Pluto and Neptune

[Theslowone]

Just thinking about astronomy and thought of Pluto and Neptune crossing paths, I know that they are usually far away from each other but what is to stop them from colliding? I have read that Pluto has a 17 degree tilt and that stops it from colliding with Neptune, but how can it have a tilt and the paths never cross. And some people believe that Pluto had a sister planet that is now triton, one of the moons of Neptune. I realize that gravity of a large planet is great enough where close doesn?t have to mean very close but that still means, if it is true, that they got close enough back long ago.

Just looking for some insight.

 

[Cogman]

Kindof Confused on the second question. But for the first one. The reasion they never actually hit each other is because their paths dont actually cross (in a sence that they would be heading towards the same space in space ) You need to take a look at the orbital patterns, because I really am at a loose of how to explain why they don't (haven't) hit other then that. Also, scientists are debating whether or not Pluto is a real planet or just a chunk of Ice that somehow got caught in a strange orbit. Now if you want a really good question. Do you think it is possible that there are more then 9 planets orbiting the sun, I mean, we could be just looking at the wrong planes. All the planets that we have found right now have been on a fairly flat plane, but what if there are some others that we just have missed .

 

[iuvas]

They don't actually cross paths.

Take a look at this diagram

Notice on the bottom image that Pluto crosses the plane of Neptune?s orbit right in the middle of its orbit, like an "X". Now notice in the top picture that Pluto is only closer to the Sun at the very end of its orbit.

Basically, at the point where Pluto crosses Neptune?s plane, its orbit is much wider.

 

[sao123]

To answer your 1st question...

Dont think like the solar system is flat and planar. Because of the 17degree tilt of plutos orbit, Pluto crosses neptunes orbit at some distance + or - Z from the neptune orbit horizon. So they never actually cross paths or even close.

However...theres even more....here's a quote from
http://www.xs4all.nl/~carlkop/plutino.html

"Plutinos", meaning "little Plutos", is a generic name given to the class of Kuiper Belt members with orbits that come very close, and sometimes even cross, the orbit of Neptune. Despite their often extreme proximity to Neptune's orbit, the plutinos do not in fact have the possibility of encountering Neptune itself, because the periods of revolution about the sun of the plutinos and Neptune are precisely in a ratio of three to two. This means that, after three revolutions of Neptune and two of a plutino (about 500 years), the relative positions of the objects in their orbits repeat, and this cycle does not give the bodies an opportunity to pass within 10 or more astronomical units of each other. Although the cycle may break down eventually, it seems likely that it will continue to repeat for perhaps tens or hundreds of millions of years, thereby preventing devastating encounters between a plutino and Neptune. Pluto, a 2400-km object discovered in 1930, has been known since 1964 to exhibit precisely this type of motion, and it should therefore be considered as the first known member of the Kuiper Belt; the second member of the group would then be Pluto's satellite Charon, discovered in 1978 and having about half the diameter of Pluto.

The plutinos contrast with what may be called the "cubewanos", in recognition of their prototype 1992 QB1, also discovered by Jewitt and Luu. Cubewanos, which comprise perhaps 60-70 percent of the known objects in the Kuiper Belt, travel in orbits that are substantially more nearly circular and closer to the plane of Neptune's orbit than the plutinos. And whereas the plutinos orbit the sun at an average distance of 39 astronomical units, cubewanos have average distances over the range 42-46 astronomical units. They are therefore well beyond Neptune at all times.

Let me also suggest you read the entire article about the kuiper belt which really describes what you are asking about more than just pluto/nepture, but all the planets in that belt orbit...
http://members.lycos.co.uk/JeremyBatterson/kuiper.html
and
http://cse.ssl.berkeley.edu/SegwayEd/lessons/cometstale/com3_a.html

And read about another "theorized" belt called the Oort Cloud which may be even further out, but have similar properties to the kuiper belt. BTW. Most comets are theorized to have originated from either the kuiper or Oort belts.
http://seds.lpl.arizona.edu/nineplanets/nineplanets/kboc.html

Do you think it is possible that there are more then 9 planets orbiting the sun, I mean, we could be just looking at the wrong planes. All the planets that we have found right now have been on a fairly flat plane, but what if there are some others that we just have missed.

I once thought about this theory. However after having discussinos in the thread "what if the moon went away"
http://forums.anandtech.com/messageview.cfm?catid=50&threadid=915890&FTVAR_MSGDBTABLE=arc
I realized that the sum of all the gravitational pulls (and the resulting force moments) must be balanced at all times or else the sun would develop a wobble (think about an unbalanced tire), which would evenually eject planets from the solar system rapidly. I believe that someone had calculated a theoretical limit for the max angle from the horizon that a planet could have and still effectively orbit the sun without imbalance.

 

[TenaciousT]

A good site for nifty astronomy information (which includes the debunking of common myths) is "Bad Astronomy".

Check it out.

 

[StrongShock]

sao123 is correct. from what we know, pluto & neptune will not cross paths. that diagram on dosxx doesn't state whether it views from the x or y. however, i know that the perigee of pluto (part of orbit nearest the sun), where a projection to the x-y plane of both planets paths meets, does occur near the maximum displacement from the solar plane (plane in which earth & most other planets rotate).

one thing nobody has accounted for is the orbital precession of pluto. the fact that no planet is fully symmetrical or homogenious means that, the slight difference in mass distribution about a planets rotational axis oscillates within the central bodies gravitational field. the same can be said for the sun, which has a very dynamic mass distrubution to begin with. the result is a slight instability in both rotation and orbit, which can cause the orbital and rotational axis to shift inertially. this means that trillions of years from now, pluto's orbit could align with neptune & the two could possibly collide.

no numeric analysis that i know of could prove or refute claims of such events in the distant future, since there are many unknown variables & our measurements lack the required precision. however, it is possible. in fact, in my senior project we designed a constellation of satellites that, without very expensive orbital maintenance propulsion, would be in danger of loosing the required period of sun to recharge themselves due to orbital eccentricity & precession.

*snore*

 

[PowerEngineer]

Originally posted by: Theslowone
And some people believe that Pluto had a sister planet that is now triton, one of the moons of Neptune.

I've heard some astronomers speculate that Pluto might have started out as a moon of Neptune that was then "liberated" by some gravitational disturbance long ago.

 

[Theslowone]

Thanks for the responses, I figured the what you all stated but all the sites i visited just seemed to tip toe around the answer.

 

[grrl]

Originally posted by: PowerEngineer

Originally posted by: Theslowone
And some people believe that Pluto had a sister planet that is now triton, one of the moons of Neptune.

I've heard some astronomers speculate that Pluto might have started out as a moon of Neptune that was then "liberated" by some gravitational disturbance long ago.

Wouldn't that also help explain its tilted orbit?

 

[Chaotic42]

Originally posted by: grrl


Wouldn't that also help explain its tilted orbit?

It also could have been hit by something, like a comet, or it could have been nicked by Charon (wherever it came from).

I don't think we'll know until we go there and set up a research facility. We'd have to compare it's composition to that of other likely origins.

 

[sao123]

Not that it explains why plutos orbit is different, but it isnt alone.

Pluto is a member of the kuiper asteroid belt, called the plutinos. They all share a similar orbit similar to pluto. Tilted. Elliptical.

I really like this article here...read the entire article. long but full of good information.
http://members.lycos.co.uk/JeremyBatterson/kuiper.html