Pluto- dwarf planet solar system: discovery, name, size, mass, orbit, composition, atmosphere, satellites, what planet Pluto is, research, photo.

Pluto- the ninth or former planet of the solar system, which has passed into the category of dwarfs.

In 1930, Clyde Tomb made the discovery of Pluto, which became the ninth planet for a century. But in 2006, it was transferred to the family of dwarf planets, because many similar objects were found beyond the line of Neptune. But this does not negate its value, because now it is in second place in terms of size among the dwarf planets in our system.

In 2015, the New Horizons spacecraft reached it, and we received not only close-up photos of Pluto, but also many useful information. let's consider Interesting Facts about the planet Pluto for children and adults.

Interesting facts about the planet Pluto

Namegot in honor of the ruler of the underworld

• This is a later variation of the name Hades. She was offered by an 11-year-old girl Venice Brunei.

Became a dwarf planet in 2006

• At this point, the IAU puts forward a new definition of "planet" - a celestial object that is on an orbital path around the Sun, has the necessary mass for a spherical shape and has cleared the surroundings of foreign bodies.

• In the 76 years between detection and shift into a dwarf type, Pluto managed to pass only a third of the orbital route.

There are 5 satellites

• The lunar family includes Charon (1978), Hydra and Nikta (2005), Kerberos (2011) and Styx (2012).

largest dwarf planet

• Previously, it was believed that this title deserves Eris. But now we know that its diameter reaches 2326 km, while Pluto has 2372 km.

1/3 is water

• The composition of Pluto is represented by water ice, where there is 3 times more water than in earth's oceans. The surface is covered with ice crust. Visible ridges, light and dark areas, as well as a chain of craters.

Smaller than some satellites

• The larger moons are Gynymede, Titan, Io, Callisto, Europa, Triton and the earth satellite. Pluto reaches 66% of the lunar diameter and 18% of the mass.

Endowed with an eccentric and inclined orbit

• Pluto lives at a distance of 4.4-7.3 billion km from our Sun star, which means it sometimes comes closer to Neptune.

Received one visitor

• In 2006, the New Horizons probe set off for Pluto, arriving at the object on July 14, 2015. With its help, it was possible to obtain the first approximate images. Now the device is moving towards the Kuiper belt.

Pluto's Position Predicted Mathematically

• This happened in 1915 thanks to Percival Lowell, who based himself on the orbits of Uranus and Neptune.

Periodically an atmosphere

• As Pluto approaches the Sun, the surface ice begins to melt and forms a thin atmospheric layer. It is represented by nitrogen and methane haze with a height of 161 km. The sun's rays break the methane into hydrocarbons, covering the ice with a dark layer.

Discovery of the planet Pluto

Pluto's presence was predicted even before it was found in the survey. In the 1840s Urbain Verrier applied Newtonian mechanics to calculate the position of Neptune (then not yet found) based on the displacement of the orbital path of Uranus. In the 19th century, a close study of Neptune showed that its peace is also disturbed (transit of Pluto).

In 1906, Percival Lowell founded the search for Planet X. Unfortunately, he died in 1916 and did not wait for the discovery. And he did not even suspect that Pluto was displayed on two of his plates.

In 1929, the search resumed, and the project was entrusted to Clyde Tomb. 23 year old boy spent whole year, taking pictures of celestial areas, and then analyzing them to find the moments of displacement of objects.

In 1930, he found a possible candidate. The observatory requested additional photos and confirmed the presence of a celestial body. On March 13, 1930, a new planet in the solar system was discovered.

Name of the planet Pluto

After the announcement, the Lowell Observatory began to receive a huge number of letters suggesting names. Pluto was a Roman deity in charge of the underworld. The name comes from 11-year-old Venetia Burney, who was prompted by her astronomer grandfather. Below are photos of Pluto from the Hubble Space Telescope.

It was officially named on March 24, 1930. Among the competitors appeared Minevra and Cronus. But Pluto fit perfectly, as the first letters reflected the initials of Percival Lowell.

The name quickly became accustomed. And in 1930, Walt Disney even named the dog Mickey Mouse Pluto after the object. In 1941, the element plutonium was introduced by Glenn Seaborg.

Size, mass and orbit of the planet Pluto

With a mass of 1.305 x 10 22 kg, Pluto occupies the second position in terms of massiveness among the dwarf planets. The area indicator is 1.765 x 10 7 km, and the volume is 6.97 x 10 9 km 3.

Physical Characteristics of Pluto
Equatorial radius	1153 km
Polar radius	1153 km
Surface area	1.6697 10 7 km²
Volume	6.39 10 9 km³
Weight	(1.305 ± 0.007) 10 22 kg
Average density	2.03 ± 0.06 g/cm³
Acceleration free fall at the equator	0.658 m/s² (0.067 g)
first cosmic speed	1,229 km/s
Equatorial rotation speed	0.01310556 km/s
Rotation period	6.387230 seat days
Axis Tilt	119.591 ± 0.014°
declination of the north pole	−6.145 ± 0.014°
Albedo	0,4
Apparent magnitude	up to 13.65
Angular diameter	0.065-0.115″

Now you know what planet Pluto is, but let's study its rotation. The dwarf planet moves along a moderate eccentric orbital path, approaching the Sun by 4.4 billion km and moving away by 7.3 billion km. This suggests that it sometimes comes closer to the Sun than Neptune. But they have a stable resonance, so they avoid collision.

It takes 250 years to pass around the star, and completes the axial rotation in 6.39 days. The slope is 120°, which results in remarkable seasonal variations. During the solstice, ¼ of the surface is constantly warming up, and the rest is in darkness.

