Are all orbits the same shape?

Answer 1

Orbital shapes are conic sections.

A closed orbit is elliptical. That can include circular, but that's very unlikely, since the circle
is just an ellipse whose foci happen to exactly coincide.

An open orbit is hyperbolic. It can also be parabolic, but that's very unlikely, since the parabola
is just the exact boundary condition between closed and open orbits.

Answer 2

Kepler didn't 'discover' anything, and he didn't prove anything. He worked with

mountains of data, and found a theory that fit them best.

Tycho Brahe was a Dane who spent most of the nights of his life observing the

stars and the planets, measuring their positions, and keeping written records of

his measurements. Kepler had access to Tycho's notebooks, and used Tycho's

data to try to figure out how all of these things were situated and how they moved.

Remember that in Kepler's time, the question of whether the center of everything

was the sun or the Earth hadn't yet been answered to everyone's satisfaction,

and Kepler had to juggle that question too.

Kepler spent literally years with Tycho's measurements, trying one model after

another for how the set of planets was put together, looking for one geometry

that would fit the motions that Tycho actually saw. What he 'discovered' was:

If you assume that the sun is in the middle and assume that the planets revolve

around it in elliptical orbits, then that model fits Tycho's observations pretty well.

In his three "laws" of planetary motion, Kepler said: "Here's a model that does

a pretty good job of describing the motions we see in the sky, and here's how

the model is put together":

1). The planets revolve around the sun in elliptical orbits with the sun at one focus

of each ellipse.

2). The line from the sun to the planet sweeps out equal areas in equal periods of time.

3). (The square of the period of revolution)/(the cube of the average distance from the sun)

is the same number for every object that revolves around the sun.

Tycho spent most of his life gathering the numbers that Kepler worked with.

Kepler spent years of his life finding the three rules that make a model that

matches Tycho's numbers. And then, many years after Kepler passed on,

Newton came up with his law of gravity, and he showed that if gravity exists

and works according to his equation ... then gravity has to lead to orbits, and

the way the gravitational orbits work has to be . . . . . Kepler's laws !

Is that cool or what ! ? !

Answer 3

All orbits are ellipses, a sort of oval. Kepler's laws didn't give people enough information to actually calculate an orbit, but his work was fundamental to Isaac newton's work in developing theories of gravity and developing calculus.

Answer 4

They are shaped like ellipses with relatively low eccentricities.

That means a circle that has been slightly squashed.

Planetary orbits are nearly circles, slightly elongated, but the main thing that is noticeable is that the Sun is off-centre.

For example the Earth's orbit has a mean radius of 149.6 million kilometres but the ellipse is only squashed by 0.02 million kilometres, so it is almost a perfect circle. But the Sun is 2.5 million kilometres from the centre, therefore the distance varies over a 5 million kilometre range.

Answer 5

They're all elliptical.

We think of an "ellipse" as an oval shape. But there are ellipses that are

so slightly oval that you couldn't tell them from circles.

Also, mathematically, a perfect circle is just a special, unusual, kind of ellipse.

Answer 6

The planets orbit in an ellipse. An ellipse is described as a geometric shape where the sum of the distance from the foci at any point is the same. An ellipse has three main points. Two foci and a center like a circle. While a true circle has all its external points equidistant from its center, an ellipse measures its points from the foci, which are equidistant to the center point at on both sides.

The planets ellipse is closer to a circle than an all out ellipse, however, the orbit is still a true ellipse.

It is also true that the shape of a planet's orbit (an ellipse) is a conic section, i.e. the intersection of a right circular cone where the intersecting plane is not perpendicular to the cone's axis, but less than being parallel to one of the cone's nappes.

Answer 7

They are usually an ellipse, which is a regular oval shape.

Answer 8

An ellipse. All planets move around the Sun in ellipses.

Answer 9

Elliptical (eggshape) the gravitational pull causes this

Answer 10

Johannes Kepler discovered that planets follow elliptical paths.