[Thread about Pluto being reclassified as a dwarf planet]

Yeah, that Pluto that we used to know as the 9th planet of the Solar System but suddenly reconsidered as a dwarf planet. Now who thought that this was a good idea?

Hi I'm Ruru! I'm a second year Astro major. All info will be based from sources that I will provide below. I'll provide screenshots as support to my statements. I'll try to make this thread well-informed and easy to understand. If there are any errors, I'm open for corrections.

Before I get to the point, it's best to have some history lessons and background check about the subject at hand.

On February 18, 1930, Pluto was discovered by Clyde Tombaugh in the Lowell Observatory in Arizona, USA using a telescope and photographic plates. Before its discovery, Percival Lowell theorized the existence of a "trans-Neptunian" planet, that soon later confirmed it was Pluto.

But when Lowell died in 1916, the project was postponed. The project was continued in 1929 by Clyde Tombaugh, the most famous amateur astronomer. And in February 18 1930, Pluto was discovered. The discovery was publicly announced in March 13, 1930.

: If Lowell first studied the existence of Pluto, shouldn't he be the one deemed as the discoverer?

Lowell only theorized its existence based from the calculations made. But he died, so Tombaugh was assigned to work to confirm his theory and he did. So the credits goes to him.

: So where does the name "Pluto" came from?

Good question! The origin is actually cute. The name Pluto was from a Roman god of the underworld. It was suggested by Venetia Burney, an 11 year old schoolgirl in Oxford who has interest in classical mythology.

Now the history lesson is done, let's get to the real thing. What makes a planet, well, a planet?

In August 24, 2006, the IAU had a general assembly with profound astronomers from around the world. One of their resolutions was to have a clear definition of a planet.

And so they gave 3 criterias:
1. It should orbit around the Sun
2. It basically means a planet should be nearly round due to gravitational equilibrium
3. It should have a clear neighborhood on its orbit (meaning a planet has the orbit for its own)

Now beyond the planet Neptune, they found 1000 more objects. This concerned them cuz one of these object might be bigger than Pluto and they did see that there were bigger than Pluto. They started to question what makes a planet a planet. And so this was raised in the IAU meeting

Now after the decision that was made by the IAU in 2006 and began to deem the Solar System to have 8 planets instead of 9, it wasn't easily accepted the and there are still debates about it up until now.

So why Pluto was excluded?

Remember the 3rd criteria? It was discovered that the oblong orbit of Pluto was overlapping in Neptune's orbit. And since the criteria said one planet's orbit should be clear, Pluto was disqualified. And that's why Pluto became a dwarf planet.

Feel a little pissed after knowing the reason is simple and short? That this thread would be shorter if I went direct to the point? Well, I would be too, but let me tell you this.

If I suddenly give you the answer with no context, will you get it immediately? No. It's out of context and will just raise more questions. It's better to know the context and background of a subject to fully understand it.

If I didn't give the background of Pluto being one of trans-Neptunian objects which is the reason why IAU decided to make a clear definition of a planet, you'll get lost in the subject and get confused.

Now I like to explain things clearly and can make my listeners understand me and keep up with me. And in this way, we both get in the same picture with little problem as possible. Anyways, the point is, you won't get what I mean when you don't know the context of the subject.

Got any more questions about Pluto? Or do you have an astro topic you want me to discuss? Drop it in my CC!! https://curiouscat.qa/jiaqikixu 

Sources: Wikipedia and official sites of IAU, NASA, Lowell Observatory, and History Channel