Why is Pluto not a planet

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Like why is it not included in solar system i don’t get it

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26 Answers

Anonymous 0 Comments

So, in the 19th century, we discovered a new planet between Mars and Jupiter called Ceres.

However, over time, we started discovering a ton of other, similar objects, around the same orbit. We discovered so many that we realized it didn’t make any sense to call them all planets so we classified them differently. They’re asteroids and comprise the asteroid belt.

Pluto is essentially the same story. We discovered more and more objects out there and that Pluto is just one of very, very many objects in what is now called the Kuiper belt. It makes more sense to consider Pluto a dwarf planet among many objects in the Kuiper belt rather than a planet akin to the others.

Anonymous 0 Comments

The basic answer is that since we’ve discovered Pluto, we have also discovered hundreds of other tiny planets in our solar system that are around the same size as Pluto.

If we keep Pluto as a planet, we then have to add hundreds more planets to our official list. Many scientists feel that’s just not a good idea, and felt that we should instead move Pluto to a different category along with the rest of those tiny planets we found.

Anonymous 0 Comments

The short answer is that it does not in any way dominate the region of space that represents it’s orbit around the sun. It’s not the biggest thing in it’s orbital path. It crosses Neptune’s orbit during it’s journey around the sun.

We have also discovered many other bodies like Pluto. If we call Pluto a planet, we have to call all those things planets, too.

Anonymous 0 Comments

In 2005 astronomers discovered another one, an object now called Eris.

And then another.

And another.

And another.

It quickly became apparent that there’s a vast sphere of these glorified comets out there in all sorts of wacky orbits. Pluto isn’t even the biggest one.

So this raised a conundrum – do we add dozens of new planets every few years when another wayward ice ball crosses a telescope, or does Pluto get demoted?

Eventually we decided to redefine “planet” to exclude Pluto because it obviously hasn’t cleared all the junk out of its orbit.

Anonymous 0 Comments

It is part of the solar system. But there is more in the solar system than just planets. There are also thousands of large asteroids, hundreds of thousands of comets.

And in the case of Pluto, several relatively small icy bodies, far out in the solar system. We decided that those things should not be called planets, but instead made the new designation “dwarf planet” for anything that fit that description closely, including Pluto.

Anonymous 0 Comments

Part of the current definition of a planet is that it has to clear its orbit of similar bodies. Pluto hasn’t done that, as there are many other Kuiper Belt objects orbiting in that same region. Pluto also crosses Neptune’s orbit. For a small portion of its orbit, Pluto is closer to the Sun than Neptune (this last happened from 1979 to 1999). However, Pluto’s orbit is tilted enough from the other planets that there’s no risk of collision with Neptune.

Anonymous 0 Comments

Because Pluto is smaller than Earth’s Moon.
It is a Kuiper belt object now. Along with quite a few other bodies. Likely, there will be more as time passes and we see more. Now, oddly enough, Ganymede and Titan are much bigger than earths moon and even bigger than Mercury, but they are not classified as planets because they orbit other planets.

It’s confusing up there!

Anonymous 0 Comments

A lot of comments on “we discovered other stuff” but not much on why we de-planeted Pluto vs. making the other’s planets.

We updated the definition of a planet with our increased knowledge of space. Key for this are the following

1) Planets are big enough to clear their orbits of other space-stuff. In other words, they have enough gravity to pull the stuff in their orbit into themselves, absorbing them, or their gravity “throws stuff away” out into space. Pluto has enough ‘space junk’ in it’s orbit, it’s clearly not doing this.

2) Planets have strong enough gravity to pull their shape into something close to a sphere. Smaller objects don’t have enough gravity and they have ugly shapes, like potatoes or awkward shapes like that. Pluto and it’s “not quite planet” siblings are not roughly spherical, they are ugly shapes.

Anonymous 0 Comments

The planetary society came up with a set of rules for What Is A Planet and they say Pluto is too small with an erratic orbit so it is considered a Dwarf Planet.

Anonymous 0 Comments

Pluto was classified as a planet for many years. The issue was that additional bodies similar to Pluto were then discovered beyond Pluto. At some point the astronomical community felt they either had to choose between adding those other bodies into the solar system, or to delist Pluto from its planet status. They chose the latter. The things like distance, size and characteristic of its orbit are some of the main reasons to call it something other than a bonafide planet.

Ultimately, Pluto doesn’t care.