For around 75 years, the dwarf planet Pluto was considered the 9th planet of the solar system. We have known about Pluto since 1930, but only in 2006, the celestial object was demoted to a dwarf planet after the discovery of Eris, another dwarf planet.
Some still consider Pluto a full-fledged planet even to this day. It is one third made out of water, has no magnetic field, and it is the second-closest dwarf planet to the Sun, after Eris and the first discovered Kuiper Belt object. With that being said, here are some awesome facts about Pluto.
9 facts about the Dwarf Planet Pluto:
1. Fascinating discovery – Planet X
By using Newtonian mechanics, in 1840, the French astronomer Urbain Le Verrier discovered perturbations in the orbit of Uranus. After the discovery of Neptune, some speculated that a larger celestial object, in between these two planets, caused the disruptions.
Thus, the hypothesis of Planet X was born. Much later, in 1894, a businessman and astronomer named Percival Lowell founded the Lowell Observatory and commenced the search for Planet X in 1906.
Though Lowell passed away ten years later, his surveys captured two faint images of Pluto, but they weren’t recognized for what they were. His widow resumed the search for Planet X, and in 1929 this task was given to Clyde Tombaugh, a 23-year-old.
He discovered Planet X one year later, in 1930, however, the task of naming the newfound planet was conducted through a survey. Venetia Burney, a schoolgirl in Oxford, called the discovered object Pluto and her proposal, received the most votes. She received a modern equivalent of 450 USD as a prize. The final choice of the name was helped in part by the fact that the first letters of Pluto are the initials of Percival Lowell.
2. Classification Controversy
A matter which holds controversy to this day is Pluto’s demotion as a planet to a dwarf planet. Some NASA officials in high positions opt for Pluto’s reclassification as a planet, and at the same time, others consider it a planet regardless of the International Astronomical Union’s (IAU’s) classification.
This is further backed up by the fact that NASA’s New Horizons spacecraft revealed a greater complexity of Pluto while observing the planet in 2015, such as an underground ocean, organic materials on the surface, and a multilayered atmosphere.
Pluto was classified as a planet for 75 years, but it was demoted to the status of a dwarf planet when similar objects were discovered in the Kuiper Belt.
The requirements were stated by the IAU by which a celestial object can be classified as a planet:
- It has to orbit around the Sun.
- It has to be massive enough to be rounded by its own gravity
- It must have cleared the neighborhood around its orbit, which means it must be the dominant gravitational body in its orbit and consumes smaller objects.
Pluto didn’t meet the third condition, but the debate is still ongoing.
3. The surface area of Pluto is a bit bigger than Russia
In comparison with the United States, Pluto is only about half the width, with a surface area of 17.8 million km2/ 439.7 million acres. The dwarf planet’s diameter has been estimated at 2,376 km / 1,476 mi, while its radius is 1,188 km / 738 mi.
Pluto is 1/6 the size of Earth or 18%, and it has 70% the diameter of our Moon.
4. Pluto comes closer to the Sun than Neptune
Pluto is at an average distance of 39.5 AU from the Sun. At its furthest point, it reaches a distance of 48.9 AU while at its closest 29.7 AU. Its orbit is unusual, both elliptical and tilted.
The dwarf planet’s oval-shaped orbit periodically takes it closer to the Sun than Neptune. Even though they may appear to be on a collision course, their orbits are aligned in such a way that they may never approach each other tightly [1].
Another peculiarity of Pluto is that it’s spinning from East to West – retrograde motion – similarly to Uranus and Venus. Pluto completes one trip around the Sun in about 248 years, and the sunlight reaches the dwarf planet in about 5.5 hours when it is at its average distance of 39.5 AU.
Since one Plutonian year is 248 Earth years, we haven’t witnessed Pluto complete a full orbit around the Sun since its discovery.
5. The atmosphere of Pluto is similar to that of a comet
Pluto has a thin and tenuous atmosphere that expands when it comes closer to the Sun and collapses as it moves further away, such are the consequences of its unusual orbit.
At its closest point to the Sun, the ices on its surface sublimate, changing from solid to gas, and rises temporarily to form a thin atmosphere. These atmospheric gases have been traced up to 1,670 km / 1,037 mi from the surface, and it doesn’t have a sharp upper boundary [2].
Pluto’s tenuous atmosphere consists of nitrogen, methane, and carbon monoxide. NASA’s New Horizons spacecraft measured Pluto’s surface pressure and found it to be at 1 Pa, or roughly one million to 100,000 times less than Earth’s atmospheric pressure.
6. The man who discovered Pluto reached the dwarf planet!
Clyde Tombaugh discovered Pluto in 1930. He died in 1997, but his ashes were placed inside an aluminum capsule within the New Horizons spacecraft in 2006.
This is the longest known post-mortem flight in history. Clyde’s remains reached the dwarf planet in 2015.
7. Pluto has many names
The dwarf planet is named after the Roman god of the underworld, the equivalent of the Greek god Hades. Almost all languages use various transliterations for Pluto. In Japan, Pluto is known as Meiosei – Star of the King (God) of the Underworld. In Hindi, it is known as Yama, the God of Death, both in Hindu and Buddhist mythology.
Following the tradition of naming a newly discovered element after a planet, Glenn T. Seaborg named plutonium after Pluto, uranium after Uranus, and neptunium after Neptune, in 1941.
8. Pluto has five moons
In order of discovery, they are Charon – discovered in 1978, Hydra and Nix – both discovered in 2005, Kerberos – 2011, and Styx – 2012.
Charon is the largest moon. It has a mean radius of 606 km / 377 mi, being around half the diameter of Pluto, and overall the largest known moon of any dwarf planet.
Some consider Pluto/Charon as a double planet rather than a planet and a moon. The two celestial objects are tidally locked, always showing only once face towards one another, and the distance between them is about the same as from one side of South America to the far side of North America.
9.Pluto is one of the most contrastive bodies in the Solar System
Its surface is quite varied, with significant differences in both brightness and color. Saturn’s moon Iapetus is very similar to Pluto in this sense. Pluto’s colors vary from charcoal black, dark orange, white, and portions of red.
Some of the notable geographical regions are Tombaugh Regio, or the “Heart,” which is a large bright area on the side opposite Pluto’s moon Charon. Cthulhu Macula, or the “Whale,” is a large dark area on the trailing hemisphere, and “Brass Knuckles,” a series of dark equatorial regions on the leading hemisphere.
