discovery to controversial reclassification,# Pluto is truly one of a kind so we're going## to dive into the history of that and what# makes Pluto such a unique world in our solar system.

The discovery of Pluto began in the early# 1900s when astronomer Percival Lowell first suggested## that there was another planet beyond Uranus# and Neptune that was tugging on their orbits.## Astronomers were on the hunt for this theoretical# Planet X and they found Pluto and deemed it the## ninth planet in our solar system and the rest# is history - except that part where Pluto is not## actually a planet.

As time went on, astronomers# also discovered Charon, one of Pluto's five moons.## Pluto and Charon are like the dynamic duo.

They're# known as our solar system's only double planetary## system and this is because Charon orbits Pluto in# such a way that it neither rises nor sets.

Their## surface are always facing each other, plus Charon# is about half the size of Pluto, which is pretty## large in comparison.

Our own moon is tiny in# comparison to Earth.

Imagine if it was half the size.

Pluto was considered the ninth planet# in our solar system up until 2006 when the## International Astronomical Union reclassified# the status of Pluto as a dwarf planet.

This made## news all over the world and it sparked quite# a bit of controversy in astronomy circles and## outside of them.

Scientists debated back and# forth whether or not this should still hold## true.

Some are still not completely sold on that# new definition and are debating to this day, but## ultimately, here are the three criteria the IAU# follows to classify a full-sized planet.

One,## it is in orbit around the Sun.

Pluto's got# that, done.

Two, it has enough mass to become## round in shape due to its self-gravity, which# is also true for Pluto.

But then three, it has## cleared the neighborhood of its orbit.

This is# where Pluto falls short.

Pluto's gravitational## pull is not dominant in its orbital path around# the Sun and it's actually crossing orbit with## Neptune.

Sometimes Pluto is closer to the Sun# than Neptune is.

Not to mention, Pluto isn't the## only dwarf planet.

There are four other Pluto-sized# bodies in the solar system: Ceres, Haumea, Makemake, and Eris.

If we reclassify Pluto to be, you know, a# fully-fledged planet, what would become of these## other dwarf planets?

So as much as we would love# to call Pluto our ninth planet, it's technically## not true today, but Pluto is still just as cool# and unique as it's ever been.

It has an icy## mountainous surface.

It's got five beautiful# moons.

It makes a pretty spectacular dwarf## planet I got to say.

We'll see you next time on# Star Gazers, everyone.

Remember keep looking up!## For more Star Gazers, click the video below.

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