercury and seven other moons of various planets, including Ganymede, Titan, Callisto, Io, Triton and our Moon.
- When Pluto was discovered in 1930, many people proposed different names for it. The options were: Chronus, Persephone, Erebus, Atlas and Prometheus. Eleven-year-old Venetia Bernie suggested the name Pluto. She thought it would be a good name since the planet was so dark and so far away, as was the god of the underworld. On May 1, 1930, the name of the planet was officially assigned, and the girl received a reward of five pounds sterling.
- Many scientists believe that if Pluto were closer to the sun, it would be classified as a planet.
- Pluto's official name is now "asteroid number 134340." It was so named after being excluded from the planets of the solar system and being relegated to the rank of “dwarf planets”. (Dwarf planets are designated as asteroids in astronomical catalogs).
- While Pluto has been demoted to a dwarf planet, many scientists are trying to classify it and several of its fellow planets again, since they have their own atmosphere, seasons, polar caps and their own moons.
- Sunlight on Pluto is 2,000 times dimmer than on Earth, and from its surface the sun will only appear as a small dot in the sky.
- The official symbol of Pluto is the intertwined letters "P" and "L", which not only symbolize the name, but are also the initials of Percival Lowell, an American astronomer who initiated the search for a planet that was supposed to be located further than Neptune, which led to the discovery of Neptune. One of the observatories in the US state of Arizona is named after Lowell.
- On Pluto, the sun rises and sets about once a week.
Pluto is the largest dwarf planet in the solar system. It was discovered in 1930, but 76 years later the IAU deprived this object of the right to be called a planet and transferred it to the rank of dwarf planets. It is now believed that Pluto, like Eris, is only one of the largest objects inhabiting.
And in 1978, its main satellite, Charon, was identified. It was discovered while studying photographs of Pluto. In one of the photographs, the planet appeared to have a “hump,” which later turned out to be its satellite.
Characteristics of the planet
Orbit
Due to the significant elongation of the orbit, a minor planet is at a distance of 4 to 7 billion km. As a result, Pluto at some moments may be closer to the star than . But Pluto’s orbit has a large inclination to the ecliptic plane, so it does not intersect with Neptune’s orbit. Pluto's rotation axis is tilted like its axis, so it also rotates while lying on its side. The dwarf planet's diameter is two-thirds that of Earth's and its mass is 0.0021. One revolution around the Sun takes 247 years at a speed of 4.666 km/s.
The surface of Pluto is very heterogeneous. This can even be seen in images taken by the Hubble Telescope, and was later confirmed by much better photographs from the New Horizons probe. Spectral data shows that there is water ice on the surface, but it is largely masked by a blanket of more volatile ice.
In 2015, using images from the New Horizons spacecraft, a vast bright zone in the shape of a heart symbol measuring 1800x1500 km was discovered on Pluto.
In the equatorial zone there are 3.5-kilometer mountains rising sharply above the generally smoothed ice surface, presumably consisting of water ice. The most notable geological feature discovered on Pluto is Sputnik Planitia. This depression is more than 1000 km in size - probably a heavily destroyed impact crater. It is filled with frozen gases and intersected by many grooves that divide it into cells tens of kilometers in size.
Internal structure
Supposedly, Pluto consists of three parts. Core of silicate minerals and water ice. The middle part, the mantle, is water ice. The outer shell is frozen nitrogen.
Probable structure of Pluto. 1. Frozen nitrogen 2. Water ice 3. Silicates and water ice
In size and mass, Pluto is the smallest of all the planets in the solar system. It also did not surpass seven more satellites of other planets. It was bypassed by Ganymede, Titan, Callisto, and.
Charon - moon of Pluto
Charon's diameter is 1205 km, it is the largest satellite in comparison with its planet. The distance between the objects is very small - 19.6 thousand km, and the period of revolution around Pluto is about a week.
From 1985 to 1990, a rather infrequent phenomenon was observed: eclipses. They alternated: at first one planet eclipsed the other, then vice versa. Such eclipses have a cycle of 124 years.
