Facts About Dwarf Planet Pluto - The Largest Dwarf Planet

Pluto - Facts About Pluto

Pluto is the largest and second most massive dwarf planet in the solar system. Sitting far away from the rest of the planets, Plutonian world is located in Kuiper belt, a region that is beyond the orbit of Neptune. It is about 5.9 billion kilometres or 3.7 billion miles away from the sun, with an orbit that takes 248 years to complete. Similar to other Kuiper belt object, it is mainly composed of rock and ice. In fact, it is about one third water ice and two-thirds rock.

Facts About Pluto

Planet Profile

Name Pluto
Known Satellite 5
Distance from Sun (avg) 5.9 billion km
Radius 1,188.3 km
Volume 7.057 × 109 km3
Mass 1.309 × 1022 kg
Surface area 17.8 million km2
Gravity 0.62 m/s2
Max Temperature - 369 °F (- 223°C)
Min Temperature - 287 °F (- 233°C)
Length of day 6.4 Earth Days
Length of year 248 Earth years
Astronomical symbol

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Quick Facts About Pluto

  1. After its demotion to a dwarf planet, its new name is "134340 Pluto".
  2. The distance between Pluto and the Sun varies in the range from 4.4 billion kilometres to 7.3 billion kilometres.
  3. Sunlight takes 5.5 hours to reach Pluto from the Sun and 4.6 hours from the Earth.
  4. The amount of the sunlight that reaches its surface is so little that even on its brightest day, the sky would be in the twilight.
  5. Initially astronomers calculated its mass roughly to be the mass of Earth.
  6. Since its discovery, it has not completed a single orbit. It will complete the first one in the year 2178.
  7. Planet X was the name that was given to Pluto when it was discovered.
  8. Till date, only one spacecraft visited Pluto. The New Horizon spacecraft launched in 2006 and reached Pluto on 2015.
  9. The spacecraft also carried some of the ashes of Pluto's discoverer in a capsule.
  10. The transmission speed of the New Horizon probe is 1 to 4 kilobits per second.
  11. Pluto - Micky Mouse's dog, was named after the dwarf planet.
  12. Pluto has a Heart-shaped area on its surface which is named as Tombaugh Regio in the honour of its discoverer.
  13. Pluto's gravity is approximately 1/12th of ours. If you weigh 100 kg (220 LB) on Earth, you would only weigh 8kg (17 LB) on Pluto.
  14. Astronomers estimated its core to be 70% of its diameter.
  15. The mantle of Pluto is made up of Frozen water.

Detailed Facts About Pluto

  • A 23-year-old astronomer discovered Pluto in 1930

Clyde W. Tombaugh - discoverer of Pluto
Clyde W. Tombaugh

On February 18th 1930, 23-year-old Clyde William Tombaugh, an astronomer at the Lowell Observatory in Flagstaff Arizona discovered what would become a ninth planet in our solar system. Though the planet was small, the discovery was huge, leaving a massive blip on Tombaugh's occupational radar.

An impressive feat considering Tombaugh hadn't initially sought out employment at the observatory. His place behind the telescope came shortly after sending observations of Jupiter and Mars by utilising a makeshift telescope. The telescope made from a reflector and the crankshaft of a 1910 Buick and parts from a cream separator. Impressed with his innovation, the observatory enlisted Tombaugh to operate a new photographic telescope to search for what was then called Planet X.
  • The search for Pluto as Planet X was intially started in 1905

Percival Lowell
Percival Lowell

Though Clyde may have been credited with discovering Pluto, the search may not have occurred had Percival Lowell not been around. Percival had died before Pluto's discovery, but he had conducted several searches that helped narrow down its location. After the discovery of Neptune, astronomers still believed a ninth planet existed based on irregularities found within the orbit of Uranus.

Lowell began his search in 1905 and went through three unsuccessful searches. His determination was rising when rival William H Pickering made allegations of an orbit and position of a hypothetical planet. Lowell's research was continued postmortem. His family was donating time and money to the effort until its discovery in 1930.
  • An eleven-year-old girl named Pluto

The process to find pluto was a long and drawn-out. One taking years of research and much workforce, the naming of the dwarf planet was something far less complicated and involved a young, intelligent mind and a proper connections. Falconer Madden, a retired librarian from Oxford, was with his 11-year old granddaughter Venetia Burney reading out loud the discovery of a new planet then named Planet X.

When Madden was acquisitive over what the planet should be called, Benicia chimed him with Pluto after the Roman god of the underworld. Sticking with the current theme of the eight current planets, Madan composed a letter to a friend, an Oxford astronomer Herbert Hall Turner. Pluto was put up against other popular choices such as Kronos, Zeus, Atlas and Persephone. But in May of 1930, a vote among astronomers at Lowell Observatory saw Bernie's suggestion winning. Even her opinion beats out Minerva which was looking like the popular choice.
  • Pluto lost its planetary designation in 2006

Some major dwarf planet of the solar system compared to Earth
Some major dwarf planet of the solar system compared to Earth
© Wikimedia

Since its discovery, Pluto was regarded as the ninth planet in the solar system for more than 75 years. But later astronomers began to find more objects similar to Pluto. In 2005, astronomers discovered a new object beyond it that was more massive than Pluto. Initially, they mistook it for the tenth planet and named it as Eris. However, there were those that question whether the designation was ever correct.

In August of 2006 International Astronomical Union or the IAU agreed that an object should meet the following criteria to be a "Planet":

1. The object must is in orbit around the sun.
2. It has sufficient mass for its own gravity to pull it into a nearly round shape.
3. It has cleared the neighbourhood around its orbit.

