Why is pluto a dwarf planet?
Pluto is smaller than 7 of the moons in the Solar System. Because it is so small many scientists don't consider it a planet at all. In 1999 a group of scientists attempted to redesignate Pluto as a comet. On August 24th, 2006 Pluto's status was officially changed from planet to dwarf planet. The reason Pluto was demoted is because in 2006, the definition of a planet was changed: The definition of "planet" set in 2006 by the International Astronomical Union (IAU) states that in the Solar System a planet is a celestial body that: 1. is in orbit around the Sun, 2. has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and 3. has "cleared the neighborhood" around its orbit. Is Pluto in orbit around the Sun? Yes. Does Pluto have sufficient mass to be nearly round? Yes. Has Pluto "cleared the neighborhood" around it's orbit? NO. Had this new definition not been made, then there would be 13 planets. Instead, now there are 8 planets and 5 dwarf planets.
Pluto; Planet, Dwarf Planet, or what?
Should be called a dwarf planet in my opinion. One of the supporting reasons is that recently several objects the size of Pluto (one is even bigger, i think) have been found out in the outer regions of the solar system. And it looks like there may be many more, including smaller but similar bodies. The choice came down to adding many new planets--all of which were quite small and remote--to the list of planets, or reclassifying them as something else. This is similar to what happened when scientist started finding asteroids in the asteroid belt. First they found Ceres, which was the biggest, but quite small by planetary standards. But then they started finding more and more, until there were thousands, with most being too small to really call planets. That's when scientists decided it made more sense to reclassify them as asteroids then to add thousands of new, tiny planets.
Is Pluto a star or a planet?
Neither. It’s a planetoid. It’s smaller than our moon, for crying out loud. How could anyone, in good conscience, call it a planet?You see, we don’t have an official technical definition of “moon”. We didn’t have one for planet as well, until in 2006 the International Astronomical Union came up with one[1] just to address the problem with Pluto. In order to be considered a planet, it has to meet three criteria:is in orbit around the Sun,has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), andhas "cleared the neighborhood" around its orbit.1. Check.2. Check.3. Nope! It’s still floating around the large Kuiper belt, it hasn’t cleared up jack sh!t.So, deal with it. Pluto isn’t a planet.Of course, it also isn’t a star. A star (although we don’t have an official definition for that either) is generally assumed to be massive enough to start a fusion process in its core. Pluto definitely isn’t that massive, like, at all.Footnotes[1] IAU definition of planet - Wikipedia
Is Pluto a star, moon or planet?
Let us first understand the basics of what is a star, moon, planet (and dwarf planet).Star: A ball of gas of such a mass that, when compressed by gravity will generate energy due to atomic fusion, and therefore generates light. They are fixed at a point, i.e. they do not revolve around the Sun like planets (Sun in itself is a star). Stars twinkle in the sky and are bigger in size / far away.Pluto does not qualify for a Star, since it is not a ball of gas, does not generate energy due to atomic fusion, or generates light of its own (It reflects lights that it gets from the Sun). Also, it does not have a fixed position and revolves around the sun (a star).Planet: An object in orbit around the Sun that is large enough (massive enough) to have its self-gravity pull itself into a round (or near-spherical) shape. In addition a planet orbits in a clear path around the Sun. If any object ventures near the orbit of a planet, it will either collide with the planet, and thereby be accreted, or be ejected into another orbit.Pluto does not qualify as a Planet, since Pluto had inability to clear its orbit of debris (pics via Monkeysee and Wiki) and has asteroids / rocks around it (the last criteria for an object to be a planet). Eris (Year 2005) bigger compared to Pluto was discovered, so the question arises what is the definition of the true planet and it was demoted in the year 2006. Also, It is 2/3 of the size of our Moon.Moon: A rocky celestial body (natural satellite) that orbits, mainly, a planet. Big planets may have moons that, if it orbited the star, would be considered a planet.Pluto does not qualify as a Moon, since it does not orbit a planet which in turns orbits the star (our Sun).Dwarf Planet: A dwarf planet is a planetary-mass object that is neither a planet (like Neptune) nor a natural satellite (like Moon). That is, it is in direct orbit of a star, and is massive enough for its gravity to crush it into a shape usually a spheroid, but has not cleared the neighborhood of other material around its orbit. This definition was was adapted in the year 2006 by IAU (International Astronomical Union) after considering other similar dwarf planet objects. Ceres and Eris are also a part of Dwarf planet.Note: My answer might be slight here and there in explanation. I hope, I am able to clarify the difference.Hope this helps!
Is Pluto now also considered a dwarf planet?
Pluto is a Dwarf Planet (not Drawf, as the question currently states), because back in 2006 the International Astronomical Union (IAU) realised there was a problem.First of all, you have to realise that “planet” is an entirely human category - the universe doesn't care, there are just rocks and piles of gas of varying sizes.For human convenience we label things as “planets” or “stars” or “asteroids” to enable us to talk clearly about them.But the problem is, that several things that were traditionally called Planets - such as Pluto, and Mercury, to a lesser extent - look a lot less like planets than other things out there.Pluto’s moon, Charon, is pretty much the same size as Pluto (within an order of magnitude) - so if Pluto is a planet, why not Charon?Then you've got the fact that Earth's moon is the same size as Mercury, and much bigger than Pluto. So why is the Moon not a planet, when Pluto is?Then you've got hundreds of things which are bigger than asteroids, but smaller than planets in the asteroid belt - Makemake, Ceres and so on - which are all pretty much the same as Pluto.We were therefore faced with a choice - we needed to draw some lines as to what makes a planet a planet.We could either make everything which is like Pluto a planet - and gain 5 or 6 planets - and the Pluto/Charon system would become a binary planet system. This seems a bit overkill! These things don't really resemble the other planets - so widening our definition just means the word “planet” conveys less information.The other option is to tighten the definition. Mercury stays a planet because it has “cleared its orbit” - ie there are no other dominant bodies nearby. The moon isn't a planet, because it isn't the dominant body - but Earth is.Sadly, this definition excludes Pluto - for the same reason that if Charon was upgraded, they'd be a binary system - they're just too similar bodies.For all intents and purposes, if you call Pluto a planet, people will know what you're talking about - but just as a banana is “technically” a herb - Pluto is not “technically” a planet.Whether you agree with the decision or not, that's the decision that was made - and so that's the convention that we stick by, or else everyone would be using a different definition!
Why is Pluto considered a dwarf planet?
It has not cleared it's orbital path of other objects. It is simply one object of many in what is called the Kupier belt. Think of the many objects in the asteroid belt between Mars and Jupiter. The Kupier belt is similar except these objects are icy. Pluto was mistakenly named a planet when it was first discovered. It was thought to be the size of Mars. We now know that this was because of the icy reflection from Pluto. It turned out to be much much smaller in reality. Although size has nothing to do with being called a planet, if we knew the actual size of Pluto when it was first discovered, it probably would never have been called a planet in the first place. It was a mistake that was finally corrected in 2006 by the International Astronomical Union.
Why is Pluto considered as a dwarf planet?
It *is* in our solar system... and, it was re-classified to be a Dwarf planet when a couple of other Pluto-sized masses were discovered. There can up to *50,000* of these objects in orbit about the sun - and, if Pluto was classified as a 'planet' still, that means there'd be up to 50,000 planets that would require names (and remembering all those names...) It was easier to reclassify Pluto for what it is - the first Kuiper Belt object of many to be discovered....