Analysis of the reflected light allows us to conclude that there is a layer of water ice on the surface of Charon, in contrast to the methane-nitrogen layer of Pluto. According to the Gemini Observatory, ammonia hydrate and water crystals were found on Charon. This makes the existence of cryogeysers likely.
The unusual, in comparison with other planets of the Solar System, parameters of the orbits of the planetary pair and their modest sizes give rise to scientists’ hypotheses about their origin. It is believed that the planets formed in the Kuiper belt, and were torn out from there by the gravity of the giant planets.
Another hypothesis suggests the formation of the system after the collision of the already existing Pluto with the proto-Charon. The current satellite was formed from the ejected debris. And now they are together, Pluto and Charon - the distant outskirts of the solar system.
Satellites
In total, Pluto has five satellites:
- Hydra. It rotates in the Charonian plane at a distance of 65,000 km from Pluto. Diameter is approximately 52 – 160 km.
- Nikta. It is separated from the main planet by 50,000 km, and its approximate diameter is from 32 to 145 km.
- Kerber. The orbit of this satellite lies between the orbits of Hydra and Nikta, and its diameter is determined from 13 to 34 km.
- Styx. The diameter of the smallest satellite is from 10 to 25 km. Its orbit is between the orbits of Charon and Niktas.
- described above.
Research
Pluto and Charon are the most inaccessible and poorly studied objects in the solar system. No space probe has ever been in the vicinity of a double planet. Voyager 1 could have flown nearby, but was redirected to a different trajectory, chosen in favor of Titan's satellite. There are only photographs taken using the Hubble telescope. On July 15, 2015, the New Horizons spacecraft flew past Pluto at a distance of 12.5 thousand km from the surface. For both Pluto and Charon, both the side visible at closest approach and the opposite side were photographed.
Journey to Pluto
If we were on Pluto, we would not be able to admire the rising and setting of its moon, Charon. But no matter how huge it would seem to us in comparison with the Earth’s satellite!
Imagine that ours has grown a hundred times! And it hangs motionless, as if advancing with its entire enormous mass; you can even feel its pressure. And the distant Sun illuminates sparkling nitrogen ice with a dim light.
Pluto's satellite Charon, amazing in its characteristics and mysterious in origin, was considered the only natural satellite of a minor planet in our solar system until 2005, when astronomers found two more celestial bodies orbiting this planet. Charon is located almost twenty thousand kilometers from the planet, its mass is 1.9 sextillion kilograms, and the radius of the planet is approximately 600 km.
Pluto's moon Charon
For many years since the discovery of the satellite Charon, and this is 1978, it was believed that the planet Pluto has only one single satellite. And his discovery occurred thanks to a careful study of photographs of Pluto, where the planet appeared with a small bulge, which turned out to be its satellite passing in front of the planet’s disk. In 1985-1990, Pluto and its satellite Charon entered an eclipse phase, when their orbits, both the planet and its satellite, became visible from the Earth, as if edge-on. This is a rare phenomenon that occurs only 2 times in Pluto’s 248-year revolution around the Sun, so we can say that scientists were very lucky to get into this period, which accurately established the presence of a satellite and its size.
(The picture shows the surface of Pluto and the large satellite Charon in the artist’s imagination)
The satellite, due to its distance from the star, has a low temperature on its surface, it is 53 degrees Kelvin, which translated into degrees Celsius means 220 degrees below zero. Therefore, the entire surface of the satellite is covered with water ice, this will once again make scientists think about the origin of this celestial body. There is an opinion that the satellite has geological activity, which can form liquid on the surface; scientists justify this fact by the fact that ammonia hydrates were identified on the surface, which should have undergone rapid decay due to solar activity.
(The picture shows Pluto and its satellite Charon in the artist’s imagination)
All data obtained through spectral analysis is reliable, but scientists promise to soon provide new parameters of the planet, because by 2015 they will be more involved in research. An interesting fact is that Pluto and Charon orbit at the same time, because of this they are always directed towards each other by the same side.
