By: Trump Vang

As of today, Pluto stands as a dwarf planet that orbits farther than Neptune. Many describe it as a cold and airless world, one with a year of 248 Earth years. Pluto hasn’t always been like this though, rather filling in a role much bigger than what it is today.

On February 18th, 1930, Pluto was discovered by Clyde Tombaugh. Previously there were eight planets in the solar system, and many anticipated the surprise of a ninth planet out in the edges of the system. Their suspicions were correct, and Tombaugh’s intense searching through the night sky would find this ‘planet’.

Many had expected the planet to have a similar size to the 8th planet, Neptune, but they were to be disappointed. As more information came about Pluto, estimates on its size soon shrank. From a Neptune sized object, Pluto was downsized to an Earth sized object, then all the way down to being even smaller than Mercury.

Although Pluto’s size had been properly found, it was still considered a planet. Nothing else would change that, until the discovery of another ‘planet’ within that area.

Pluto was in a region, known as the Kuiper belt. This area of the solar system contained many small icy asteroids, orbiting all together in the shape of a belt. The Kuiper Belt also contained other spherical objects, just like Pluto. Though due to the fact that Pluto still stood as the largest out of these objects, it held onto its planetary status.

This was until the discovery of another spherical object, Eris. Pluto and Eris were very similar in size, though Pluto still reigned bigger in the size department. Though once Eris’s weight (mass) was calculated, it was found that Pluto wasn’t exactly the largest in this group of objects anymore.

For some time, many accepted Pluto, Eris, and a few others as planets, but others saw the issue with this. If they kept accepting these celestial objects as ‘planets’, they would just keep finding more, and before they knew it, they would have a multitude of planets to sort through. To combat this, scientists knew they would have to put a stop to this planet
finding.

In 2006, the IAU (International Astronomical Union) set guidelines for classifying planets. There were three rules in specific that were used to determine an object’s classification:

1. The object orbits around the Sun
2. It has enough mass to keep a spherical shape
3. The orbit that the object takes, must be cleared (So, the object orbits by itself, having enough gravitational mass to clear its orbit)

Pluto had passed the first two rules, though its classification as a planet was knocked down by the third rule. Orbiting in the Kuiper Belt, there were trillions of small objects, showing Pluto’s inability to clear its orbit. Due to this, Pluto’s status as a planet was removed.

Ever since that point, there have been just 8 planets in the solar system. Pluto and its other spherical friends were all demoted to the classification under the term, ‘Dwarf Planet’.

More dwarf planets have been discovered ever since the term’s creation. Pluto still stands as one of the largest objects within this classification.

Although not being a planet, the world is still interesting in many aspects. Recently, a spacecraft named New Horizons visited this world, showing its surface and moon system to us. Pluto is truly a fascinating world, showing what beauty can be found, even in the outer stretches of the solar system.