The composition and atmosphere of the planet Pluto

With a density of 1.87 g/cm3, Pluto has a rocky core and an icy mantle. The composition of the surface layer is 98% nitrogen ice with a small amount of methane and carbon monoxide. An interesting formation the Heart of Pluto (Tombo Region) stands out. Below is a diagram of the structure of Pluto.

The researchers think that inside the object is divided into layers, and the dense core is filled with rocky material and surrounded by a mantle of water ice. In diameter, the core extends for 1700 km, which covers 70% of the entire dwarf planet. The decay of radioactive elements indicates a possible subsurface ocean with a thickness of 100-180 km.

A thin atmospheric layer is represented by nitrogen, methane and carbon monoxide. But the object is so cold that the atmosphere solidifies and falls to the surface. The average temperature reaches -229°C.

Pluto's moons

The dwarf planet Pluto has 5 satellites. The largest and closest is Charon. It was found in 1978 by James Christie, who was looking at old photographs. The rest of the moons are hidden behind it: Styx, Nyx, Kerberus and Hydra.

In 2005 Hubble telescope found Nyx and Hydra, and in 2011 - Kerberos. Styx was noticed already during the flight of the New Horizons mission in 2012.

Charon, Styx and Kerberos have the necessary mass to form into spheroids. But Nyx and Hydra seem elongated. The Pluto-Charon system is interesting in that their center of mass is located outside the planet. Because of this, some are inclined to believe in a double dwarf system.

In addition, they stay in a tidal block and are always turned one side. In 2007, water crystals and ammonia hydrates were noticed on Charon. This suggests that Pluto has active cryo-geysers and an ocean. Satellites could have formed due to the impact of Plato and a large body at the very beginning of the origin of the solar system.

Pluto and Charon

Astrophysicist Valery Shematovich on Pluto's icy moon, the New Horizons mission, and the Charon ocean:

Classification of the planet Pluto

Why is Pluto not considered a planet? In orbit with Pluto in 1992, similar objects began to be noticed, which led to the idea that the dwarf belongs to the Kuiper belt. This made me think about the true nature of the object.

In 2005, scientists found a trans-Neptunian object - Eris. It turned out that it is larger than Pluto, but no one knew if it could be called a planet. However, this was the impetus for the fact that they began to doubt the planetary nature of Pluto.

In 2006, the IAU launched a dispute over the classification of Pluto. The new criteria required being in solar orbit, having enough gravity to form a sphere, and clearing the orbit of other objects.

Pluto failed on number three. At the meeting, it was decided that such planets should be called dwarfs. But not everyone supported this decision. Alan Stern and Mark By actively opposed.

In 2008, another scientific discussion was held, which did not lead to a consensus. But the IAU approved the official classification of Pluto as a dwarf planet. Now you know why Pluto is no longer a planet.

Exploration of the planet Pluto

Pluto is difficult to observe because it is tiny and so far away. In the 1980s NASA has begun planning for the Voyager 1 mission. But they still focused on Saturn's moon Titan, so they could not visit the planet. Voyager 2 also did not consider this trajectory.

But in 1977, the question of reaching Pluto and trans-Neptunian objects was raised. The Pluto-Kuiper Express program was created, which was canceled in 2000, as funding ran out. In 2003, the New Horizons project started, which set off in 2006. In the same year, the first photos of the object appeared during testing of the LORRI instrument.

The device began to approach in 2015 and sent a photo of the dwarf planet Pluto at a distance of 203,000,000 km. Pluto and Charon were displayed on them.

The closest approach happened on July 14, when we managed to get the best and most detailed shots. Now the device is moving at a speed of 14.52 km / s. With this mission, we received a huge amount of information that has yet to be digested and realized. But it is important that we also better understand the process of system formation and other such objects. Next, you can carefully study the map of Pluto and photos of the features of its surface.

Click on the image to enlarge it

Photos of the dwarf planet Pluto

The beloved baby no longer acts as a planet and has taken its place in the category of dwarfs. But high resolution photos of Pluto demonstrate interesting world. First of all, we are met by the "heart" - the plain captured by Voyager. This is a crater world, which was previously considered the most frosty, remote and small 9th ​​planet. Pictures of Pluto will also demonstrate the large satellite Charon, with which they resemble a double planet. But space it does not end there, because there are many more ice objects further on.

Pluto's "Badlands"

Pluto's Magnificent Crescent

Blue Sky Pluto

Mountain ranges, plains and foggy hazes

Smoke layers over Pluto

Ice flats in high definition

This high-resolution photo was obtained by New Horizons on December 24, 2015, showing the area of ​​Sputnik Plain. This is the part of the image where the resolution is 77-85m per pixel. You can see the cellular structure of the plains, which could lead to a convective explosion in nitrogen ice. The image contained a band 80 km wide and 700 km long, stretching from the northwestern part of the Sputnik Plain to the ice part. Performed with the LORRI instrument at a distance of 17,000 km.

Second mountain range found in Pluto's 'heart'

Floating hills in Sputnik Plain

Diversity of Pluto's landscape

New Horizons captured this high-resolution image of Pluto (July 14, 2015), which is considered the best zoom out to 270 m. The section extends 120 kilometers and is taken from a large mosaic. It can be seen how the surface of the plain is surrounded by two isolated ice mountains.

Wright Mons in color

The reaction of the New Horizons team to the latest image of Pluto

Heart of Pluto

Complex surface features of the Sputnik Plains

Huge heart-shaped region in the front center. Several craters are visible, and much of the surface looks recycled rather than ancient. Pluto. Credit: NASA.

After its discovery by Clyde Tombaugh in 1930, Pluto was considered for almost a century. In 2006, it was classified as a "dwarf planet" due to the discovery of other trans-Neptunian objects (TNOs) of comparable size. However, this does not change its significance in our system. In addition to large TNOs, it is the largest and second most massive dwarf planet in the Solar System.

