Astronomy
Pluto
Dwarf planet
Is Pluto a planet?
Who Discovered Pluto?
How far is Pluto from the sun?
Is Pluto's orbit circular or eccentric?
Does Pluto have a moon?
Pluto, the largest, most distant member of the solar system, was previously thought to be the outermost and smallest planet. It was also considered to be the most recently discovered planet, discovered in 1930. In August 2006, the International Astronomical Union (IAU), which has been accused by the scientific community of classifying astronomical objects, voted to remove Pluto from the list of planets. This is a new classification of dwarf planets. This change reflects astronomers' realization that Pluto is a major member of the Kuiper Belt, a collection of ice and rock debris left over from the formation of the solar system and is now orbiting the sun outside Neptune's orbit. ۔ (For further discussion of the IAU difference between a planet and a dwarf planet and the change in Pluto's classification, see Planet.)
Pluto
Pluto as observed by the New Horizons spacecraft, July 13, 2015.
NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Pluto cannot be seen in the night sky without the aid of the eye. Its largest moon, Charon, is so close in size to Pluto that it has become common for two bodies to be called double systems. Pluto is designated by the symbol.
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Pluto is named in Roman mythology for the god of the underworld (the Greek equivalent of heads). It is so far away that sunlight, which travels at about 300,000 kilometers (186,000 miles) per second, takes more than five hours to reach it. An observer standing on the surface of Pluto will see the sun as a very bright star in the dark sky, giving Pluto an average of 1 / 1,600 of the sunlight reaching the earth. Pluto's surface temperature is so cold that ordinary gases such as nitrogen and carbon monoxide are present there as ice.
Due to Pluto's remoteness and small size, even the best binoculars on Earth and in Earth's orbit can handle very little detail of its surface. In fact, for decades, it has been difficult to determine basic information such as its radius and mass. Pluto was not visited in July 2015 by the New Horizons, a US spacecraft that flew via Pluto and its four satellites, which answered many important questions about it and its environment.
Basic astronomical data
Pluto's average distance from the Sun, about 5.9 billion kilometers (3.7 billion miles or 39.5 astronomical units), gives it a larger orbit than the outermost planet, Neptune. (An astronomical unit [AU] is the average distance of the Sun from the Earth; about 150 million kilometers [93 million miles].) Its orbit, in comparison to the planets, is unusual in many ways. It is longer than any of the orbits of the planets, or eccentric, and more inclined towards the lunar eclipse (at 17.1)), the plane of the Earth's orbit, near which the orbits of most of the planets are located. Traveling on its eccentric path around the Sun, Pluto differs from 29.7 AU, at its closest perihelion, to 49.5 AU, at its farthest aphelion. Because Neptune rotates in an almost circular path at 30.1 AU, Pluto is for a small fraction of each revolution that is actually closer to the Sun than Neptune. However, the two bodies will never collide, as Pluto is locked in a 3: 2 stabilization echo with Neptune. That is, it completes two revolutions around the sun at exactly the same time that Neptune takes to complete three. This interaction of gravity affects their orbit in such a way that they can never pass close to 17 AU. Pluto last reached Perry Helen in 1989. For about 10 years before and after that time, Neptune was farther from the sun than Pluto.
Earth observations have shown that Pluto's luminosity varies with the duration of 6.3873 Earth days, which is now well established as the period of its rotation (cidral day). Of the planets, only Mercury, which has a rotation period of about 59 days, and Venus, with 243 days, rotate more slowly. Pluto's axis of rotation is at an angle of 120 ول to the length of its orbit, so that its north pole actually points 30 ° down from the plane. (According to the convention, the top of the plane is taken in the direction of the Earth and the North Pole of the Sun; below, in the opposite direction. Tilted.) This way Pluto rotates almost in a reverse direction (opposite the direction of rotation of the sun and most of the planets); On its surface an observer would see the sun rising in the west and setting in the east.
Compared to the planets, Pluto is also unique in its physical properties. Pluto's radius is less than half that of Mercury. It is only two-thirds the size of the Earth's moon. Next to the outer planets - Jupiter, Saturn, Uranus and Neptune - it is surprisingly small. When these properties are combined with what is known about its density and structure, Pluto seems to have more in common with the large icy moons of outer planets than with any other planet itself. Its nearest twin is Neptune's moon Triton, which represents the same origin for both bodies (see Origin of Pluto and its moon below). For additional orbital and physical data about Pluto, see Table.
Basic data for Pluto
* Pluto needs time to return to the same position in the sky as the sun, as seen from Earth.
