Is Pluto a Planet?

Textbooks had to be rewritten. The public was outraged. Our understanding of the solar system was forever changed on August 24, 2006, when researchers at the International Astronomical Union (IAU) voted to reclassify Pluto, changing its status from a planet to a dwarf planet. This relegation was primarily seen as a demotion and continues to reverberate. 

There was widespread public outrage when IAU demoted tiny Pluto from its position as the ninth planet of the solar system to one of five dwarf planets. When the announcement was made (and even over 16 years later), people worldwide objected to the planet’s demotion on principle, saying that it altered tradition and history rather than engaging with scientific reasoning. So, what was the IAU’s reason for demoting Pluto when it did? Why is Pluto no longer a planet anymore?

What is Pluto?

At the edge of our solar system, there’s a tiny, icy world- Pluto, a dwarf planet. A dwarf planet travels around on orbits around the sun just like other planets. 

Clyde Tombaugh- an astronomer from the United States, discovered Planet in 1930 and Venetia Burney- an 11-year-old girl from England named Pluto that same year. It is not very big in size and is only half as wide as the United States. If you lived on Pluto, you would have to wait 248 Earth years to celebrate your first birthday. One day on Pluto is about six and a half days on Earth.

Pluto has a massive glacier on its surface, but this is not a regular glacier. It is made of exotic ice. So, it’s not water ice, like we have here on Earth, but ice made out of nitrogen and methane, things that are gases in our atmosphere.

Why is Pluto not a planet?

According to the rules adopted by Astronomical Union, a celestial body must meet the following criteria in order to qualify as a planet:

1- It must be big enough to have gravity to force itself into a spherical shape.

2-  It must move in an elliptical orbit around the sun.

3- It must have a cleared neighbourhood, i.e. its gravity cleared away any debris near its orbit around the Sun.

In this case, Pluto follows the first two criteria but doesn’t follow the third criterion. It has no clear space in its orbit. Pluto still has many asteroids and debris along its orbit, rather than having absorbed them over time, as the larger planets have done.

What does it mean by “cleared neighborhood”? As planets form, they become the most dominant gravitational body in their orbit. As they interact with other smaller objects, they either consume them or suspend them away with their gravity. Pluto is not gravitationally dominant, thus not able to clear the debris in its orbit.

What are Dwarf Planets?

Dwarf planets are celestial bodies resembling planets. They do not meet all three categories of a planet, as mentioned by International Astronomical Unit (IAU). They are round in shape and orbit the sun but are unable to clear their orbital path. There are five dwarf planets recognized in our solar system, listed here in order of closest proximity to the Earth:

• Ceres: It is located in the Asteroid Belt between Mars and Jupiter, discovered in 1801
• Pluto: It is located in the Kuiper Belt, discovered in 1930
• Eris: It is located in the Kuiper Belt, discovered in 2003
• Makemake: It is located in the Kuiper Belt, discovered in 2005
• Haumea: It is located in the Kuiper Belt, discovered in 2003

Facts About Pluto

• We could never live on Pluto. Because it’s so far away from the Sun, its temperature is approximately 400° degrees below zero Fahrenheit! 
• Your weight on Pluto would be only 6% of your weight on Earth. If you weigh 50 pounds on Earth, you would weigh only approximately 3.5 pounds on Pluto.
• If you lived on Pluto, you’d have to live 248 Earth years to celebrate your next birthday. A day in pluto equals 153 hours or about 6 Earth days.
• Pluto has very hazy blue skies due to a thin atmosphere of nitrogen, methane, and carbon monoxide. 
• The largest of Pluto’s five Moons- Charon, is so big that Pluto and Charon orbit each other like double planets.

Frequently Asked Questions

1) How many moons does Pluto have?

Answer: Planet Pluto has 5 moons. The largest moon Charon, is so big that Pluto and Charon orbit each other like a double planet.

2) What is the temperature in Pluto?

Answer:  The average temperature on Pluto ranges from -387° to -369° Fahrenheit.