As a result, much of the exploration time was devoted to this former planet. And with the successful flyby of it by the New Horizons mission in July 2016, we finally have a clear idea of ​​what Pluto looks like. As scientists became bogged down in massive amounts of data being sent back, our understanding of the world grew by leaps and bounds.

Opening:

The existence of Pluto was predicted before its discovery. In the 1840s, the French mathematician Urban do Le Verrier used Newtonian mechanics for (which had not yet been discovered), based on perturbations (perturbations of the orbit). In the 19th century, inhabitant observations of Neptune led astronomers to believe that some planet was perturbing its orbit.

In 1906, Percival Lowell, an American mathematician and astronomer who founded the Lowell Observatory in Flagstaff, Arizona in 1894, initiated a project to search for "Planet X", a possible ninth planet. Unfortunately, Lowell died in 1916 before the discovery was confirmed. But unbeknownst to him, his surveys of the sky recorded two faint images of Pluto (March 19 and April 7, 1915) that simply were not noticed.

The first photographs of Pluto, dated January 23 and 29, 1930. Credit: Archives Department of the Lowell Observatory.

After Lowell's death, the search was not resumed until 1929, at which time the director of the Lowell Vesto Observatory, Melvin Slifer, was assigned the task of finding Planet X with Clyde Tombaugh. 23-year-old astronomer from Kansas, Clyde Tombaugh, next year by photographing patches of the night sky and then analyzing the photographs to determine if any objects have moved out of place.

On February 18, 1930, Tombaugh discovered a possible moving object on photographic plates taken in January of that year. After the observatory received additional photographs to confirm the existence of the object, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930. The mysterious Planet X has finally been discovered.

Naming:

After the opening, it was announced that the Lowell Observatory was inundated with proposals for names. new planet. , named after the Roman god of the underworld, was suggested by Venetia Burney (1918-2009), then an 11-year-old schoolgirl in Oxford, England. She suggested it in a conversation with her grandfather, who suggested the name to astronomy professor Herbert Hall Turner, who informed his colleagues in the United States.

The surface of Pluto as seen by the Hubble Space Telescope in several images in 2002 and 2003. Credit: NASA/Hubble.

The object was given official name March 24, 1930, and it came to a vote between three options - Minerva, Kronos and. Every member of the Lowell Observatory voted for Pluto and it was announced on May 1, 1930. The choice was based on the fact that the first two letters in the word Pluto - P and L - correspond to the initials.

This name quickly caught on among the general public. In 1930, Walt Disney was apparently inspired by this event when he presented to the public a bloodhound for Mickey named Pluto. In 1941, Glenn T. Seaborg named the newly discovered element plutonium after Pluto. This followed the tradition of naming elements after recently discovered planets - such as uranium, named , and neptunium, named .

Size, mass and orbit:

With a mass of 1.305±0.007 x 10²² kg - which is the equivalent of and - Pluto is the second largest dwarf planet and the tenth largest famous object in direct orbit around the sun. It has a surface area of ​​1.765 x 10 7 km and a volume of 6.97 x 10 9 km.

A map of Pluto's surface with informal names for several of the larger features in the landscape. Credit: NASA/JHUAPL.

Pluto has a moderately eccentric inclined orbit that oscillates. This means that Pluto periodically gets closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding.

Pluto has an orbital period of 247.68 Earth years, meaning it takes almost 250 years to complete one complete orbit around the sun. Meanwhile, the period of rotation around its axis (one day) is equal to 6.39 Earth days. Like Uranus, Pluto rotates on its side with an axial tilt of 120° relative to the orbital plane, resulting in extreme seasonal changes. At its solstice, one quarter of the surface is in permanent daylight, while the other three quarters are in permanent darkness.

Ingredients and Atmosphere:

With an average density of 1.87 g/cm³, Pluto's composition is differentiated between an icy mantle and a rocky core. The surface consists of more than 98% nitrogen ice with impurities of methane and carbon monoxide. The surface is very variable with great differences in brightness and color. Distinctive feature is an .

theoretical internal structure Pluto, consisting of 1) frozen nitrogen, 2) water ice, 3) rock. Credit: NASA/Pat Rawlings.

Scientists also suspect that Pluto's internal structure is differentiated, with rock settled in a dense core surrounded by a mantle of water ice. It is believed that the diameter of the core is approximately 1700 km, 70% of the diameter of Pluto. Due to the decay of radioactive elements, it is possible that the thickness of 100-180 km at the boundary of the core and mantle.

Pluto has a thin atmosphere composed of nitrogen (N 2 ), methane (CH 4 ) and carbon monoxide (CO ) that are in equilibrium with their surface ices. However, the planet is so cold that during part of its orbit, the atmosphere thickens and falls to the surface. The average surface temperature of the planet is from 33 K (-240°C) at aphelion to 55 K (-218°C) at perihelion.

Satellites:

Pluto has five known moons. The largest and closest to Pluto's orbit is Charon. This satellite was first identified in 1978 by astronomer James Christie using photographic plates from the United States Naval Observatory (USNO) in Washington, DC. with a multiple orbit - Styx (Styx), Nix (Nix), Kerberos (Kerberos) and Hydra (Hydra), respectively.

Nyx and Hydra were discovered simultaneously in 2005 by the Pluto companion team using the Hubble telescope. The same team discovered Cerberus in 2011. The fifth and final moon of Styx was discovered in 2012 while photographing Pluto and Charon.

An illustration comparing the scale and brightness of Pluto's moons. Credit: NASA/ESA/M.Showalter.

