My son came home with his solar system & only had 8 planets. I was taught Pluto is a planet he says it's not.

Question

Is pluto a planet or not? I looked it up on the internet & some say it is some say it isn't. It has been chaged to a dwarf planet is it a moon & all sorts of stuff. For my own peace of mind some one please tell me a correct answer to the question. Is Pluto the 9the planet in our solar system or not???

Answer 1

No, I'm afraid not. In a controversial decision last summer, the triennial meeting of the IAU (International Astronomical Association) voted to deny Pluto the title of "planet," basically because (1) it already stood out from other planets in having both a highly eccentric and highly tilted orbit, and also because (2) some even bigger objects have been found just beyond it in similarly unusual orbits.

They simply didn't want to expand the definition of planet to include all these extra bodies, so the decision, not reached without heated discussion, was to demote Pluto from its status as a genuine, major planetary body in our Solar System.

Sorry about that --- RIP Pluto!

Live long and prosper.

Answer 2

Is Pluto a planet???? Yes and no...

Well for starters, Pluto is just too small. In the neighborhood where Pluto lives? Planets are supposed to be huge. The Jovian planets, Jupiter, Saturn, Uranus and Neptune are 20 to 300 times the size of the Earth, and Pluto is really small compared to the Earth, smaller than our Moon. Kind of stands out.

And Pluto is not made out the same material as the Jovians. The large planets are mostly gigantic spheres of gas, mostly hydrogen and helium. Likely there are no solid surfaces, only denser and denser gas all the way in. Pluto is a small solid world of methane, water, carbon dioxide and ammonia ices, maybe a little rock and with a just hint of atmosphere (that freezes out and falls as snow in her "winter").

And third, Pluto's orbit is the most eccentric (oval shaped) and the most tilted to the plane that the rest of the planets orbit in. Also, Pluto is locked in a resonance with Neptune's orbit and comes closer to the sun than Neptune sometimes.

There were theories that Pluto was a lost moon of Neptune but that was before we discovered she a has one large moon (Charon) half her size (pretty much, this system is a double planet) and recently two other teeny-tiney moons (Nix and Hydra).

Pluto seems like she cant be an ejected moon-she must have formed on her own and seems to be part of an entire army of small icey-dwarf objects that circle just outside Neptune's orbit in what is known as the Kuiper belt. We have no idea of how many or how large these objects may be, hundreds???? NOT "planets" proper, hence the new term "dwarf planet" where Pluto is king.

But... I still think Pluto SHOULD be called a planet because of historical reasons (discovered by an American, financed by Percival Lowell, Tombaugh's life story, etc).

Answer 3

Pluto was discovered in 1930 and ever since then we have learned it as the "9th planet". However, Pluto has always been controversial as a planet. The reason for this has to do with several facts:

1) It has a highly "non-standard" elliptical orbit . . . it does not orbit in the plane of the ecliptic like the other 8 planets.

2) It is a rocky planet beyond the large gaseous planets of Jupiter, Saturn, Neptune and Uranus . . . this makes it a real "odd ball".

3) Other spherical objects, as large as Pluto, have been recently discovered beyond Pluto which had to have some sort of classification.

Because of these things, in August of this year, the International Astronomical Association, the standard setters of Astronomy, decided to redefine what a planet was. The part of the definition that knocked Pluto out of "planethood" was that Pluto did not clear its orbit (in other words, Pluto crosses the orbit of Neptune . . . twice). Since Pluto was also the "odd man out" they decided to downgrade Pluto to a category called "Planet-Like Objects". Now, or at least until they get enough complaints from the "Disney crowd", Pluto is no longer considered a planet.

If you are interested in more on this topic most of the science publications ran full stories on this just recently. Google Pluto, Planet, Planet-Like Object.

EARTH/SPACE TEACHER

Answer 4

IAU Decision



The debate came to a head in 2006 with an IAU resolution that created an official definition for the term "planet". According to this resolution, there are three main conditions for an object to be considered a 'planet':

1. The object must be in orbit around the Sun.
2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3. It must have cleared the neighborhood around its orbit.

Pluto fails to meet the third condition. The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as prototype for a yet-to-be-named category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.

Prior to this decision several other definitions had been proposed, some of which might have ruled out planetary status for Earth or Mercury or may have classified several of the asteroids as planets. This version was democratically chosen in a successful attempt at avoiding these non-traditional results.

Answer 5

Pluto is officially not a planet. My science textbook, however, was published when Pluto was. Still, it had a discussion in which it stated that a) all the other planets past the asteroid belt are gas giants, while Pluto is not, b) Pluto is too close to Jupiter and could thus be an escaped moon, and c) had an eliptical orbit and and was composed mostly of ice, where a planet would be composed of rock with a more circular orbit. It proposed that Pluto be the next category of planets called "ice planets, of which it was sure there would be more discovered. I, though I feel like an idiot for it, am still loyal to Pluto, and, believe it or not, have lost a little sleep over this issue. Apparently you have, too.

Answer 6

It has been ruled that Pluto is a minor planet. A minor planet is different than a planet and there are rules that I have read and immediately forgot. I believe the State of New Mexico just decided to declare Pluto a planet despite the ruling of those supposedly in the know. Even the discover of Pluto thought that it was a Kuiper Belt object. There are other "objects discovered out there that are larger than Pluto and have moons and it is predicted that there are lots more. Cute part-One of the new discoveries was nicknamed Zena and its moon was called Gabriel. The next one was called the Easter Bunny. Now they have proper names but its good to see that someone has a sense of humor. In trying to verify what I am telling you I cannot quickly find that information. But those that are in the know made some new rules and Pluto was out. I'm with New Mexico. Who cares? Leave it alone.

Answer 7

I was also taught that Pluto is the 9 the planet.Scientist in 2004 have discovered a 10 the planet even smaller than pluto.It should be called a dwarf planet but they say its our 10 planet.

Answer 8

On 8/24/06 the IAU (a group of astronomers responsible for naming objects) voted to downgrade Pluto to dwarf planet status. They have found other, larger objects near Pluto so instead of calling them all planets, they decided on the new category. The basis for the vote is that Pluto has not cleared away all objects near its orbit. So your son is correct that now there are only 8 planets.

Answer 9

Recently, the International Astronomical Union (..the folks that decide such things...) officially declared that Pluto is NOT a planet. Instead it's been downgraded to 'subplanet.' So, that leaves only 8 official planets in our solar system

Answer 10

Pluto hasn't changed at all. Only it's scientific classification was changed. Compared to the other planets, it's rather small and it's orbit is very tilted and off-center, kind of like those new planetoids, Sedna, Eris, Quaoar and such. So the astronomers decided to lump it together with the "new-comers", seeing as how there are likely to be a lot more of them discovered in the coming years.