Pluto is the largest known dwarf planet in our solar system. It was once the ninth planet but was reclassified as a dwarf planet in 2006. Pluto is named after the Roman god of the underworld.
Interesting Pluto Facts
- Until 2006 Pluto was considered as a planet in the solar system.
- It was considered the ninth and the farthest planet from the sun before it was declared as a dwarf planet. Now Neptune is the farthest planet from the sun.
- On average Pluto is approximately 5.98 billion kilometers or 40 astronomical units away from the sun.
- Pluto is named after the Roman God of the dead or of the underworld.
- Pluto takes nearly 248 years to orbit around the sun once.
- Pluto takes 6.39 Earth days to rotate about its axis once.
- Pluto is known to have 5 moons.
- Pluto rotates on its side, similar to Uranus.
- Pluto’s orbit is extremely elliptical. So much so, that sometimes it is closer to the Sun than Neptune.
- Pluto’s moon Charon is almost half of its size.
- Pluto contains more than 3 times the amount of water present in all of Earth’s oceans. However, this water is in the solid-state.
- Pluto has only been visited by one spacecraft which is New Horizons by NASA.
- Pluto is considered a dwarf planet because it does not fulfill one of the three criteria by the IAU necessary to be called a planet.
- There are five recognized dwarf planets in the solar system.
- Pluto has a heart-shaped patch on its surface.
Pluto, a Dwarf Planet
Pluto was considered the ninth and the farthest planet from the Sun until August 2006 when it was officially declared as a dwarf planet. This caused a lot of debate among scientists.
As defined by the International Aeronautical Union (IAU), a dwarf planet is any celestial body that directly orbits the sun and has enough mass to be controlled by gravitational forces. Thus, the three conditions for a body to be called a planet are to orbit around the sun, to have enough mass, and to ‘clear the neighborhood’ around its planet.
Pluto only meets the first two criteria as it has not cleared its neighborhood i.e. to become gravitationally dominant in the billions of years that it has existed, and hence, it was declared as a dwarf planet. Since 2008, NASA has acknowledged five dwarf planets in the solar system.
They are Ceres, Pluto, Eris, Makemake, and Haumea. Ceres is the only dwarf planet in the asteroid belt. It was considered a planet for many years until it was officially accepted as a dwarf planet. Pluto lies beyond Neptune. Haumea and Makemake were both discovered in 2008. Eris is sometimes called the tenth planet of the solar system.
In the 1840s, Urbain Le Verrier used calculations to predict the position and other data about Pluto which was still undiscovered. To do this, he used the data that he had about Uranus and Neptune.
In 1906, Percival Lowell proposed the existence of another planet beyond Neptune, a planet which he then called Planet X, which had an influence on the orbits of Uranus and Neptune. On 18th February 1930, Pluto was officially discovered by Clyde W. Tombaugh. The discovery was announced a few days later on 13th March 1930.
Pluto is named after the Roman god of the underworld. The name Pluto was suggested by an 11-year-old British girl named Venetia Burney. The first two letters from the name Pluto that is PL are also the reasons of Percival Lowell and hence to honor the scientist.
It was later found out that Pluto didn’t have the mass that was necessary to interfere with the orbits of Uranus and Neptune. It was different than the mass that Lowell had assumed.
The correct mass of the planet was provided by NASA’s Voyager 2. Some scholars claim that ancient Indian astronomers knew about Pluto as early as 3100 BC and that it had been mentioned in the epic poem “The Mahabharata”.
It took a long time for astronomers to find out the appearance of Pluto because of its great distance from the Earth. Pluto appears to be a brownish-yellow in color. However, the accurate color of Pluto was provided by NASA’s New Horizons.
Pluto is actually slightly orange or reddish-brown in color but less orange than Mars. On Mars, the reddish color is caused by the presence of iron oxide on the surface. The cause of this color on Pluto is however very different.
It has Brown color because of hydrocarbon molecules formed by the interaction of cosmic rays and UV light with methane. Scientists believe that the color of Pluto has become deeper with the passage of time.
Pluto seems very icy and rocky in nature. Two-third of the dwarf planet is covered with ice. Pluto is known to have 5 moons namely, Charon, Nix, Hydra, Kerberos, and Styx.
Charon, Pluto’s largest moon has roughly half the diameter of the dwarf planet and is so close to it that until New Horizon was launched, it was difficult to distinguish between the two. Charon has a silverish grey appearance. Sometimes, the two – Pluto and Charon are called a double planet system because of obvious reasons.
Pluto is about 5.98 billion kilometers or 40 AU away from the sun. The average radius of Pluto is 1,180 km. It is nearly 33% smaller than the Earth’s moon. It was the farthest and the smallest planet in the solar system until it was declared as a dwarf planet.
Pluto has a surface area of nearly 1.779×107 km2, which is nearly equal to the surface area of Russia. The period of rotation of the dwarf planet is 6.39 days on the Earth. The dwarf planet spins from east to west i.e. backward.
Most of the surface of Pluto is covered by methane and nitrogen ice. Pluto has several surface features. It has mountains as tall as 3500 meters or 11,000 feet. The average temperature on the surface of Pluto is roughly 375 °F (minus 225 °C), making it one of the coldest places in the solar system.