Charon, Styx, and Kerberos are massive enough to collapse into a spheroid shape under their own gravity. Nyx and Hydra, however, are elongated. The Pluto-Charon system is unusual in that it is one of the few systems in , whose barycenter lies above the surface of the planet. In short, causing some scientists to claim that it is a "double dwarf system" instead of a dwarf planet and a moon in its orbit.

In addition, it is also unusual in that each body has a tidal lock (synchronous rotation) with each other. Charon and Pluto are always facing the same side to each other, and from any location on the surface of either, the other is always in the same position in the sky, or always hidden. This also means that the periods of rotation around the axis of each of them are equal to the time it takes for the whole system to turn around common center wt.

In 2007, observations by the Gemini Observatory of patches of ammonia hydrates and water crystals on Charon's surface suggested the presence of . This would seem to indicate that Pluto has a warm subsurface ocean and that the core is geologically active. Pluto's moons are believed to have been formed by a collision between Pluto and a similarly sized celestial body in ancient history solar system. The collision ejected matter, which then consolidated into satellites around Pluto.

Classification:

Since 1992, a lot has been discovered celestial bodies, orbiting in the same region as Pluto, demonstrating that Pluto is part of a population of . This put its official status as a planet in question, many asking if Pluto should be considered separate from its surrounding population, like Pallas, Juno and Juno, which lost their planet status after.

On July 29, 2005, the discovery was announced, which was believed to be much larger than Pluto. Initially referring to the tenth planet of the Solar System, there was no consensus on whether Eris is a planet. Moreover, others in the astronomical community consider its discovery a strong argument for reclassifying Pluto as a minor planet.

The discussion came to a close on August 24, 2006, with the resolution of the International Astronomical Union (IAU), which created the official definition of the term "planet". According to the XXVI IAU General Assembly, a planet must meet three criteria: it must be in orbit around the Sun, it must have sufficient gravity to compress itself into a spherical shape, and it must clear its orbit of other objects.

Pluto does not satisfy the third condition because its mass is only 0.07 of the mass of all objects in its orbit. The IAU has also ruled that bodies that do not meet the third criterion should be called dwarf planets. On September 13, 2006, the IAU included Pluto, Eris and its satellite Dysnomia in the Catalog of Minor Planets.

The decision of the IAU was met with mixed reactions, especially in the scientific community. For example, Alan Stern, principal investigator for the New Horizons mission, and Mark Buie, astronomer at the Lowell Observatory, have both been outspoken about the reclassification. Others, such as Mike Brown, the astronomer who discovered Eris, have voiced their support.

Our evolving understanding of Pluto, represented by Hubble images from 2002-2003 (left) and photographs taken by New Horizons in 2015 (right). Credit: theguardian.com

On August 14-16, 2008, researchers from both sides of the issue gathered for what came to be called "The Great Planet Debate" at Johns Hopkins University's Applied Physics Laboratory. Unfortunately, no scientific consensus was reached, but on June 11, 2008, the IAU announced in a press release that the term "plutoid" would be used to refer to Pluto and other similar objects in the future.

(OPK). This led to planning for the Pluto Kuiper Express mission, and NASA instructed the Jet Propulsion Laboratory to schedule a flyby of Pluto and the Kuiper Belt.

By 2000, the program was revised due to expressed budget problems. After pressure from the scientific community, a revised mission to Pluto, dubbed New Horizons, finally received funding from the US government in 2003. The New Horizons spacecraft successfully launched on January 19, 2006.

From September 21 to 24, 2006, the New Horizons spacecraft managed to capture its first photographs of Pluto while testing an instrument called LORRI. These images, taken from a distance of approximately 4.2 billion km or 28.07 AU, were released on November 28, 2006, confirming the spacecraft's ability to track distant targets.

Remote rendezvous operations with Pluto began on January 4, 2015. From January 25 to 31, the approaching probe took several images of Pluto, published by NASA on February 12, 2015. These photographs, taken from over 203 million km away, showed Pluto and its largest moon, Charon.

Pluto and Charon recorded by the New Horizons spacecraft from January 25 to 31, 2015. Credit: NASA.

The New Horizons spacecraft made its close approach to Pluto at 11:49:57 UTC on July 14, 2015, followed by Charon at 12:03:50 UTC. Telemetry confirming the successful flyby and the "health" of the spacecraft reached Earth at 00:52:37 UTC.

During the flyby, the probe captured the clearest images of Pluto to date, and complete analysis the data obtained will take several years. Spaceship currently moving at 14.52 km/s relative to the Sun and 13.77 km/s relative to Pluto.

While the New Horizons mission has shown us a lot about Pluto and will continue to do so as scientists analyze the collected data, we still have a lot to learn about this distant and mysterious world. Over time and large quantity missions to we can finally unravel some of its deepest secrets.

An illustration of the New Horizons spacecraft near Pluto, with Charon visible in the background. Credit: NASA/JPL.

In the meantime, we offer all the information that is currently known about Pluto. We hope you find what you're looking for in the links below and enjoy your exploration as always!

The title of the article you read "Dwarf Planet Pluto".

Yes, yes, it's true. Pluto is no longer a planet. Didn't you know? This "fresh" information appeared a little over 10 years ago. However, according to estimates "by eye", about half of the adult visitors to planetariums are surprised by this fact. But the children in this matter are at their best, they know for sure that there are eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune). But to the question "Why is Pluto no longer a planet?" may not always be answered. Why did they do this to him and who are these "scoundrels," explains astronomer, lecturer at the St. Petersburg Planetarium Maria Borukha.

So what happened to Pluto back in 2006?

Some people believe that Pluto has left the solar system. We hasten to reassure: Pluto is in place and has not left us. It still revolves around the Sun with a period of 248 Earth years and, most likely, will do so for a very, very long time.