Now, Pluto is in a orbit around the sun and is spherical. But since Pluto's neighbourhood has many other objects and it has not cleared its orbits. Thus it is not called a planet anymore.

At the same meeting, a new classification was formalised called a "Dwarf planet". A dwarf planet is one that meets the same first two criteria for a planet, but it has not cleared the neighbourhood around its orbit. Plus a fourth criteria the dwarf planet is not a satellite of any other object. So, Eris along with Pluto and other similar bodies that met those four criteria were downgraded to dwarf planets.
  • Pluto sometimes become the eighth planet of our solar system

Orbits of the planets of the solar system including Pluto
Orbits of the planets of the solar system including Pluto

While Pluto is known for being the farthest planet from the Sun, actually there is a moment in time when Neptune swaps its place with Pluto. Pluto's inclined elliptical and eccentric orbit around the Sun causes it to cross paths with Neptune's orbit. From the period of 1979 to 1999, Neptune was farther from the Sun than Pluto. It is a rare phenomenon that occurs for 20 years in 248-year cycles.

In 1999, Pluto slipped beyond Neptune to become the ninth. Despite this, however, there is no chance of them colliding. This is because Pluto's 248-year orbit around the Sun takes it 17 degrees above and below the plane in which Neptune and the other planets travel. Neptune and Pluto are in a so-called gravitational resonance where each planet speeds up or slows down as the other approaches. This resonance alters their paths and prevents them from coming closer than around 2.6 billion kilometres to each other.
  • Pluto rotates in a retrograde motion

Images of Pluto from different angles
Images of Pluto from different angles

We are so used to the sun's setting in the West and rising in the East. That is experiencing the same daily event on Pluto may throw us for a loop. As Pluto spins in a retrograde motion that is from east to west rather than west to east as we are used to. The rising and setting of the Sun occur in the opposite pattern. Not only this, the axis of Pluto is highly tilted. It has an axial tilt of 122° which means it is rotating on its sideways, similar to Uranus that is lying on its side.

The rotation of the planet is also considerably slower than that of Earth's. One full rotation of Pluto takes approximately 6.39 days on earth. One speculated reason for this slower rotation is the possible lack of a magnetic field.
  • The dwarf planet has five natural satellite

Charon and small moons of Pluto
Charon and small moons of Pluto

Where Earth only gets to enjoy the sight of one glowing moon, the dwarf planet Pluto has five different moons. In order of discovery the satellites are Charon - discovered in 1978, Nix and Hydra picked up by the Hubble Space Telescope in 2005, Kerberos found between the orbits of Nix and Hydra in 2011 and Styx which was discovered in 2012 when scientists were ensuring there would be no hazards for the 2015 New Horizons spacecraft.

It is believed that at one point in time, Pluto has collided with an another Kuiper Belt Object in space. The massive collision caused the material to disperse that later coalesced and created the five satellite moons. All of the Pluto's moons got its name from mythological figures associated with the underworld.
  • Pluto's relationship with its largest moon Charon is unique

Pluto's largest moon - Charon
Pluto's largest moon - Charon

Distant that around 19,570 kilometres or 12,160 miles apart, actually Pluto and Charon have a reasonably strong relationship to one another. The two are in a gravitational lock of mutual tidal locking. So regardless of the time of the day, the same face of Pluto is facing Charon and vice-versa. In relation to moons with their host planets, Charon is the largest, coming in at half the size of Pluto. An impressive girth considering our natural satellite is only 27% the size of the earth.

Pluto and Charon are considered as a part of a binary system, also known as a double planet system. Binary planet system means that any pair of planets that have almost similar mass and orbiting a common centre of gravity. The International Astronomical Union has stated that considering Charon a dwarf planet is not an impossibility in the future.
  • Pluto has a weak and unstable atmosphere

Pluto's blue skies image taken by New Horizons
Pluto's blue skies image taken by New Horizons

If you think you have it awful when your winter temperature doesn't creep above freezing. Imagine living on a planet with an average temperature that hovers around 230 degrees Celsius below zero or - 382 degrees Fahrenheit. For most of its seasons, Pluto is coated in a layer of ice. Though the sunlight reaches its surface with the same intensity, the moonlight reaches to our surface. If you clap your hands on Pluto, they will shatter like ice cubes.

Pluto has a flimsy, gaseous atmosphere that is mainly composed of nitrogen gas along with methane and carbon monoxide. Due to its inclined and elliptical orbit, the atmosphere completely freezes out and fall like snow when Pluto moves away from the sun. When Pluto moves toward the sun, the frozen atmosphere sublimates directly to gas. Due to its lower gravity, the atmosphere rises to a higher altitude than our atmosphere.
  • Pluto is a hundred times smaller than our earth

Pluto compared to Earth and the Moon
Pluto compared to Earth and the Moon

With a radius of about 1,190 km or 1,915 miles, Pluto is the largest dwarf planet. However, it is smaller than many moons of our solar system. In comparison, it is around 70% of our moon's diameter and roughly 18% of Earth's. In fact, it has less than 0.2 lunar mass. This little mass makes it the second most massive dwarf planet in the solar system. The most massive title goes to the second-largest dwarf planet Eris.

The volume of this little world is 6.39 x 109 km3. For comparison, it is 170 times smaller than the earth. In simple word, 170 Pluto could fit inside the Earth. Its density is less than 2 grams per cubic centimetre, which means that Pluto is probably made of just mostly rock and ice. There are also glaciers of solid nitrogen and water.

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