planet's orbit is elliptical,why?

Question

wHY all planets revolVE AROUND THE SUN IN ELLIPTICAL ORBIT?

Answer 1

Planets don't orbit the sun.

Ok, that's a smart @$$ answer, but they don't. Let's look at a simple two body system, one sun, and one planet, and ignore the effects of coalescence (That is, how the sun and planet formed in the first place). Now gravity works both ways, the sun pulls on the planet, and the planet pulls on the sun. If they start out stationary, they will pull together and slam into eah other (not fun). If they're in motion (an effect of coalescence from the accretion disk), then they're moving relative to each other (yeah!). If the sun and the planet happen to be of the same mass, they move in a circular orbit about a center exactly half way between them. This is called the center of mass. In general, the center of mass is a point that is proportional to the ratio of the masses of the objects. Now lets pretend the sun is MUCH more massive than the planet. The center of mass of the system is much close to the sun than the planet, but not exactly at the center of the sun. Both the sun and planet are in a circular orbit about this center of mass. Now change reference frames, and make the sun the center of your reference frame. In this case, it would look like the sun was not rorbiting anything, and the planet was in an off center circular orbit (a type of ellipse) in which it was closer to the sun at one point, and further away at another. Now add another planet to the mix (things get real fun now!!!). The center of mass is no longer constant. It moves in relation to the movements of the two planets. Now remember that gravity works on EVERY massive object, so planet 2 is pulling on planet 1, and vice versa. This perturbs the off-center circular orbit into an elongated ellipse. Add more planets and the shape of the ellipse changes, and begins to perturbate (that is the major and minor axis rotates).

Answer 2

The path of an orbiting body is defined by an orbit equation. If you do the maths for a body orbiting under the effect of gravity there are four possible shapes - circular, elliptical, parabolic or hyperbolic. If the shape's parabolic or hyperbolic then the orbit's open and the orbiting body doesn't come back, so a planet has to be in either a circular or an elliptical orbit. Most of the planets' orbits are nearly circular, but the chances of an orbit being perfectly circular are very slim!

Answer 3

Actually, parabolic and hyperbolic "orbits" are possible, as well.

The shape of the orbit of any object (planet, comet, dust grain) around any other object can be calculated given the initial positions of the two objects and their relative speeds, because we can calculate the force of gravitational attraction between the two objects. Because the force of gravity is inversely proportional to the square of the distance between the two objects, any conic section (ellipse, parabola, hyperbola) is a possible orbit. The math works out that way.

Kepler first realized that the orbits of the planets were ellipses rather than circles, but he didn't know why. It wasn't until Newton came along with his Universal Law of Gravitation that we found out the possible shapes for orbits.

BTW - a circle is a special case of an ellipse, and there are moons that have circular orbits around their planets. None of the planets have circular orbits, however, in large part because they are tugged (gravitationally) by the other planets, so their orbits remain elliptical.

Answer 4

The elliptical orbit, with the Sun at one focus, is the solution that comes from having an inverse-square force law, like Newtonian gravity.

One way of thinking about this is: an ellipse is the most general closed curve that is generated by an equation that is second-order in the variables (that is, contains the position variables, the squares of the variables, and constant terms). The inverse-square law leads to second-order terms and no third or higher order terms. So closed-orbit solutions must be elliptical.

In Einstein's General Relativity, the force law has some small higher-order terms in addition to the large inverse-square term. This means that the orbits are, in fact, not exactly elliptical. You can think of them as ellipses that do not quite close, or ellipses that rotate (precess) in time.

Answer 5

There may be such objects, and if they are discovered the IAU will have to come up with a term for them. No moons of moons are known so far. In most cases, the tidal effects of the primary planet would make them unstable. However, calculations performed after the recent detection of a possible ring system around Saturn's moon Rhea indicate that Rhean orbits would be stable. And the suspected rings are thought to be narrow which is normally associated with shepherd moons. And they have already found moons orbiting objects that are not planets. An asteroid moon is an object that orbits an asteroid as its natural satellite. It is thought that many asteroids may possess moons, in some cases quite substantial in size. Pluto and Eris are dwarf planets, and they have moons as well (still referred to as moons).

Answer 6

At any given distance there is only one exact speed that will result in a perfectly circular orbit. If the planet is going any slower, it starts to fall toward the Sun and if it is going any faster it starts to fly out away from the Sun. Assume it is slow and starts to fall toward the Sun, it will speed up as it falls. Eventually it ends up closer to the Sun but going to fast, which causes it to fly away. But as it files away, it slows down and ends up farther away and going too slow, so it falls back again. This repeats forever to make an elliptical orbit.

Answer 7

i'm not sure, but i think that along with gravity, the sun or any other planet has a magnetic field, so that if the opposite poles of bodies would come together, there would be more attraction than when the poles are not magnetically connected. so i think thats why orbits of planets are elliptical.

Answer 8

They follow the gravitational field of the sun, in a constant, efficient way. It took time, but due to the suns great mass & energy we ultimately moved into this system.

Answer 9

it is the laws of gravity
read keplers theory