** The smallness of deviation from the cedral day is due to the very large orbit of Pluto.
Average distance from the sun 5,910,000,000 km (39.5 AU)
The eccentricity of the orbit is 0.251
The inclination of the orbit towards the lunar eclipse is 17.1
Plutonian Year (Revolutionary Period) 247.69 Earth years
Visual Intensity on Average Opposition 15.1
Mean synodic period * 366.74 Earth days
The average orbital speed is 4.72 km / s
Radius 1,185 km
Mass 1.2 x 1022 kg
The average density is about 2 g / cm
The average surface gravity is 58 centimeters per second
Escape speed 1.1 km per second
Circulation duration (Plutonin ciderl day) 6.3873 Earth days (retreat)
Plutonin ie solar day ** 6.3874 Earth days
Tilt of the equator towards the orbit (slant) 120
The average surface temperature is about 40 K (8387 ° F, −233 ° C).
Surface pressure (near paraffin) about 10−5 bar
Number of known moons 5
Pluto and Charon
A mix of fine color images of Pluto (right) and Charon (left) taken by the New Horizons spacecraft.
NASA / JHUAPL / SwRI
Pluto's atmosphere
Although the discovery of methane ice on the surface of Pluto in the 1970s (see surface and interior below) convinced scientists that the body has an atmosphere, it will have to wait until the next decade for direct observation. Its atmosphere was discovered in 1988 when Pluto passed in front of a star as observed from Earth. Before Pluto's disappearance, the star's light gradually dimmed, indicating the presence of a thin, very diffused atmosphere. Since Pluto's atmosphere must contain vapor in balance with its ice, small changes in temperature must have a large effect on the amount of gas in the atmosphere. During the years around Pluto's Peri Helen in 1989, when Pluto was a little colder than average, most of its frozen gases evaporated. At that time the atmosphere was at or near its densest, which made it a good time to study the body. In the year 2000, astronomers estimated the surface pressure in the range of a few to tens of microbars (one microbar is one millionth of the surface pressure of the earth). In aphelion, when Pluto is receiving minimal sunlight, its atmosphere cannot be identified at all.
A layer of fog over Pluto
A layer of fog over Pluto, as observed by New Horizons.
NASA / JHUAPL / SwRI
Observations made during the magic show that nitrogen was the basic gas in the plutonium atmosphere, which also contained small amounts of methane, carbon monoxide and hydrogen cyanide. (Nitrogen is an important component of Triton and Saturn's largest satellite, Titan, as well as the Earth's atmosphere.) During their flight, New Horizons determined the surface pressure to be 10 microbars, including acetylene, ethylene and ethane. Found Space. The temperature near the surface is 45 K (−228 ° C, or 7379 ° F). Fog layers can be seen up to 200 km (120 miles) high. The upper atmosphere is quite expansive, moving 1,800 kilometers (1,100 miles) above the surface, and is quite cold, which prevents nitrogen from entering space.
New Horizons near Pluto
Artist offering New Horizons spacecraft approaching Pluto and its three moons.
NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Surface and interior
New Horizons observed only one hemisphere of Pluto. This hemisphere is dominated by the Tombaugh Regio, a white heart-shaped field. The western half of the Tombaugh Regio is Sputnik Planitia, a flat area of nitrogen ice that has no effect. The lack of craters suggests that Sputnik Planetia is a very young feature and thus Pluto may have some geological activity. The Tombaugh Regio is surrounded by low-lying areas with some mountain ranges. These mountains are made of water ice, which is probably floating in the surrounding nitrogen ice. The upper northern latitudes are covered by deep plains. Tombaugh is the darkest region of Pluto, west of the Regio. Originally nicknamed the "Whale" because of its shape and later called the Chattulho Reggio, the region has a diverse topography with plains, spots, mountains and strongholds. The darker color of this region is formed by organic compounds called tholan.
Mountains on Pluto
A close-up view of the mountains and plains on Pluto via the New Horizons spacecraft.
NASA / JHUAPL / SwRI
Pluto's average reflection, or albedo, is 0.72 (that is, it returns 55% of the light that falls on it), compared to 0.1 for the moon and 0.8 for Triton. However, it covers a wide range of average albedo reflections, ranging from 0.1 to 0.2 for the Chattulho Regio and 0.8 to 1 for the Tombao Regio.
The first crude infrared spectroscopic measurements (see Spectroscopy), performed in 1976, revealed the presence of solid methane on the surface of Pluto. Using new ground equipment available in the early 1990's, observers discovered ice of water, carbon monoxide, and molecular nitrogen. Although the spectral signature of nitrogen is very weak internally, it is now clear that this substance must be part of the dominant surface. Methane is present in pure methane ice patches and in nitrogen ice as a frozen "solution" of methane.
