Celestia Forums

Well, I was just wondering if it would be possible to place an object in a stable perpendicular orbit about the sun (in relation to the solar plane)? Also what the limits of distance be (closest to the sun and furthest from the sun) for various orbits?

I suggest you check out Gravity Simulator: the problem of stable orbits is really complicated so simulation is probably the best way to proceed.

The program comes with a solar system simulation, so you'd just need to add in your object and see what happens.

I suspect that perpendicular orbits are likely to be unstable, though I'm not entirely sure whether the Kozai mechanism would apply in this case.

What I'm after is a way to 'hide' a space station or some such, and North or South of the Solar Plane just seemed logical at the time. However then I started thinking that if all the planets are (roughly) orbiting on a plane and the sun revolves on the same plane, then there must be something unstable about other configurations, but wasn't sure.
Thanks.

You can't hide anything north or south of the ecliptic plane, whatever your orbit it has to cross the ecliptic. There are stable orbits outside of the ecliptic, a good example is Puto with a 17?° inclination (Pluto is locked in a 3/2 resonnance with Neptune).

Most comets or Kuiper objects are not in the ecliptic, but most of them are relatively close to it. See 2004 XR190 for a counter example.

Thurlor wrote:What I'm after is a way to 'hide' a space station or some such, and North or South of the Solar Plane just seemed logical at the time. However then I started thinking that if all the planets are (roughly) orbiting on a plane and the sun revolves on the same plane, then there must be something unstable about other configurations, but wasn't sure.
Thanks.

Who or what are you trying to hide it from...Earth? - There is a libration point behind the Sun which cannot be seen from Earth, also behind the moon)
Read about Lagrange points here: http://en.wikipedia.org/wiki/Lagrange_point

Read about "Counter Earth" here: http://www.vectorsite.net/tpecp_06.html and here: http://en.wikipedia.org/wiki/Counter-Earth

If all you want to do is make an object stay in one place over the pole, you can do this in Celestia like this:
Of course, this is not actually possible in reality.

Actually I'm trying to 'hide' a rogue space station from the solar system in general ( a futuristic scenario). If it were only hiding from Earth it would be easy to put it behind the moon or sun relative to Earth, however it has to hide from most pf the planets.
I realize that any perpendicular orbit will have to cross the ecliptic plane twice, but that's still got to be better than always being one the ecliptic plane.

Don't forget, of course, there's stability and then there's stability

If it's invaders, they probably wouldn't care if the orbit gets disrupted after a few hundred years. By that time they'll probably have succeeded or given up.

As Chaos suggested, the gravity simulator program is one way to find out if an orbit will last long enough.

Chuft-Captain has suggested some good hiding points. Earth's L3 and the Moon's L2 aren't stable, but only minor correction burns can keep you there indefinately. Of course you're not invisible to an interplanetary spacecraft designed to look for you.

Christophe is right. Even a polar orbit has to cross the ecliptic. And even while its high above the ecliptic, it's not invisible to a telescope pointing that direction. I've heard that Xena (2003 UB313) wasn't discovered sooner because of its high inclination. Nobody was expecting something in an orbit with such a high inclination (~45 degrees). But... Xena is currently somewhat close to its ecliptic-crossing position. It's currently in the constellation Cetus, with a declination of -5.5 degrees. So this excuse confuses me.

I don't know why you couldn't have a stable polar Solar orbit, unless your orbit had a huge semi-major axis that placed it beyond the Kuiper Belt. The Kozai Mechanism would prevent you from having a polar Earth orbit. The plane of your orbit and the plane of the Earth's orbit would be 90 degrees. However, polar low-earth orbits are safe, at least on short time scales. Close to the Earth, the Earth's gravity is very overwhelming, making the Kozai Mechanism insignificant. But the Sun orbits the galaxy. And the plane of the planets and the plane of the Sun's orbit around the galaxy are different. This is the type of thing the Kozai Mechanism likes to pick on. But relative to the size of the galaxy, the planetary region of the solar system is small (equivalent to low-earth orbit satellites), and is spared from the Kozai Mechanism.

If the Sun happens to have a massive companion, Nemesis as some call it, then the Kozai Mechanism would become significant at distances just beyond the Kuiper Belt.

So, who are you hiding from?

Might want to explain what the "Kozai Mechanism" is... I've never heard of it and I've done some orbital dynamics in my time...

Just a thought...

I overlooked where you said you wanted to hide from all the planets.

You could orbit the Sun interior to Mercury. It's a futuristic space station, so shading themselves from the Sun wouldn't be difficult. Your spacestation would be lost in the solar glare as viewed from every planet. And you'd have an awesome view of all the planets.

Malenfant wrote:Might want to explain what the "Kozai Mechanism" is... I've never heard of it and I've done some orbital dynamics in my time...

If you Google or Yahoo it, my website is first . There's an explanation that attempts to sum it up in laymans' terms, and a few diagrams. But you'll probably want to read the additional Google entries... the ones written by real scientists.

tony873004 wrote:You could orbit the Sun interior to Mercury. It's a futuristic space station, so shading themselves from the Sun wouldn't be difficult. Your spacestation would be lost in the solar glare as viewed from every planet. And you'd have an awesome view of all the planets.

That's a good idea.
...and you could attack any planet you liked by coming out of the sun (in the age old tradition of aerial combat!)

Who do I want to hide from?

Well, this is all for a Novel I'm working on (planning) and I was working with the idea of the occupants of a human base somewhere in the solar-system being the only survivors after Earth (and it's other outposts) are wiped clean of life by aliens.

I really like the idea of launch an attack with the sun behind you. Thanks Chuft-Captain. However, it would also reduce the area in which to search for the base.

Thurlor wrote:Who do I want to hide from?

Well, this is all for a Novel I'm working on (planning) and I was working with the idea of the occupants of a human base somewhere in the solar-system being the only survivors after Earth (and it's other outposts) are wiped clean of life by aliens.

I really like the idea of launch an attack with the sun behind you. Thanks Chuft-Captain. However, it would also reduce the area in which to search for the base.

But the aliens wouldn't know to look there until an attack was under way.

As I was trying to imply. A one time only advantage, though still better than nothing.