It's all about the names that astronomers use to classify objects. It was they who decided not to call Pluto the word "planet" anymore.

Imagine that one child gave another toy. There used to be Petya the engine, and Colin the engine became. Although the toy itself has not changed at all, we began to call it differently. Something similar happened with the waters of the Indian, Pacific and Atlantic Oceans surrounding Antarctica - in 2000 they were recognized as a separate Southern Ocean.

Same with Pluto:Until 2006, Pluto was called the "planet" of the solar system, and now it is called the "dwarf planet". It is important that dwarf planets (they are marked with arrows in the figure below) are not a subclass of "planets" (they can also be easily distinguished in the image) - this new type objects in the solar system, which was introduced in that same 2006. Now it includes five objects: Ceres, Pluto, Haumea, Makemake and Eris.

How are planets and dwarf planets different?

It can be seen from the figure above that, firstly, all dwarf planets are smaller than planets. So maybe Pluto is just too small or light to be called a real planet? And this was only discovered in 2006?

No, the size of Pluto was known accurately enough until 2006 to conclude that it is not much, but smaller than Mercury (the status of the smallest planet passed to it).

Moreover, many bodies of the solar system, even bigger size than Mercury are not included in the list of planets (for example, Ganymede is the largest satellite of Jupiter). And our Moon, a well-known cosmic body from ancient times, is, of course, smaller than Mercury, but at the same time larger than Pluto!

Yes, if the Moon lived separately from the Earth and revolved around the Sun, it could receive the status of a planet. Now it is called a satellite and is unlikely to change its status in the near future.

We understand this word intuitively and say that the Moon is a satellite of the Earth, and the Earth is a satellite of the Sun, implying the movement of one body around another. But formalizing the definition of this term has proved so difficult that the International Astronomical Union has not yet introduced a precise definition of the word "satellite".

Now we can come to the conclusion: in order to be called a planet, it is important not only to be a sufficiently large body, but it is also necessary to be a satellite of the Sun, and not another body.

But Pluto fits that definition! Maybe he, being a large body, flies in some special orbit around the Sun?

Partly yes.

With this drawing, you can almost accurately represent the scale of the solar system and the position of the orbits of the planets. It is striking that the orbit of Pluto is strongly inclined - by as much as 17 degrees in relation to the plane in which the Earth's orbit lies. Next comes Mercury, whose inclination is only 7 degrees.

In addition to its anomalously high inclination, Pluto's orbit is more elongated than the orbits of the planets, although the difference from Mercury in this parameter is small.

Maybe this is the answer: Pluto's orbit is too elongated and too tilted?

Let's now look at the orbits of bodies that are farther from the Sun than Pluto (they are highlighted in red in the figure below). This can be done more clearly with the help of this resource.

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Dwarf planets of the solar system. A photo:

So what property is common to such different objects, which at the same time distinguishes them from the planets?

It turns out that it is necessary to consider not only the bodies themselves, their size and orbit, but also pay attention to what is in their vicinity: the small bodies of the solar system are mostly asteroids.

It is in this region of the solar system that main asteroid belt lives one of the dwarf planets - Ceres. By the way, the classification of this object was also changed: earlier, Ceres was considered an asteroid (it was the first discovered celestial body of its kind), and now it is one of the dwarf planets.

The difference between asteroids and dwarf planets is in their shape. Dwarf planets are massive enough to be round, while asteroids are lighter bodies and have irregular shapes.

The other four dwarf planets live much farther from the Sun, beyond the orbit of Neptune. And in the same region of the solar system is the Kuiper belt - another asteroid belt.

Now we can conclude that the dwarf planets of the solar system differ from the planets mainly in the presence of asteroids in the vicinity of their orbits.

At the same time, dwarf planets and planets have a rounded shape and revolve around the Sun.

And what was the reason to lower the status of Pluto?

Ideas that Pluto should no longer have the status of a planet began to appear at the beginning of the 21st century. After 70 years of Pluto's tenure as the ninth planet, one after another, discoveries of bodies that are further than Pluto, but comparable in size and mass, rained down. The final chord in the sequence of discoveries was the discovery of Eris in 2005 by a group of scientists led by Michael Brown. Subsequently, he even wrote the book "How I Killed Pluto."

The fact is that Eris turned out to be significantly more massive than Pluto and actually began to claim the role of the 10th planet. The scientists had a choice: to continue expanding the list of planets, or to come up with a definition for the word planet that would ensure peace and stability in their family. They chose the second path and gave the following definition to the word planet:

1. A body that revolves around the sun.
2. Massive enough to take on a near-circular shape under the influence of gravity forces, and in a state of hydrostatic equilibrium.
3. Clearing the space of its orbit from other bodies.

Does this mean that the list of planets will never be replenished again? In no case! Until now, new objects, usually small ones, are regularly discovered in the solar system. But even with the existing variety of powerful telescopes, a planet the size of the Earth, but located 500 times farther from the Sun than the Earth itself, astronomers would not be able to notice. Moreover, in January 2016, the same "Pluto killer" Michael Brown predicted the existence of a large planet (10 times more massive than the Earth!) On the visible outskirts of the solar system. During 2016, this hypothetical object (predicted theoretically, but not necessarily existing in reality) was not found. But it is possible that in the coming years, astronomers will find a real ninth planet that will be more worthy of this status than Pluto.

General information about Pluto

© Vladimir Kalanov,
website"Knowledge is power".

Shortly after the discovery of Neptune, made in September 1846 by the German astronomer Johann Galle according to the calculations of Adams and Le Verrier, the idea arose to search for a new planet beyond the orbit of Neptune. It was assumed that an unknown planet could have an influence on the features of the movement of Uranus (along with the influence of Neptune, Saturn and Jupiter).

