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Why Is Pluto Not A Planet Anymore?

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Why Pluto Is Not A Planet Anymore

Why Pluto Is Not A Planet Anymore

How Many Planets In The Solar System

Growing up, I completed many school projects, and one I recall most favourable was a project on our solar system. Using styrofoam balls, sticks and coloured paints, I constructed a unique-looking solar system with all 9 planets. Why 9 planets? Well that is how many planets there were when I was growing up.

Yes, 9 planets in the solar system.

Each with their own defining features, size and distance from the sun.

You would have been correct in any trivia contest if you said the planets were Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

However, give this answer today and you would be wrong. Wrong? How can that be? Well, put simply, it is because Pluto is not considered a planet anymore.

Believe it or not!

Education for Kids

History of Pluto

Pluto was discovered in 1930 by an astronomer from the United States of America, and was identified as the smallest planet in our solar system and the 9th planet from the sun.

According to NASA, Pluto is:

  • located more than 5.8 billion kilometres from the sun.
  • Approximately 40 times as far from the sun as Earth is.
  • A huge 2.300 kilometres wide.
  • Very cold - temperature on Pluto ranges from 375 - 400 degrees below zero.

Pluto orbits the sun following an oval path, taking 248 years per cycle, and sometimes is closer to the sun than at other times. One day on Pluto is about 6.5 days on Earth.

Visiting Pluto

A mission to Pluto is underway.

NASA launched its first mission to Pluto in 2006 under the name of 'New Horizons' which is scheduled to arrive in 2015. A 9 year journey. The New Horizon's spacecraft is about the size of a piano and is expected to spend at least 5 months investigating its new surroundings.

The spacecraft is fitted with cameras to take photos of Pluto which will be sent back to the astronomers so that they can learn far more about Pluto, the dwarf planet, than ever before.

Why Pluto Is Not A Planet Anymore

On August 24th 2006, an organisation of professional astronomers passed a resolution which revoked Pluto's status as a planet.

Pluto is not considered a planet anymore

Pluto is now categorised as a dwarf planet.

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Nothing else has changed though. It still orbits the sun like before, it is still the same size as it was before, it still looks the same however because of its size and because it cannot clear other objects out of its way, it is considered dwarf and therefore is no longer one of the 9 planets in our solar system.

So now there are not 9 planets, but 8. How bizarre!


Remembering Pluto

What is a dwarf planet?

NASA state that there are many criteria that help to correctly define and explain exactly what a dwarf planet is. The International Astronomical Union (IAU) defines a dwarf planet as ‘… is a celestial body orbiting a star.. large enough to be rounded by its own gravity...and is not a satellite..."

With the newest inclusion of Pluto there are five dwarf planets: Pluto, Eris, Makemake, Haumea and Ceres.

Here's a comical view associated with Pluto no longer being a planet

Remember this for your school projects, trivia competitions or keep it under your hat and be the smart one out of your friends.

Pluto is not a planet. Pluto is a dwarf planet.

Don't forget that there are now only 8 planets in our solar system.

Time to re-write history!

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2012 WorkAtHomeMums


WorkAtHomeMums (author) from Australia on March 31, 2012:

@singular insanity - i feel the same :)

Singular Insanity on March 31, 2012:

How sad for Pluto! Don't worry though, you will always be a planet to me.... ;-)

Davesworld from Cottage Grove, MN 55016 on March 26, 2012:


I understood that Pluto's demotion was largely a result of its highly elliptical which periodically brings it inside the orbit of Neptune. This orbit makes it look more like a captured object and less like something that was created along with the other eight.

Ramkeyviswa from Chennai, India on March 26, 2012:

Dear WorkAtHomeMums,

You can also add another point in this. Once in 20 years, Neptune becomes the farthest planet from the sun and Pluto occupies its position.

WorkAtHomeMums (author) from Australia on March 25, 2012:

thanks vocalcoach - yes I read that also - couldn't quite verify so omitted it from this hub but never the less an amazing fact isn't it.

Audrey Hunt from Pahrump NV on March 25, 2012:

I read recently that the name pluto was named by an 11 year old. Just wondering if that is true?

An excellent and informative hub. Very interesting. Voted up and thank you!

WorkAtHomeMums (author) from Australia on March 25, 2012:

I wasn't suggesting they in particular re-wrote history, more that it is time to re-write history. A lot of learnings to be re-learnt so to speak. With time comes wisdom and in this case clarification and correction.

scottcgruber on March 25, 2012:

I don't think the IAU rewrote history. They just defined what a planet was. The definition we inherited from the Greeks was merely "wanderer," which really didn't help much when astronomers started discovering all these odd Pluto-sized Kuiper Belt objects in eccentric, tilted orbits. Either we define them all as planets and have a solar system of 20 and growing, or have eight Classical Planets and a bunch of other stuff.

I prefer the latter.

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