The Pluto is the largest Kuiper belt object in the solar system. The Pluto is the dwarf planet which covered with ice and situated in Kuiper belt and ninth largest object in solar system orbiting the Sun. The Pluto was believed as ninth planet of solar system which was discovered by Clyde Tombaugh in 1930. Discovery of many other objects of similar sized in Kuiper belt, Pluto was announced as Dwarf planet in 2006.
Properties of Pluto
- The Pluto was discovered on 18 February 1930 by Clyde W.Tombaugh.
- It was named after Roman God of underworld which was proposed by eleven years old girl Venetia Burney.
- The Pluto has rocky core and icy mantle.
- It has no magnetic field and no rings.
- The diameter of Pluto is 2376.6 km and mass is 1.303 X 1022 km.
- The Pluto has rocky core and water ice mantle.
- One year on Pluto is equal about 248 earth’s years and one day is about 6.348 earth’s days.
- Maximum distance from the Sun is 7.37 billion km and minimum distance is 4.43 billion km.
- Orbital path of Pluto is about 17o inclined to the elliptical plane.
- Axial tilt of Pluto is 120o and surface temperature is -240o C.
- Main component of atmosphere of Pluto is Nitrogen and small amount of Methane and Carbon Monoxide also.
- Climate of Pluto is divided into five zones which are Tropic, Arctic, Tropical Arctic, Diurnal and Polar.
- Pluto has five moons which are Charon, Styx, Nix, Kerberos and Hydra.
- Orbital speed of the Pluto is 4.743 km/s.
The formation of the Pluto is the puzzle for astronomers. As per one theory, the Pluto is the moon of Neptune which was knocked out by Triton, the largest moon of Neptune. But Study shows that Pluto never approaches to orbit of Neptune. The Pluto is a residual planetesimal around the sun which failed fully to convert into a fully fledged planet.
The internal structure of the Pluto consists of inner Core and surrounded by Mantle. The core is made of rocky material. The diameter of core is 1700 km which is about 70% of diameter of Pluto. The sub surface of water ocean of about 100km to 180 km is surrounded the core which separate the core and mantle. The core is covered by mantle which is made of water ice. The Pluto has no Magnetic field.
The outer surface is made of about 98% of Nitrogen ice and some amount of Methane and Carbon Monoxide. The Pluto’s surface has vast difference in brightness and colour. The nitrogen and carbon monoxide is rich at 180o latitude while methane is rich at 300o latitude. Colour of the Pluto is from more orange to less reddish. The “Heart” a large bright area opposite side of Charon, its moon is 1000 km wide basin of Nitrogen and Carbon monoxide ice. The surface of the Pluto contains mountains, valleys, craters and plains. The mountains are 2 to 3 km in height and big ice blocks. Most of the plains are covered by frozen nitrogen gas so not visible any crater.
Orbit and Rotation
The orbit of the Pluto is chaotic and most eccentric than other planet in solar system. Its orbital period is 248 years. Its orbital path is 17o inclined to the elliptical plane. The orbital speed of Pluto is 4.743 km/s. The closest distance from the Sun (Perihelion) is 4.43 billion km while farthest distance from the Sun (Aphelion) is 7.37 billion km.
The rotation period of Pluto on its axis is 6.387 days. As like the Uranus, Pluto also rotates by sides with axial tilt of 120o which creates tremendous seasonal variation. The temperature on surface is -240oC.
The atmosphere of the Pluto is composed mainly Nitrogen and some amount of Methane and Carbon Monoxide which are in form of ice on its surface. Due to high energy cosmic radiation, gases create more complex molecules like ethane, ethylene, acetylene, hydrocarbons, hydrogen cyanide. The Pluto is covered by multi layers haze which is about 20 layers. The density of atmosphere of Pluto is very low.
The Pluto has no any troposphere but about 4km thick tropospheric layer with temperature about -236oC. Above this layer, stratosphere is present in which temperature is increased as height due to green house effect of methane. Maximum -173o C temperature is obtained at the height of 20 to 40 km and after that it decreases and about 200km temperature reaches to -193o C and after that it remains constant. The Pluto’s atmosphere losses about 1 X1023 Molecules of Nitrogen and 5X1025 molecules of Methane per second. As molecules escape to outer atmosphere they are ionized by solar radiation.
According to sub-solar latitude, the climate of Pluto is divided into five layers which are Tropics, Arctic, Tropical arctic, Diurnal and Polar. Some of the zones have fix boundary while some has variable boundary because obliquity range from 103o to 127o over 2.8 million years oscillation period.
Most of the Pluto’s surface lies in Tropics region. The Permanent Tropics zone gets direct sun light from the Sun. At the current obliquity of 120o, Tropics range from latitude 60o N to 60oS. When the obliquity reaches to minimum at 103,o tropics range from latitude 77o N to 77o S which covers about 97 % off Pluto’s surface. When obliquity reaches to maximum 127o, tropics range from 53oN to 53oS which covers about 80% of Pluto’s surface.
In arctic climate zone during one orbit, the Pluto faces continues darkness during winter and continues sunlight during summer. The Permanent Arctic Zone covers the planet from latitude from 90o N to 37oN in northern hemisphere while 90 o S to 37o S in southern hemisphere which covers about 40% area of Pluto. Due to axial tilt of Pluto, arctic zones vary during its oscillation cycle. During current 120o tilting position, arctic zones cover the surface of Pluto from 30o N to 90 o N and 30o S to 90o S which is about 50% of surface area. When tilting will be 103o, it covers from 13o N to 13 o S which is about 78% of total area.
The tropical arctic zone is the overlapping area of both Tropic and Arctic zone which is possible when tilting of Pluto is between 45o to 135o. The tropical arctic zone covers the region between latitude 13o N to 77o N in northern hemisphere and 13o S to 77o S in southern hemisphere which cover 75% of total surface area. As like Tropic and Arctic zone, Tropical Arctic zone also vary in area covered due to oscillation of planet but latitude between 37o to 53o in both the hemisphere remain stable during whole oscillation cycle. So, this band is called Permanent Tropical Arctic Zone which belongs to 20% of area. Maximum tropical arctic zone lies between 13o to 77o latitude in both hemispheres which is about 75 % of area. During current 120o tilting, this zone lies from 30o N to 30o S latitude which covers about 20% of area.
The Permanent Diurnal zone lies between 13o N to 13o S in both hemisphere at equal from both side of equator which covers 22% of total area of Pluto. The narrowest band of diurnal zone is occurred when tilting is to minimum to 103 o, occurred about 0.8 million years ago. This portion is facing continues Sunrise and Sunset during every 6.4 days for 10 million years. During current tilting of 120o, Diurnal zone lies between 30o N to 30o S covers 50 % of total surface area.
The Polar zone is the area at which sun light never reach on its any orbital cycle during whole obliquity cycle. The Permanent Polar zone lies between 77o to 90o latitude in each hemisphere which covers about 3% of total surface area of planet. Maximum area of polar zone is covered under 53o to 90o latitude in both hemispheres. At 120o present tilting, polar zone lies between 60o to 90o latitude in both hemispheres which over 13% area of Pluto.
Moons of Pluto
The moons of the Pluto have been formed by collision of Pluto and same sized body. The Pluto has five natural satellite or moons. According to the distance from the Pluto, they are Charon ( largest moon of Pluto), Styx, Nix, Kerberos and Hydra.
The Charon was discovered by James Christy on 22 June 1978. It was the half the diameter of the Pluto which is tidally locked. Remaining four moons are small circumbinary moons. The moons orbits are circular and coplanar with equator of Pluto.
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Authored by BK Suthar.
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