Sputnik Planetia on Pluto
High resolution image of Pluto taken by New Horizons spacecraft, combined with blue, red and infrared images taken by Ralph / Multispectral Visual Imaging Camera. The bright spread is the western lobe of the "heart" called Sputnik Planetia, which has been found to be rich in nitrogen, carbon monoxide and methane ice.
NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Pluto has a density of 1.85 grams per cubic centimeter, and Charon has a density of 1.7 grams per cubic centimeter. These values indicate that both bodies contain a significant portion of the material, such as silicate rock and organic compounds, denser than water ice (at 1 gram per cubic centimeter). The low density of charon may be due to its being more insecure or being a smaller part of the rock. Like the icy moons of Pluto, Jupiter and Saturn, there is probably an inner rocky mass surrounded by a thick sheet of water ice. The frozen nitrogen, carbon monoxide and methane visible on its surface are in the form of a relatively thin layer, similar to the water layer on the surface of the earth. Sputnik Planitia is a deep basin that may have formed as a result of an impact. It is located on the ocean axis of Pluto. That is, it is in the opposite direction of the four dwarf planets. The location of Sputnik Planitia requires extra mass beneath it, and this extra mass can be from the ocean floor above the rock cover and below the mantle of water ice.
Pluto sunset scene
Pluto's New Horizons image shows icy mountains, flat plains, and layers of fog in the air.
NASA / JHUAPL / SwRI
Pluto's moon
Pluto has five well-known moons. Charon, the largest ever, is about half the size of Pluto. It revolves around Pluto - more precisely, the two objects revolve around a common center - at a distance of about 19,640 kilometers (12,200 miles), approximately equal to eight Pluto diameters. (In contrast, the Earth's moon is slightly more than a quarter of the size of the Earth and later about 30 times the diameter of the Earth.) In other words, Charon is in orbit around Pluto. As a result, Charon is visible from only one hemisphere of Pluto. It stays in the same position on the surface of Pluto, never rises or sets (as communications satellites do in geostationary orbit above the earth; see space flight: Earth's orbit). Also, like most moons in the solar system, Charon is in a state of harmonious rotation. That is, it always presents the same face to Pluto.
Pluto Four
Pluto and its largest moon, Charon (left), as seen by the New Horizons spacecraft. They revolve around their center of gravity, and the four always face the same hemisphere as Pluto. Charon also always represents the same hemisphere because it is in a state of synchronous rotation. That is, it rotates on its axis at the same time as it orbits Pluto.
NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Charon is slightly less reflective than Pluto (less albedo - about 0.25) and more neutral in color. Its spectrum reflects the presence of water ice, which is the dominant component of the surface. There is no indication of solid methane that is so obvious to its larger neighbor. There are also ammonia spots in some of its influential pits on the surface of Charon. As discussed above on the surface and in the interior, the density of four means that the moon contains substances such as silicates and organic compounds that are denser than water ice. For additional data about Charon, see Table.
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Pluto's moon
The name means distance from the center of Pluto (radius 3 km) orbital distance (cedril period; day of the earth) Tilt of the orbit Towards the equator of the planet (degree) Eccentricity of the orbit
Four 17,536 6.387 0 0.0022
Styx 42,000 20.2
Nix 48,708 24.86 0.195 0.003
Kerberos 59,000 32.1
Hydra 64,749 38.2 0.212 0.0051
Name Rotation Length (Earth Day) * Radius or Radial Dimension (km) Mass (1020 kg) Average Density (g / cm3)
* Synchronization = synchronous rotation; Rotation and orbital periods are the same.
Charon Sync. 604 15 1.63
Styx 10-25
Knox 44 0.0058
Kerberos 13–34
Hydra 36 0.0032
Four
Charon, Pluto's largest moon, in a photo taken by the New Horizons spacecraft on July 11, 2015. This picture shows the ditch, impact craters and deep North Pole.
NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Pluto's other four moons - Hydra, Nix, Kerberos and Styx - are much smaller than the four. All four are tall. They revolve around Pluto in almost circular orbits outside of Charon's path (such as Charon) and in the same orbital plane as Charon. Hydra's orbital radius is approximately 64,721 kilometers (40,216 miles). Kerberos has 57,750 kilometers (35,884 miles); Knicks has 48,690 kilometers (30,254 miles); And Styx has 42,413 kilometers (26,354 miles). Styx, Nix, and Kerberos are reflective like Charon, while Hydra is more reflective.