Small moons of Pluto
The Pluto-Charon system turned out to have smaller brothers and sisters. These are two small satellites S/2005 P1 "Hydra" and S/2005 P2 "Nikta", discovered in 2005, their diameter is no more than 45 - 60 km. Then in 2011, the fourth satellite P4 with a diameter of 13-34 km was discovered, and a year later the fifth smallest satellite P5, with a diameter of only 10-25 km, was added to the family of known satellites of Pluto.
(In this image taken by the Hubble telescope on July 7, 2012, five of Pluto's moons, two of which P4 and P5 are likely to be named Vulcan and Cerberus, received the most votes in an Internet poll conducted by the SETI Institute)
Thus, at present, as of 2013, it is precisely known about 5 satellites of the planet, the last 2 of which will soon receive their names p4 most likely - “name”, and P5 - “” according to information... (source)
Origin of Pluto's moons
(In the 3D modeling, a view from the surface of Pluto, the satellite Charon and its younger sister are clearly visible, most likely the satellite Hydra in the artist’s imagination, and a bright star is visible far, far away - this is the Sun)
The Pluto-Charon system is called so because, by studying very different properties and planets, scientists hypothesized that both objects of the Solar System appeared during a collision during the independent formation of the planet Pluto and its future satellite, that is, the Charon satellite was formed from fragments of the planet. By the way, two other satellites of Pluto, Nix and Hydra, may have been formed from the same fragments. But the origin of Pluto’s other small satellites still remains a mystery, since it is not clear how such small objects can be so close to a fairly large Charon, despite the fact that their circular orbit rejects the assumption that they are captured by Pluto’s gravity.
Scientists believe that if Pluto still has satellites, then their diameter will be no more than 20 km and their appearance is most likely associated with a collision in the distant past, which also does not exclude the possibility of Pluto having a ring from the same fragments.
In the solar system there are planets so small that they are called dwarfs. This includes Pluto. But even small planets have satellites. Her largest companion is Charon. But he is not the only one of his kind. There are others too. They, of course, are not so great, but they are also of great importance.
In this article we will look at the features of Pluto and find out what Charon, the satellite of this planet, is. Let's also talk about the other, smaller satellites.
Planet Pluto
Until 2006, Pluto stood on a par with the main planets of the solar system and was a full-fledged unit.
Now it was given the name dwarf planet, after which they began to believe that it is the largest object in the dark disk-shaped zone.
One day, it became clear to scientists that Pluto is not a unique object in its environment, like all the other planets located in the Solar System. And that more than one such object can be discovered if you explore the space beyond the orbit belonging to Neptune. And soon a certain body was indeed discovered, called Eris. This was which can be compared with Pluto. After this discovery, it became clear that the world, in fact, lacks a definition of a planet. And in 2006, a definition was approved that included three positions. According to him, those that correspond to only two positions out of three are called Pluto.
It got its name from an eleven-year-old girl who decided that the name of the god of the underworld was suitable for a distant, probably cold and dark planet, and told her grandfather about it. And the grandfather already conveyed his granddaughter’s wish to the observatory, where it was finally approved.
In 2006, a spacecraft called New Horizons was launched towards the planet Pluto. It was the month of January. This device flew up to the planet at a distance of twelve thousand kilometers and accumulated a large amount of information about it. All this data is gradually transferred to scientists. This is due to the too slow transmission of information over such long distances.
Features of the planet
Pluto has the shape of a perfect sphere. This discovery came as a surprise, as did the discovery of various landforms on the surface.
Moreover, there are extended areas on the planet that are completely devoid of impact craters. It is also known that Pluto's glaciers are unevenly distributed across its surface, but it is still not clear why.
The satellite Charon, like other small satellites, is quite far removed from the Earth. Therefore, they have not been studied very well. There is an assumption that the surface of this planet has a rocky base, which is covered with water ice, as well as frozen methane and nitrogen. It is the products resulting from the photodissociation of methane that color the planet red.
