Planetary orbit and spin in our solar system (please see details)?

Question

This is not a homework question - this is just out of curiousity.

Why do the eight planets in our solar system orbit the sun in the same plane? (The newly demoted Pluto is also "close", orbiting slightly off of this plane.)

Is there a meaningful relationship between the sun's equator and the plane of the orbiting planets?

Why are the spins of these planets also the same (they all spin in the same direction as earth and not the opposite)?

Do other solar systems in the universe exhibit the same phenomenon described above?

Answer 1

The answer to your question lies billions of years in the past before our solar system had formed. At that time an immense cloud of gas and dust drifted in interstellar space. Within this nebula were regions of higher density, and in one of them the gas and dust began to accumulate into individual objects. Also within this region there was random motion that was transferred to the developing spheres (..conservation of momentum). As more and more material was acquired by the proto-planets and sun, the developing solar system formed itself into a disc because it took on more and more of the original nebula's motion, thus the velocity of the disc increased, and that led to a disc that was progressively flatter and flatter.

Today most of the planets of our solar system orbit the sun in almost the same plane (..called the 'ecliptic') with Venus and Pluto the most notable exceptions.

Answer 2

When the "cloud" of gas and dust collapse, under its own gravity, to form the Sun and the Solar system, it was already spinning: the spinning shaped it into a disk. That is why all the action is confined to a disk region (now called the "plane").

During a project I did last year (observing the surface of the Sun and charting the movement of spots), I was surprised to learn that the Sun's equator does not match the plane (there is a difference of approx. 8 degrees between the plane of Earth's orbit and the Sun's equator).

The orbits of all planets are "prograde" (same direction as the Sun's spin). The spin of the planets is not all prograde: Venus is spinning very slowly in the other direction and Uranus is spinning on its side.

Answer 3

The planet Uranus actually has its south pole pointed to the sun, and I've always wondered why. What could knock a planet on its side?

As far as other stellar systems, I don't think we know enough yet to say one way or another. We are just now starting to find gas giant planets around other stars. Should be interesting in the next few years as our technology gets better and better.

Answer 4

I have to dissagree most planets dont orbit on the same plane.

Answer 5

Momentum. The world has been rotating since the gases coalesced and condensed into a planet. It revolves around the sun for the same reason, and the sun revolves around the core of the galaxy for the same reason.