For each orbit completed by Charon, Hydra completes about one-sixth of the orbit, Kerberos about one-fifth, Nix about one-fourth, and Styx about one-third. This means that the orbital periods of Hydra, Kerberos, Nix, and Styx are in the ratio 6: 5: 4: 3. These relations of orbital periods, which are in proportion to almost small whole numbers, suggest that Hydra, Nix, Kerbrus, and Styx are all four and in stable dynamic resonance with each other. That is, the five bodies pass through each other from time to time, communicating through gravity in a way that maintains the regularity of their competition. Due to the ever-changing gravitational field of Pluto and Charon (which revolve around each other), the Knicks and Hydra sometimes rotate their poles in rotation. Unlike other satellites in the solar system, Pluto's four small moons are not in rotation with the planet. That is, the duration of their rotation is not equal to their orbital period. The rotation period ranges from 0.4295 days for Hydra to 5.31 days for Kerberos.
Pluto Charon Knox; Hydra
Pluto and its three moons; Charon, Nix and Hydra - as observed by the Hubble Space Telescope.
HST Pluto Companion Search / ESA / NASA
Discovery of Pluto and its moon
When Pluto was discovered, it was thought to be the third planet discovered after Uranus and Neptune, in contrast to the six planets that have been visible in the sky with the naked eye since ancient times. The existence of the ninth planet was assumed based on the apparent turbulence of Uranus' orbital motion in the late 19th century, which suggested that a distant body was disturbing it by gravity. Astronomers later found the disturbances to be ridiculous - the small-scale gravitational pull of Pluto was not strong enough to cause a suspected disturbance. Thus the discovery of Pluto was an extraordinary coincidence that was attributed to careful observations rather than accurate predictions of the existence of a fictitious planet.
The search for the anticipated planet was most actively supported in the early 20th century at the Lowell Observatory in Flagstaff, Arizona, USA. It was started by the founder of the observatory, Percival Lowell, an American astronomer who gained notoriety for his famous claims of canal view on Mars. After two failed attempts to find the planet before Lewell's death in 1916, an astronomical camera specially designed for this purpose, capable of collecting light from a vast expanse of sky, was put into service in 1929. Was introduced, and a young amateur astronomer, Clyde Tombo, was placed to search. On February 18, 1930, less than a year after his work began, Tombao found Pluto in the Gemini Bridge. The object appeared as a faint "star" of the 15th magnitude, which gradually changed its position against the fixed background stars, following its 248-year orbit around the Sun. Although Lowell and other astronomers predicted that the unknown planet would be much larger and brighter than the object found in Tombaugh, Pluto was soon accepted as the expected ninth planet. The symbol he invented for this is ♇, for the first two letters of Pluto and for both the beginnings of Percival Lowell.
Charon was discovered in 1978 on photographs of Pluto, less than 6 kilometers (3.7 miles) from the site of Pluto's discovery, recorded by the Flag Staff at the US Naval Observatory Station. These images were recorded by James W. Christie and Robert S. Herrington in an attempt to obtain a more accurate measurement of Pluto's orbit. The new satellite is named after the boatman in Greek mythology who takes dead souls to the realm of Hades in the underworld.
One of Pluto's four moon discoveries, taken in 1978 at the US Naval Observatory Station in Flagstaff, Arizona. Charon appears only as a bulge in the upper right of Pluto's slate.
Official photo of the US Navy
Prior to Charon's discovery, Pluto was thought to be larger and larger than reality. There was no way to determine the quantity directly. Even in the discovered images, Charon appears as an unresolved collision on the edge of Pluto, due to the relative proximity of the two bodies, their extreme distance from Earth, and the distorting effects of the Earth's atmosphere. Indicates observation difficulties that arise. Only near the end of the 20th century, with the availability of the Hubble Space Telescope (HST) and ground-based instruments to compensate for the environmental turbulence, equipped with optical optics, astronomers first discovered Pluto and four. Solved in separate bodies.
Pluto Four
Pluto (center) and quadrupeds (bottom left), as observed by the European Space Agency's Fant object camera mounted on the Hubble Space Telescope.
From the National Aeronautics and Space Administration / European Space Agency
A team of neo-astronomers working in the United States discovered two small moons, Hydra and Nix, in short images taken with the Hubble Space Telescope in 2005, which traveled a short distance of 25 km (16 miles) around Pluto. Searching for items to do. To confirm the orbits, astronomers examined Hubble images of Pluto and Charon made in 2002 to study surface mapping, and two faint but definite objects moving along orbital paths calculated from 2005 images. Get hints
In 2011, six astronomers discovered the small moon Kerberos in images taken with HST. As with the discovery of Nix and Hydra, astronomers examined early Hubble images and found faint traces of Kerberos in images from 2006 and 2010. HST was re-used in 2012 to search for Styx.
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