Why is the orbit of the planets in our solar system elliptical?

Question

Why is the orbit of the planets in our solar system elliptical?

Answer 1

Because our sun is elliptical, making it's gravity field elliptical.

Answer 2

This is still being debated by scientist. No one knows for sure. The earth had a geo centric orbit around the sun until 180,000 years ago, then it suddenly became an elliptical orbit.

No one knows why for sure.

Answer 3

Elliptical orbits are the "easiest" kind to make.

If you take a rock and place it at a random distance away from the sun, and then launch it in a random direction at a random speed, the laws of gravity say that one of 4 things can happen:

1. If you launch it very, very slowly and/or aim it almost exactly at the sun, it will crash into the sun.

2. If you launch it EXACTLY at right angles to the sun, at EXACTLY a certain critical speed "Vc" (which depends on the distance from the sun), it will go in a circle.

3. If you launch it at a speed greater than 1.41 × Vc (in nearly any direction), it will escape the sun's gravity and fly away forever.

4. If you do ANYTHING ELSE, it will fall into an elliptical orbit.

So, it really boils down to the laws of probability.  Cases 1 and 2 require very precise conditions, so the odds are that most random rocks will fall into Cases 3 and 4.  Rocks that fall into Case 3 are never heard from again; so virtually all rocks (planets, etc.) that remain in orbit around the sun fall into category 4.

Answer 4

i dont believe it look elliptical. it will look circle if youre from another solar system, but that solar system must be vertical and our solar system must be horizontal. as RickB  explain, i remembered when i was a kid, i used a rock throw in water at every differences angles and in fact  each different angle make the orbit look different. But Mr: RichB, sometimes it doesnt work out that way.. update your equation to new model..or it will get old as we get futher in the universe space. anyway because the gravity force had no mass in the universe, LOOK every planets is floating!!!!but can make a force!!!!!! watch out what i mean by this. do your recalculation again Mr:RichB.

Answer 5

Haven't you heard of the Kepler problem in general relativity? In the absence of any other forces, a planet orbiting a star under the influence of Newtonian gravity follows the same perfect ellipse permanently. The presence of other forces (such as the gravitation of other planets), causes this ellipse to rotate gradually.

Answer 6

given that there are so many forces tugging on everything, a circular orbit is basically impossible,

Answer 7

The orbit of planets lie on the geodesic which is the straightest path along curved space.  The orbit of the planest are elliptical because the sun is not the only center of mass in our solar system.  The geometry of the ellipses are so that the sun lies at one focus and the combined vectors of the masses lie at the other focus.  But this focus is ever changing as the planets move, therefore the elliptical paths are complex.  

Answer 8

Not all of the orbits are exactly in the same plane and most are nearly circular.

Some years back I was having fun with the new high-powered graphics available on PCs (yeah, VGA graphics LOL.  Better than the very old CGA graphics) and tried shooting an object into orbit around a gravitational force.  Never did succeed in obtaining a circular orbit.  All ended up elliptical.

One theory of the formation of the planets would have the cloud of gas surrounding the newly formed sun (condensed from gas - mostly hydrogen) slowly condensing into clumps of matter.  One thought on the start of the condensing is from static electricity as gravity would be almost negligible with very small particles.  As particles collided, gravity would hold some clumps together.  Sometimes they would collide with larger clumps.

Now I will warn you this is my conjecture here - those collisions would result in small 'pushes' to the newly formed larger clump which would retain the vector sum of the velocities of the particles which collided.  This would inevitably result in something other than a perfect circular orbit.

In any case, check this URL for some reading:

http://www.nineplanets.org/overview.html

You'll note that most orbits lie close to the same plane and most are *nearly* circular (but not exactly).

Notice that the orbits run about 7 degrees from the sun's equator.  I'm not sure why, but I would have assumed (dangerous for someone not highly educated in astronomy) that the ecliptic would lie very close to the plane of the sun's equator simply because of gravitational effects of the sun's rotation over the gas cloud for millions of years.

I'd love to hear more about that from someone who might shed some light on the subject.

Best regards,

Jim