Rotating in its orbit, which is far from the shape of a circle, Pluto can either get very close to the Sun, or, conversely, move away to a great distance. As it approaches, an atmosphere is formed around the planet, which consists of methane and nitrogen. The further the planet moves away from the Sun, the smaller the atmosphere becomes, and eventually only a small haze remains, which, when viewed with the naked eye, has a red tint. This happens because the glaciers freeze again.
Moons of Pluto. Charon and the planet's small satellites
Pluto has five natural satellites. The largest satellite, Charon, was discovered in 1978. Two smaller moons, named Nikta and Hydra, were spotted in 2005.
Kerber was next. Its discovery occurred thanks to the Hubble telescope in 2011. And finally, in 2012, scientists discovered the presence of a fifth satellite of Pluto, which was named Styx. All the names of the satellites in one way or another refer to the underworld of Greek mythology.
Charon is a satellite of the planet Pluto
Charon got its name in honor of the carrier of the souls of dead people from the myths of Ancient Greece. It was discovered by US astrophysicist James Christie. This happened at the Naval Observatory in 1978.
This satellite is very large. Its size is equal to half the size of Pluto itself. The distance separating him from the planet he is accompanying is almost twenty thousand kilometers. This is approximately the same as from London to Sydney.
Charon is a satellite of Pluto, which many scientists have come to consider as a small component of a binary system of planets. It was even given the name Pluto 1. The rotation periods of Pluto and Charon are the same. Thanks to this phenomenon, they always face each other with the same side. This phenomenon even got its own name - tidal lock.
Surface and composition of the satellite
The satellite Charon differs in its composition from Pluto. Unlike the planet, it is covered not by nitrogen, but by water ice. This is due to the fact that its surface temperature is 220 degrees Celsius below zero. But also the reasons for this composition include the fact that Charon is not so massive as to retain volatile compounds. The color of the satellite is more neutral, grayish. According to the existing theory, Charon was formed from fragments of Pluto itself that found themselves in orbit. Also, many scientists believe that Charon is connected.
Satellite Nikta
Charon is the largest but there are others. One of them is Nikta. The discovery of this satellite was made public in 2005, on October 31. He owes his name to the goddess of eternal night.
The orbit in which the satellite is located is circular. There is no information yet about the exact dimensions of Nikta, but it is presumably smaller than Hydra. This is indicated by the darker color of the surface.
Hydra
If you carefully examine the existing images, you can see that Hydra is located in the same plane as the satellite Charon. The distance between Pluto and Hydra is approximately 65 thousand kilometers. There is no data on the exact size of this satellite. Scientists only assume that its diameter ranges from 52 to 160 kilometers.
Hydra's surface is brighter than Nyx's. By about 25%. This suggests that its reflectivity is higher, which means its dimensions are larger. The satellite received its name in honor of a monster from Greek mythology with a hundred heads.
Kerberos and Styx
Pluto's fourth satellite is named Kerberos, also named after the mythical character of the underworld. Before the discovery of the fifth satellite, it was considered the smallest. Its estimated diameter is 13-34 kilometers.
The discovery of Kerberos was made thanks to the Hubble Space Telescope. The orbit in which the fourth satellite rotates is located between the orbits of Nix and Hydra. It orbits the planet in thirty-one days.
The smallest size is the fifth satellite Styx. Presumably its diameter is between 10 and 25 kilometers. This satellite rotates in an orbit located between the orbits of Charon and Nix. Its resonance with Charon is a ratio of one to three. It owes its name to the river, which in the myths of Ancient Greece separates two worlds - the living and the dead. It was also discovered by Hubble in June 2012.
This article covered many issues. We found out which planet Charon is a satellite of, what are its features, size and composition. Now to the question: “Charon is a satellite of which planet?” - you will confidently answer: “Pluto.” By the way, one of the theories for the emergence of satellites around Pluto says that they were all formed as a result of the collision of this planet with some large object from the Kuiper belt. Unfortunately, today almost nothing more can be learned about these amazing objects. After all, Pluto is not only too far from Earth, but also does not have very good reflectivity.