Pluto

History of the discovery of Pluto

Back in 1848, the American mathematician and astronomer Benjamin Pierce (1809-1880) hypothesized the existence of a trans-Neptunian planet. In 1874, another American astronomer, Simon Newcomb (1835-1909), developed a new theory of the motion of Uranus that took into account the gravity of an unknown planet beyond Neptune.

An American astronomer, known for his work, Percival Lowell (1855-1916), devoted 14 years of hard work to the search for this planet. He organized a large-scale search for the ninth planet of the solar system, indicated a place in the constellation of Gemini where to look for an unknown planet, but premature death did not give him the opportunity to complete the work he had begun. 14 years after Lowell's death, on March 13, 1930, the American astronomer Clyde Tombaugh, who worked in an observatory near the city of Flagstaff (Arizona), built at the time with Lowell's money, discovered the ninth planet. It was exactly where Percival Lowell had calculated.

We consider it our duty to note that Clyde Tombaugh, who at the time of discovery was only 24 years old, came to this outstanding success as a result of huge, painstaking work, working as an operator of a blink comparator - a special device that allows you to compare two photographs of the same area sky, taken at different times with a photographic telescope, Clyde Tombaugh had to analyze and compare hundreds of photographic plates, sitting at the blink-comparator microscope.

On the photographic plates there were reflections of faint stars, the number of which, as they approached the Milky Way strip, ranged from 160 thousand to 400 thousand on each plate. What perseverance and what industriousness one had to possess in order to carefully analyze these records!

Later it turned out that Pluto could have been discovered during Lowell's lifetime, as well as in 1919. The processing of the surviving photographic plates of the Flagstaff Observatory using modern technology showed that the image of the new planet on one of the plates fell on a defect in the photographic plate, while on the other the images were so fuzzy that it was simply impossible to notice them.

In the name, more precisely in the astronomical sign of the planet Pluto, a certain symbolism is visible: two Latin letters P and L coincide with the initial letters of the name Persival Lowell. Although such a coincidence is probably accidental, it is perceived as some kind of historical justice. If we turn to mythology, then Pluto among the ancient Greeks was the god of the underworld, the abode of the dead. Not at all a fun name was given to the ninth planet, but let's not take it seriously, a myth is a myth.

Before continuing the story about Pluto, we immediately make a reservation that the term "planet" in relation to this celestial body is no longer applied. In August 2006, the XXVI Assembly of the International Astronomical Union took place in Prague, which decided that Pluto is not a full-fledged planet of the solar system and, due to its size, is transferred to the category dwarf planets . I must say that among astronomers this decision was perceived ambiguously and, on the whole, rather restrained.

General information about Pluto

Pluto is the smallest and most distant planet in the solar system.. Pluto is at an average distance of 5,900 million kilometers (39.9 AU) from the Sun. A characteristic feature of Pluto's motion is the large elongation of its circumsolar orbit and its large inclination to the plane of the ecliptic. Approaching one of its extreme positions in its orbit (toward perihelion), Pluto is for some time closer to the Sun than Neptune. Indeed: the minimum distance of Neptune from the Sun is 4456 million km, and Pluto - 4425 million km. The last such period when Neptune was the most distant planet occurred in the years from 1979 to 1998.

Schematic: Orbits of Neptune and Pluto

There is no need to be surprised at the long duration of this period (19 years), because the period of revolution of Pluto around the Sun is 248 years. But the most distant point of Pluto's orbit is 7375 million km from the Sun. At this point, Pluto is already incomparably farther from the Sun than Neptune.

It turns out that with an appropriate location in space relative to the Sun, our Earth can be at a distance from Pluto equal to approximately 7525 million km. At such a huge distance, the study of the planet Pluto is very difficult. In the most powerful telescope, Pluto and its satellite look from the Earth in the form of a small star, almost merged with another, even smaller one.

True, with the help of, launched into near-Earth orbit, scientists were able to obtain a certain amount of information about these distant celestial bodies. For example, the diameter of Pluto is determined - 2390 km, which is almost two times less than the diameter of Mercury (4878 km) and much less than the diameter of the Moon (3480 km).

The period of rotation of Pluto around its own axis is 6 days and 8 hours, i.e. A day on Pluto lasts 152 Earth hours. Pluto's rotation around its axis has a direction opposite to the direction of its rotation in its orbit. This is another feature of this planet.

The mass of Pluto is 0.0025 of the mass of the Earth (400 times less than the mass of the Earth). The inclination of the orbital plane to the plane of the ecliptic is 17 ° 2 ". None of the other eight planets of the solar system has such a large inclination of the orbital plane. For example, this parameter is: for Neptune - 1 ° 8", for Uranus - 0 ° 8 " Saturn has 2°5", Jupiter has 1°9".

The period of revolution around the Sun, i.e. a year on Pluto is, as we already know, 248 Earth years, i.e. almost a quarter of a millennium.

The average speed of revolution around the Sun is 4.7 km / s, or almost 17,000 km / h.

We can imagine a pilot at the controls of a jet aircraft flying at a speed of just over 1,000 km/h for several hours. But one cannot imagine the flight of such an aircraft along the orbit of Pluto. Such a flight is unthinkable, because it would take 4200 years to fly around the Sun in the orbit of Pluto at a speed of about 1000 km / h: after all, it would be necessary to fly about 22.2 billion km.

We give this fantastic calculation because we are talking about the most distant planet in the solar system. Space is fraught with many mysteries, and who knows if people will be able to discover another planet. Perhaps the orbits of Neptune and Pluto are the boundaries of the solar system. And so, to give readers an idea of ​​the size of the space contained within these boundaries, we have given this simple calculation.

