# Is the Sun spherical or oval?

• brum

#### brum

is the Sun a sphere (like the Earth) or is it more oval-shaped and elliptical?

because, since the Earth is (nearly) spherical, the moon has a (nearly) circular motion.

BUT, many (if not all) of the planets in the solar system have ELLIPTICAL orbits. This leads me to believe that the Sun is NOT SPHERICAL (!) but instead more shaped like an ELLIPSE.

(I always thought of the sun as pretty much spherical).

Is this correct?

You seem to be confusing two different shapes. Planetary orbits are in general elliptical, some more than others. The planets themselves, as well as the sun, are roughly spherical, somewhat flattened at the poles because of rotation.

The Sun is an oblate spheroid. Its shape is caused by its rotation, as mathman explained.

The word 'ellipse' describes a precise curve in two dimensions. It is not correct to say that a three-dimensional body is elliptical. The words for "stretched" spheres are "oblate spheroid" and "prolate spheroid," referring to spheres squashed at the poles or around the equator, respectively.

The movement of the planets and the shape of the central mass are not related. The shape of the Sun is unrelated to the shapes of the orbits of the planets. The shapes of the orbits of the planets are unrelated to the shape of the Sun.

When you're far away from a mass, the mass acts gravitationally as if it were concentrated in a point. As far as the planets are concerned (since they're far away from the Sun), the Sun is just a point mass. As far as the Moon is concerned, the Earth is just a point mass. The planets follow elliptical orbits, but it has nothing to do with the shape of the body they're orbiting.

You can solve Newton's universal law of gravitation (F = G (m1 m2) / r2) to discover that bodies orbit in curves described by conic sections (circles, ellipses, parabolae, and hyperbolae) with the center of mass of the system at one focus.

- Warren

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Originally posted by chroot
The word 'ellipse' describes a precise curve in two dimensions. It is not correct to say that a three-dimensional body is elliptical. The words for "stretched" spheres are "oblate spheroid" and "prolate spheroid," referring to spheres squashed at the poles or around the equator, respectively.
- Warren

Yeah I realized that (about an ellipse is only 2D) but I didn't know the name for its 3D counterpart, so I just used the word ellipse for simplicity and to avoid confusion. THanks

Not to be a smarty-britches or anything of the sort, but if the Sun were to be stretched top from bottom (would this be prolate?) into a comically obscene cylinder shape, would this cause any orbits to change or would it still act as the point of mass described above.

Thank you, E6S.