(6 days 9 hours 17 m 36.7 ± 0.1 s)
Studying
Opening
The discovery of Pluto's first moon by James Christie was published by the International Astronomical Union on July 7, 1978.
After checking the observatory's archives, it turned out that some images of Pluto taken in excellent visibility conditions were also slightly elongated, while images of stars were not. This could be explained by the presence of a satellite of Pluto, located so close to it that the resolution of the telescope was not enough to see them separately.
It is important to note that after the discovery of Charon, the theory that Pluto was once a satellite of Neptune was refuted.
Name
The temporary designation of the open satellite became 1978 P 1. The US Naval Observatory proposed the name "Persephone" - the name of the consort of Hades/Pluto. The discoverer himself, on June 24, 1978, chose the name “Charon” for the satellite in honor of his wife Charlene, who was called “Ball” and the particles “-on”, by analogy with the words “electron”, “neutron” and “ proton". And in English this name coincides with the name of Charon - the carrier of the souls of the dead across the Styx. On January 3, 1986, the IAU approved the name Charon. In English, the satellite is also called "Sharon".
Subsequent studies
Christie researched further and found that these observations could be explained if the satellite's orbital period was 6.387 days, and its maximum angular distance from the planet was approximately 1 arcsecond.
These conclusions were confirmed in the period from February 1985 to October 1990, when extremely rare phenomena were observed from Earth: alternating mutual eclipses of Pluto and Charon. Bringing Earth into Charon's orbital plane to observe these eclipses occurs only twice during Pluto's 248-year orbital period, and fortunately this event occurred shortly after the moon's discovery. Since Charon's orbital period is just under a week, eclipses repeated every three days, and a large series of these events occurred over five years. These eclipses made it possible to produce "brightness maps" and obtain good estimates of the radius of Pluto (1150-1200 km) and Charon.
The first images of Pluto and Charon as separate disks were taken by the Hubble Space Telescope in the 1990s. Later, with the development of adaptive optics, it became possible to see the individual disks of Pluto and Charon using ground-based telescopes.
The Pluto system, including Charon, was studied in detail at close range by the American spacecraft New Horizons in 2015. For Charon, as for Pluto, both the side visible at closest approach and the opposite side were photographed (its images were taken before approach and therefore have a lower resolution). LORRI's excellent sensitivity and angular resolution showed Charon exactly at its predicted position relative to Pluto, 35 years after its discovery by James Christie. The camera captured images of Pluto and Charon at a much higher phase angle (the angle between the Sun, Pluto and the spacecraft) than can be reached from Earth or low-Earth orbit.
Status
Historically, Charon is considered a satellite of Pluto. However, then the opinion spread that since the center of mass of the Pluto-Charon system is located outside Pluto and the rotation of the system is mutually synchronized, Pluto and Charon should be considered as a binary planetary system.
According to draft Resolution 5 of the XXVI IAU General Assembly (2006), Charon, along with Ceres and Eris (formerly known as object 2003 UB 313), was supposed to be given planet status. The notes to the draft resolution indicated that in this case the Pluto-Charon system would be considered a double planet.
However, the final version of the resolution contained a different solution: the concept of “dwarf planet” was introduced. Pluto, Ceres and Eris were assigned to this new class of objects. Charon was not included among the dwarf planets.
Orbit and dimensions
By the mid-1980s, ground-based methods, primarily using speckle interferometry, were able to estimate the radius of Charon's orbit quite accurately; subsequent observations by the Hubble orbital telescope did not change that estimate much, establishing that it was within the range of 19,628 -19,644 km. The orbit is inclined 55° to the ecliptic. One revolution of Charon around Pluto takes 6.387 days, and due to tidal locking, the same period of time is equal to the rotation periods of Charon and Pluto. Therefore, Pluto and Charon are constantly facing each other with the same side; Charon in the sky of Pluto is motionless, just like Pluto in the sky of Charon.
Pluto and Charon are often considered a double planet because their system's barycenter is outside of both objects.
