Why is Pluto NOT a Planet? An Open Blog Post

My Very Eager Mother Just Served Us Nine Pizzas. 

I think we'll have to change it to My Very Eager Mother Just Served Us Nachos. No more Pizza! It's a shame because I was kind of in the mood for pizza!

If you're a little lost right now it might be because your 3rd grade teacher didn't tell you about the same mnemonic that mine did. The first letter of each of the 9 words (now 8) represents a planet: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and (Pluto).

So why no Pluto? Sure he's really small and really cold, but that's no reason to hate a guy!  It's a little more than the physical aspects of Pluto that no longer classify it as a planet.

The International Astronomical Union (IAU) voted on a new definition of the word "planet" some time ago. The new definition: A full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit.

Well, most scientists agree that pluto doesn't exactly dominate the neighborhood around its orbit. Therefore, it is no longer considered a planet. 



What DOES dominate the neighborhood then?

Although Pluto is the largest object in the immediate neighborhood, its moon Charon is about half the size. Other planets are much larger than their surrounding moons. So Pluto  is (in a sense) being kicked out for being too small. Well, at least relative in size to Charon.

What does this all mean?

This means textbooks must be changed, maps of our solar system too. It also means Pluto will have to be on the outside looking in for a very long time. I was surprised when I heard the news. I mean, we were always taught that there were nine planets in the solar system. You don't expect that one day someone will change the definition on you and BAM! you have one less planet. It doesn't truly have an impact on anything (other than Pluto's feelings). Pluto is still there, doing what it has been doing for millions of years. That won't change. The only thing that changes is our definition of a planet.

National Geographic - Pluto Not a Planet, Astronomers Rule

Works Cited

Inman, Mason. "Pluto Not a Planet, Astronomers Rule." National Geographic.            National Geographic Society, 24     Aug. 2006. Web. 13 Sept. 2012.