Why are stars and planets exactly round?

Answer 1

Well actually they are not perfectly round. They actually becom spherical, bulging at their equators due to centrifugal force of their rotation.

The general round shape is due to the attempt to equalize the effects of gravity created by the mass itself. Gravity attempts to pull all mass toward the center of the mass. All things being equal, the shape results in a ball.

There you have it! Have fun!

Answer 2

Yes, Planets seem to be spheres, not cubes or cylinders or oddball rocky shapes. Some smaller bodies such as asteroids or Mars moons Phobos and Deimos, do have odd shapes, but larger bodies like the nine planets and most of their moons do look like spheres. That's because of the nature of gravity. You can think of gravity as a force that points inward toward the center of the planet so that every part of the surface is pulled evenly toward the center, resulting in a spherical shape.
Of course, planets are not perfect spheres because mountains and valleys and even skyscrapers are all deviations from the spherical shape. However, as planets get larger, gravity gets stronger, until eventually large objects on the surface are crushed under their own weight. That's why we don't have mountains that are 50 miles high or skyscrapers that are 2,000 stories tall. Planets stay basically spherical because any large deviations get crushed.

Although gravity keeps planets close to spherical, there are other forces that cause deviations from the basic spherical shape. For example, the rotation of the earth once every 24 hours, causes an apparent centrifugal force which creates a bulge at the equator. In fact the earth's diameter at the equator is 7,926 miles while the diameter between the poles is only 7,900.

Answer 3

The roundness comes from the fact that gravity pulls everything toward the center. Stars and gaseous planets have no solid material to resist the pull of gravity. However, certain processes will create temporary structures like clouds and solar flares that shoot outward. Also, as a previous poster said, if the stars and planets are spinning fast enough, they will bulge outward at their equator.

Solid planets will form mountains that stand up in spite of gravity. What stops the mountains from getting really large? Erosion keeps breaking the mountains down. Water and air does this on earth, and on other planets without atmospheres or water, it is meteorites that keep the mountains from getting really large. Also, mountains are only strong enough to reach a certain height before they crack and fall apart.

The strength of gravity varies with the size of the object in space. As the bodies get smaller, their gravity decreases and so the mountains can grow larger. Asteroids and small moons can have very irregular shapes. The link below shows the shape of the asteroid Castalia, which looks kind of like a bean. Phobos (see link below) is about 30 miles wide and it has an enormous crater in the side. Its overall shape is not very round either.

Answer 4

All this talk of oblate spheroids aside, the earth is more perfectly spherical than any billiard ball. Even when you account for surface features like mountains.

Why are planets (and stars) round? For the same reason why rocks fall downhill: gravity pulls down the high spots and fills in the low spots. When all particles seek to get as close to the center of gravity as possible, the result is a sphere. Okay, call it an oblate spheroid if you must account for the effects of the spinning and what-not, but for pretty much any practical purposes, it's a sphere.

Answer 5

ya..they are not exactly round,but the reason why the stars and planets have this same shape is the existance of gravity

Answer 6

Stars and planets are not exactly round and our earth isn't either.

Answer 7

Not sure they are all exactly round but you should see the one I just made with Bryce software lol...it looks exactly round lol

Answer 8

They're not! Gosh! Don't assume such things. The Earth is an oblate spheroid due to its rotation, specifically centrifugal force.

Answer 9

spinning and gravity hold s them together causes it to be round. All are not round.

Answer 10

They aren't. Some are more oval or shaped alittle different then round.