Atmosphere and surface of Pluto

Pluto's atmosphere was discovered in 1985 by observing its occultation of stars. The presence of an atmosphere was subsequently confirmed by observations of other occultations in 1988 and 2002.

Pluto's atmosphere is very rarefied and consists mainly of a mixture of nitrogen (99%), carbon monoxide and methane (0.1%). The main component of the atmosphere is molecular nitrogen (N 2). It is assumed that nitrogen was formed from the substance that makes up the surface of Pluto. At present, nitrogen is in a volatile (sublimated) state. At an average atmospheric temperature of minus 230°C, this is the natural state of aggregation of nitrogen. According to updated data, the temperature of the atmosphere (minus 180°C) is higher than the surface temperature of the planet (minus 230°C). Sublimation has a cooling effect on the surface of Pluto.

Molecules and ions of hydrogen, hydrocyanic acid, ethane and other substances formed as a result of photochemical processes and the impact of charged particles are also present in the atmosphere. It is believed that methane existed during the formation of the planet and came out of its depths.

At an altitude of 1215 km, atmospheric pressure is about 2.3 microbars. At this altitude, the atmosphere seems to be divided into two parts. Above is a layer of aerosol from a mixture of the above substances. With distance from the Sun, the sublimation of surface ice decreases and, accordingly, the pressure decreases.

Thanks to images from the Hubble Space Telescope, scientists have an idea of ​​about 85 percent of Pluto's surface. The surface of Pluto appears in the form of contrasting zones - from light to dark. Some dark areas can be considered formations similar to craters and depressions, which appeared as a result of collisions with large asteroids.

Surface of Pluto

Pluto's surface is made up of water ice and frozen methane. The bright areas of the surface are areas presumably covered with solid nitrogen. Nitrogen status changes as long seasonal cycles change. A change in the structure of nitrogen leads to a change in the brightness of the surface. Depending on the temperature conditions, the structure of water ice also changes. When Pluto approaches the Sun, part of the ice sublimates, i.e. turns into gas, and the atmosphere becomes denser. When the planet moves away from the Sun, the atmosphere partially condenses and falls out in the form of crystals, forming a kind of "snow" on the surface. This results in lighter areas of the surface.

Three types of Pluto
Photo of the surface based on images from the Hubble telescope

Homogeneous grayish spots, which were "examined" with the help of the Hubble telescope, are formed by methane. This is confirmed by spectroscopic studies performed from the Earth. Methane makes up about 1% of the planet's mass.

One of the components of Pluto's surface may be carbon dioxide, the content of which is less than 1%. It is possible that the composition of the surface, in addition to these substances, includes other components, but so far they have not been identified.

The density of matter on Pluto averages 2.03 (g/cm³). Surface temperature - from minus 228 to minus 238 °C. Surface pressure ranges from 3 to 160 microbars. The illumination of the surface is weak: the distance from the Sun is too great. However, during the daytime, Pluto's surface is illuminated many times more than our Earth is illuminated by the Moon at night.

Much about Pluto remained unknown until 2015, when the New Horizons probe flew past it.

The heterogeneity of Pluto's surface has been confirmed by much better pictures from the New Horizons probe.

The albedo of different parts of its surface varies from 10 to 70%, which makes it the second most contrasting object in the solar system after Iapetus.

The internal structure of Pluto

Pluto is a special planet, but most likely it can be attributed to the terrestrial planets. According to the main hypothesis, it is believed that under the surface, consisting mainly of frozen water and methane, there is an icy mantle up to 250 km thick, consisting of ice (a layer of 130 km), molecular nitrogen and other structures. Deeper is a core of stony silicates and partly of ice and hydrates. According to one version, between the icy mantle and the silicate core, there may be a layer of organic matter up to 100 km thick.

Ice on the surface and in the mantle was formed from water raised from the depths of the planet by heat, which was released during the radioactive decay of elements that make up the rocky formations of the core. Other suggestions on the subject are that water was released from the planet's primordial fossils as a result of a collision with a large asteroid.

© Vladimir Kalanov,
"Knowledge is power"

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Pluto is the most distant planet. From the central luminary, it is on average 39.5 times farther than our Earth. Figuratively speaking, the planet moves on the periphery of the Sun's domain - in the arms of eternal cold and darkness. That is why it was named after the god of the underworld, Pluto.

However, is it really so dark on Pluto?

It is known that light weakens in proportion to the square of the distance from the source of radiation. Consequently, in the firmament of Pluto, the Sun should shine about one and a half thousand times weaker than on Earth. And yet it is there almost 300 times brighter than our full moon. From Pluto, the Sun is seen as a very bright star.

Using Kepler's third law, it can be calculated that Pluto makes a revolution in its circumsolar orbit in almost 250 Earth years. Its orbit differs from the orbits of other large planets by its significant elongation: the eccentricity reaches 0.25. Due to this, the distance of Pluto from the Sun varies widely and periodically the planet "enters" inside the orbit of Neptune.

A similar phenomenon occurred from January 21, 1979 to March 15, 1999: the ninth planet became closer to the Sun (and to the Earth) than the eighth - Neptune. And in 1989, Pluto reached perihelion and was at a minimum distance from the Earth, equal to 4.3 billion km.

Further, it was noticed that Pluto experiences, although insignificant, but strictly rhythmic variations in brightness. The period of these variations researchers identify with the period of rotation of the planet around its axis. In terrestrial units of time, it is 6 days 9 hours and 17 minutes. It is easy to calculate that there are 14,220 such days in a Pluto year.