Scientists believe that a subsurface ocean exists or may have existed on Pluto. However, investigation about this matter is still going on. According to some scientists, Pluto could sustain life if it had oceans and enough energy.
The dwarf planet is said to have a rocky core. It also has a mantle that is composed of solid water and a core that is covered by a mixture of ices of methane, carbon monoxide and nitrogen.
Orbit & Rotation
The orbit of Pluto is highly elliptical and varies considerably. For around 20 years, Pluto is actually closer to the sun than Neptune.
Scientists are unsure about the existence of a magnetic field on Pluto. However, if it exists, it would be very weak or close to zero. This is because of the small size and slow rotation of the dwarf planet.
Pluto’s atmosphere has been of great speculations to scientists for a long time. Pluto has a very weak and thin atmosphere. It is mainly composed of methane, carbon monoxide, and nitrogen.
The density of the dwarf planet’s atmosphere increases as it goes away from the Sun. However, the atmosphere remains gaseous throughout the dwarf planet’s orbit. The atmospheric pressure on Pluto varies, it is about a hundred thousand to 1 million times less than that of the Earth.
Pluto’s atmosphere can be divided into 20 haze layers which are regularly spaced up to as high as 150 kilometers from the surface of the planet. This may be a result of pressure waves caused by Pluto’s mountains and the airflow across them.
Pluto’s atmosphere is similar to that of Triton, Neptune’s moon. Pluto is said to be a part of the Kuiper belt which consists of the remaining material after the formation of the solar system. Pluto is smaller in size than Triton but has a thicker atmosphere.
Most of the information known about Pluto and its atmosphere comes from NASA’s New Horizons spacecraft in 2015. Pluto is the only known object in the solar system beyond Neptune to have an atmosphere. Astronomers think that its atmosphere gets thicker seasonally.
Pluto is known to have 5 moons. It is believed that Pluto’s entire moon system was formed as a result of it colliding with another object of the Kuiper Belt. The moons of Pluto are named Charon, Nix, Hydra, Kerberos, and Styx.
The biggest moon of Pluto is Charon. Charon is roughly half the size of Pluto. It takes around 6 Earth days for Charon to revolve around the dwarf planet. Charon and Pluto together are sometimes called a double planet system.
They are also the biggest planet-moon system in the entire solar system. It was discovered in 1978 it is silverish grey in color. It is about 980 km above the surface of the dwarf planet and is tidally locked with it.
Nix and Hydra are small moons that were found using the Hubble Space Telescope in 2005. Kerberos is a very small moon. It is located between Nix and Hydra. It was discovered in 2011. The latest moon of Pluto to be discovered so far is Styx.
It was discovered in 2012. All the moons of Pluto have a circular orbit. All the moons of Pluto are named after figures from Roman mythology which are related to the underworld. They were suggested by an 11 year old girl named Venetia Burney.
No human being has ever visited Pluto. The first spacecraft to visit Pluto was New Horizons by the National Aeronautics and Space Administration i.e. NASA. Till today it is the only spacecraft to have flown by Pluto.
It was launched on 19th January 2006. It provided significant details about the dwarf planet, its physical characteristics, atmosphere, and moon system. New Horizons arrived at its destination in July 2015. It sent its first picture of Pluto in late September of 2006 as a part of a test.
It took 3462 days to reach Pluto from the Earth. Until 2015, the only sources of information about the dwarf planet were telescopes used for observations from the Earth. They were however not that helpful as Pluto is very far away from the Earth. No future missions of sending spacecraft’s, flybys or probes to Pluto have been proposed or approved as of today.
Potential for Life in Pluto
No evidence of life has ever been found on Pluto. It is not likely that Pluto would sustain life. Many facts and reasons support this statement.
Firstly, Pluto revolves around the sun at a distance that is very far away from it i.e. 4.98 billion kilometers or 40 astronomical units. Hence, the distance makes Pluto have a very low surface temperature of about -240 °C or -400 °F on an average.
Also, as Pluto has a very thin atmosphere that mostly consists of nitrogen, it is difficult for life to exist. The surface temperature of Pluto is also very low, about 1,00,000 times lower than that of the Earth. However, due to the presence of excess ice under the surface of the dwarf planet, some scientists do believe that Pluto has the potential to harbor life. But even if life did exist on this dwarf planet, it would be very different from that on Earth.
Pluto in Pop Culture
In Roman mythology, Pluto is the name of the god of the underworld or of death. Despite its great distance from the Earth, Pluto has been featured in a lot of materials of pop culture.
Because of it’s large from distance from the sun and the Earth Pluto has given rise to curiosity in many people, especially artists and writers. When it was declared as a dwarf planet in 2006 Pluto had received a lot of publicity.
Pluto has received mentions in Doctor Who, The Magic School Bus, Futurama, Rick and Morty, Girl Meets World, Sailor Moon, The Adventures of Pluto Nash, The Whisperer in Darkness, etc. The most popular mention of Pluto was by Disney as it is the name of Mickey mouse’s pet dog.
- 1930: Pluto is discovered
- 1978: Pluto’s moon, Charon, is discovered
- 2005: Pluto’s moons, Nix and Hydra, are discovered
- 2006: New Horizon’s spacecraft is launched
- 2006: Pluto is declared a dwarf planet
- 2015: NASA’s New Horizons spacecraft flies by Pluto