Why do the 9 planets orbit around the Sun?

[Robo]

Hi,

 

Why do the 9 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto) orbit around the Sun? If the reason is due to the fact that the Sun has the biggest mass, why wouldn't the planets get attracted toward the center of the sun, instead of orbiting around the Sun elliptically?

 

Furthermore, since Jupiter has a bigger mass than Earth, why is it farther away from the Sun than Earth?

[[Tycho?]]

Yes, the sun is signifigantly more massive than all the planets put together.

 

The planets are attracted to the center of the sun.

 

Because Jupiter happened to form further away.

 

Look up on google or wikipedia some basics, like definitions of orbits, keplers laws... that should clear up these misconceptions you have anyway.

[swansont]

Hi' date='

 

Why do the 9 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto) orbit around the Sun? If the reason is due to the fact that the Sun has the biggest mass, why wouldn't the planets get attracted toward the center of the sun, instead of orbiting around the Sun elliptically?

 

Furthermore, since Jupiter has a bigger mass than Earth, why is it farther away from the Sun than Earth?[/quote']

The central force of 1/r² form leads to elliptical orbits, with the sun at one focus. (Kepler's first law) More on elliptical orbits

 

They orbit because they have kinetic energy and angular momentum, and have to orbit, or else they would spiral in or fly away. The orbit depends on the speed and radius, and the relation between those two values is independent of the planet's mass - assume a circular orbit, and set the centriptal force equal to the gravitational force, which is a required condition for the circular orbit, and the mass of the planet cancels.

 

I think the mass of the planets depends on what mass was in the area to coelesce into the planet. It's possible that the earth would have had a large amount of gas around it as it was forming, but it was blown away by radiation pressure from the sun - I'm not a planetary formation expert, but that's implied here where it says "The Solar Wind blows out the Remaining Nebular Gases"

[DietAnthrax]

If you consider one planet in orbit around a star, what happens is that both orbit around the common centre of mass - the star can also be considered to be in orbit, albeit it moves around much less, because the common centre of mass is a lot closer to it, than it is to the planet. The Moon-Earth common centre of mass is located actually inside the Earth - the Earth "wobbles" around it. The same is true of the Sun.

 

Why do things orbit? Linear motion plus a force with a normal component to the linear motion gives elliptical motion.

[Orion]

According to the nebular hypothesis, this is the result of solar system formation. This model explains qualitatively many features of the solar system, including the fact that the planets essentially all revolve around the sun in the same plane.

[MD2576]

As planets gain mass would they not drift further away from our son as they gained more mass? Is this not why our moon drifts slowly away from the Earth? If it were gases and debris that slowly coalesced then it would slowly gain distance from earths gravity due to inertia?

[swansont]

As planets gain mass would they not drift further away from our son as they gained more mass? Is this not why our moon drifts slowly away from the Earth? If it were gases and debris that slowly coalesced then it would slowly gain distance from earths gravity due to inertia?

 

If the gained mass changed the angular momentum, e.g. an impact, then the orbit would change. But the orbital path is independent of the mass - it's the acceleration that matters, and that depends on the sun's mass, for a planet in orbit.

 

The moon is receding because of "tidal friction." The tidal bulge in earth means that it is no longer symmetric, and the deviation from a sphere that the bulge causes allows the earth to exert a torque on the moon (and vice-versa). So the earth slows down and the moon recedes. Angular momentum is conserved, since the torque is internal.

[MD2576]

How can orbital path be independant of mass? doesn't it take more gravity to hold a larger mass? If so much gravity holds a certain object at a certain distance from our earth then wouldn't adding more mass to that object make it harder for the earth to hold that object with the same amount of gravitational pull?

[Conceptual]

All the planets have the same spin direction. If one looks at weather systems, high pressure systems have clockwise spin due to the rotation of the earth and low pressure systems have counterclockwise spin due to the condensation of water. The high and low pressure systems attract each because their opposite spins are additive. The parallel spin of all the planets makes them subtractive or repulsive to each other. This would have repelled them early in their formation. Any additive spinning planets would have added or become attracted to other planets to form larger planets.

[swansont]

How can orbital path be independant of mass? doesn't it take more gravity to hold a larger mass? If so much gravity holds a certain object at a certain distance from our earth then wouldn't adding more mass to that object make it harder for the earth to hold that object with the same amount of gravitational pull?

 

Yes it takes a larger gravitational force, of F = GMm/r² But F=ma, so the force increases at exactly the same rate the mass increases. The mass of the satellite ends up not mattering.

[MD2576]

So more mass guarantees more gravitational pull or does more mass cause faster rate which guarantees more gravitational pull?

[swansont]

So more mass guarantees more gravitational pull or does more mass cause faster rate which guarantees more gravitational pull?

 

More mass causes a larger gravitational pull, and a larger gravitational pull is required.