The discovery of Charon allowed astronomers to accurately calculate Pluto's mass. Features of the orbits of the outer satellites show that Charon's mass is approximately 11.65% of Pluto's mass.
Between February 1985 and October 1990, extremely rare events were observed: alternating eclipses of Pluto by Charon and Charon by Pluto. They occur when the ascending or descending branch of Charon's orbit ends up between Pluto and the Sun, and this happens approximately every 124 years. Since Charon's orbital period is just under a week, eclipses occurred approximately every three Earth days, and a large series of these events occurred over five years. These eclipses made it possible to compile "brightness maps" and obtain good estimates of Pluto's radius (1150 -1200 km).
As a result of processing the data transmitted by the New Horizons AMS, by October 16, 2015, an estimate of 1212 ± 6 km was obtained for Charon’s diameter, and for its density - 1.702 ± 0.021 g/cm³.
Surface and composition
Main article: Geology of Charon
Charon is noticeably darker than Pluto. It appears that these objects differ significantly in composition. While Pluto has a lot of nitrogen ice on its surface, Charon is covered in water ice and its surface has a more neutral (less reddish) color. It is currently believed that the Pluto-Charon system was formed as a result of the collision of independently formed Pluto and proto-Charon; modern Charon was formed from fragments thrown into orbit around Pluto; this could also have produced some Kuiper Belt objects.
According to some models, Charon may be geologically active down to the presence of liquid below the surface. This is justified by the fact that spectral analysis shows the presence of ammonia hydrates, while under the influence of solar and cosmic rays, ammonia hydrates on the surface of Charon should decompose in an astronomically short time. Since 2007, based on observations from the Gemini Observatory, hypotheses about cryovolcanism on Charon have been put forward. In June 2014, a group of scientists led by Alice Roden, studying the shape of Charon's orbit, suggested that Charon once had an underground ocean.
On July 14, NASA's automatic interplanetary station New Horizons flew through the Pluto-Charon system. As part of the mission, photographs of Charon were obtained from various distances (the shortest distance during the flight was about 28,800 km).
Charon's surface: optical image (up) and height map (at the bottom). |
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NASA video of Charon's surface flyby (computer graphics based on data obtained by New Horizons) |
At the end of July 2015, mission staff published a map of Charon and Pluto. Features on Charon's surface have been informally named after proper names and authors of science fiction and fantasy: the Clark and Kubrick mountains, the craters of Kirk, Spock, Uhura and Sulu (characters from Star Trek), Darth Vader, Luke Skywalker and Princess Leia (character from Star Trek). wars"), Ripley and the Nostromo Canyon (a character and ship from "Aliens"), the Tardis Canyon and the Gallifrey region (respectively the apparatus and planet from Doctor Who), the Vulcan regions (a planet from Star Trek) and Mordor (a country from "The Lord of the Rings").
For example, Mordor is a dark spot near the north pole of Charon, formed due to ultra-low temperatures that periodically occur on the surface of the satellite. During the polar winter, which can last hundreds of years, the surface temperature drops to −258 °C, and methane and nitrogen molecules captured by Charon's gravity from Pluto's atmosphere freeze. When “summer” comes and the temperature of the North Pole rises again, reaching −213 °C, methane and nitrogen evaporate, and in the Mordor region only heavy compounds remain, which, under the influence of ultraviolet radiation, turn into tholins.
Features of Charon's surface should be named according to four themes approved by the International Astronomical Union in February 2017:
- goals and intermediate stages of fictional space and other travel;
- fictional and mythological ships in space and other travels;
- fictional and mythological sailors, travelers and pioneers;
- writers and artists associated with space exploration, in particular Pluto and the Kuiper Belt.
In popular culture
see also
Notes
- Stern, S. A., et al. The Pluto system: Initial results from its exploration by New Horizons (English) // Science: journal. - 2015. - Vol. 350, no. 6258. - P. 249-352. - DOI:10.1126/science.aad1815.
- A S T R O K U R E R
- Circular No. 3241 (undefined)