Pluto is noticeably different from all planets far from the Sun. Both in size and in many other parameters, it is more like an asteroid captured into the solar system (or a system of two asteroids). Pluto is about 40 times farther from the Sun than the Earth, therefore, naturally, the flow of solar radiant energy on this planet is more than one and a half thousand times weaker than on Earth. However, this does not mean that Pluto is shrouded in eternal darkness: the Sun in its sky looks brighter than the Moon for the inhabitants of the Earth. But, of course, the temperature on the planet, to which the light from the Sun takes more than five hours, is low - its average value is about 43 K, so that only neon can remain in Pluto's atmosphere without experiencing liquefaction (lighter gases due to the low force gravity is removed from the atmosphere). Carbon dioxide, methane and ammonia solidify even at the maximum temperature for this planet. In the atmosphere of Pluto, there may be minor impurities of argon, and even smaller amounts of nitrogen. The pressure at the surface of Pluto, according to available theoretical estimates, is less than 0.1 atmospheres. Data on Pluto's magnetic field are not yet available, but according to the theory of the baroelectric effect, its magnetic moment is an order of magnitude lower than that of the Earth. The tidal interactions of Pluto and Charon should also lead to the appearance of an electric field.

In recent years, thanks to the improvement of observational methods, our knowledge of Pluto has been significantly replenished with new interesting facts. In March 1977, American astronomers detected spectral lines of methane ice in Pluto's infrared radiation. But a surface covered with hoarfrost or ice should reflect sunlight much better than one covered with rocks. After that, I had to reconsider (and for the umpteenth time!) the size of the planet.

Pluto cannot be larger than the Moon - such was the new conclusion of specialists. But how to explain then the irregularities in the motion of Uranus and Neptune? Obviously, their movement is perturbed by some other celestial body, still unknown to us, and perhaps even several such bodies ...

The date of June 22, 1978 will go down forever in the history of the study of Pluto. You can even say that on this day the planet was rediscovered. And it began with the fact that the American astronomer James Christie was lucky to discover a natural satellite near Pluto, called Charon.

From refined ground-based observations, the radius of the satellite's orbit relative to the center of mass of the Pluto-Charon system is 19,460 km (according to the Hubble orbital astronomical station - 19,405 km), or 17 radii of Pluto itself. Now it has become possible to calculate the absolute dimensions of both celestial bodies: the diameter of Pluto was 2244 km, and the diameter of Charon was 1200 km. Pluto really turned out to be smaller than our moon. The planet and the satellite rotate around their own axes synchronously with the orbital motion of Charon, as a result of which they face each other with the same hemispheres. This is the result of prolonged tidal braking.

In 1978, a sensational message appeared: in a photograph taken by D. Christie with a 155-cm telescope, the image of Pluto looked elongated, that is, it had a small protrusion. This gave grounds to assert that Pluto has a satellite located quite close to it. This conclusion was later confirmed by images from spacecraft. The satellite, called Charon (according to Greek mythology, this was the name of the carrier of souls to the kingdom of Pluto Hades across the river Styx), has a significant mass (about 1/30 of the mass of the planet), is located at a distance of only about 20,000 km from the center of Pluto and revolves around it with a period of 6.4 Earth days, equal to the period of revolution of the planet itself. Thus, Pluto and Charon rotate as a whole, and therefore they are often considered as a single binary system, which allows us to refine the values ​​of masses and densities.

So, in the solar system, Pluto turned out to be the second double planet, and more compact than the Earth-Moon double planet.

By measuring the time that Charon spends on a complete revolution around Pluto (6.387217 days), astronomers were able to "weigh" the Pluto system, that is, determine the total mass of the planet and its satellite. It turned out to be equal to 0.0023 Earth masses. Between Pluto and Charon, this mass is distributed as follows: 0.002 and 0.0003 Earth masses. The case when the mass of the satellite reaches 15% of the mass of the planet itself is unique in the solar system. Before the discovery of Charon, the largest ratio of masses (satellite to planet) was in the Earth-Moon system.

With these sizes and masses, the average density of the components of the Pluto system should be almost twice that of water. In a word, Pluto and its satellite, like many other bodies moving on the outskirts of the solar system (for example, satellites of giant planets and comet nuclei), should consist mainly of water ice mixed with rocks.

On June 9, 1988, a group of American astronomers observed Pluto's occultation of one of the stars and discovered Pluto's atmosphere in the process. It consists of two layers: a haze layer about 45 km thick and a "clean" atmosphere layer about 270 km thick. The researchers of Pluto believe that at a temperature of -230 ° C prevailing on the surface of the planet, only inert neon is still able to remain in a gaseous state. Therefore, the rarefied gaseous shell of Pluto may consist of pure neon. When the planet is at the farthest distance from the Sun, the temperature drops to -260 ° C and all gases must “freeze out” from the atmosphere completely. Pluto and its moon are the coldest bodies in the solar system.

As you can see, although Pluto is located in the region of domination of the giant planets, it has nothing in common with them. But with their "ice" satellites, he has a lot in common. So Pluto was once a moon? But what planet?

The following fact may serve as a clue to this question. For every three complete revolutions of Neptune around the Sun, there are two such revolutions of Pluto. And it is possible that in the distant past, Neptune, in addition to Triton, had another large satellite that managed to gain freedom.

But what force was able to throw Pluto out of the Neptune system? "Order" in the Neptune system could be disturbed by a massive celestial body flying by. However, events could also develop according to another "scenario" - without the involvement of a perturbing body. Celestial mechanical calculations showed that the approach of Pluto (then still a satellite of Neptune) with Triton could change its orbit so much that it moved away from Neptune's sphere of gravity and turned into an independent satellite of the Sun, that is, into an independent planet ...

In August 2006, at the General Assembly of the International Astronomical Union, a decision was made to exclude Pluto from the major planets of the solar system.