Question about Pluto

[Ronnie67]

We know about the four gas giant in our solar system, but I was wondering about Pluto, since its just a small rocky planet, sorry dwarf planet, my question is was Pluto once a large gas planet like its neighbors those many billions of years ago and over time the gravitation pull of the much large planets ripped its outer layers leaving behind its inner core. Reason for my question is Earth, Mars etc the smaller planets are all solid but the outer planets, the giants are all gas apart from Pluto, so I was just curios to know why Pluto was so small.

[SirFoo]

Don't think so. Pluto is a Kuiper Belt Object. One of many ....just a bit bigger than most . They're all rocky/icy out there. Don't think they ever had a gasy atmosphere.

[Capricorn]

Pluto would never have been big, if it was then the gravity of it would have kept the gasses around it.

You are talking of gravitation forces from a body many millions of miles away stripping the gasses away from a centre of gravity of a few thousand miles. The others simply would not have any effect, they haven't stripped the earth of its atmosphere have they.

Why is it so small, it's a dwarf planet.

The planets are simply different sizes and I don't think pluto is the biggest of the dwarf planets either.

Meaning why pick Pluto out?

Really why are they in a pretty well ordered manner is the question, 4 rocky's planets then 4 gas giants and not a mix of rocky and gas. Suspect the sun is a factor, the wind from that will strip atmospheres off. However many exoplanets appear to be close to their suns and are described as super Jupiters - presume therefore gas giants.

[Ronnie67]

Thanks for that, I was just wonder why Pluto was so small compared to it larger neighbours

[VigdisVZ]

I'm sure you know much of this already, but I'm mentioning the background anyway:

Actually there is a whole plethora of trans-neptunian objects called the Kuiper belt and the Oort cloud.

http://en.wikipedia.org/wiki/Kuiper_belt and http://en.wikipedia.org/wiki/Oort_cloud

And pluto is just one of many similarly sized dwarf planets. I'm guessing there are just too scattered to clump up.

However there have been unproven theories about dark gas giants and even cold suns that orbit the solar system...

http://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)

http://en.wikipedia.org/wiki/Tyche_(hypothetical_planet)

I love this subject. The Kuiper Belt and Oort cloud is the new frontier. Can't wait until the New Horizons Probe gives us pictures of Pluto.

http://en.wikipedia.org/wiki/New_Horizons

[JulianO]

I think it's still poorly understood how planets form, we thought we had a reasonable idea, then along came "hot Jupiters" and all sorts of other anomalies from exoplanetary searches.

However there appears to be a sweet spot for gas giants to form. They have to be outside the frost line, so they can gather ices and cold gas without them boiling away, also far enough out so the solar wind doesn't remove the accreted components as fast as they are attracted.

They also need to be near enough to the sun so there is lots of nebula stuff nearby that they can pick up. So near enough to pick up stuff, and far enough away that the material is cold enough.

Out near Pluto there is not much stuff it can pick up - its so spread out its difficult to get near enough to accrete extra stuff to make big planets.

There is also the whole area of planetary movement, it is unlikely Jupiter formed in it's present orbit and more likely it formed perhaps closer in and then got moved out by processes, and the outer planets are thought to have undergone even more extreme movement.

[cowasaki]

I agree there have been a number of theories about planetary formation over the years and all of them seem to answer the questions posed by the previously held theories. I think that there would not be too many arguments about pluto though, it is just simply an object from the Kuiper belt which has ended up in an altered orbit in and out of Neptune's orbit. Pluto isn't even the largest drawf planet at least one other Kuiper belt object is larger.

[Matt Scunthorpe]

Another thing to possibly bear in mind is the exoplanets are called 'super Jupiters' mainly because of their size. I'm not sure theres any actual evidence that they are Gas planets apart from the assumption because they are larger than Jupiter and Jupiter is made of gas. Its highly likely they are gas planets, but without taking a spaceship or getting a super powerful telescope to watch a transit and measure the atmopshere, i dont think we know.

Does anyone have any webpage links on this to prove me wrong? Would like to know more about this.

[JulianO]

Depending on the mechanism used to detect the exoplanets you can find out quite a lot about them. Their mass, their period and even their radius. Anyway, if you have their radius and mass, you can work out the density, and that tells you if they are made mostly of gas, or mostly of rock. Most are made of gas.