why are asteroids not considered planets?

Question

y scientifically are they not planets?

Answer 1

The easy answer: they don't fit the definition as set out by the International Astronomical Union.
http://en.wikipedia.org/wiki/Planet

However, they are called "minor planets" so, in a way, they are planets, just minor ones. Like Pluto is still a planet, but only a dwarf one.

Most of them are so small that their own gravity is too feeble to have shaped them in a sphere. They are basically large pieces of rock.

When the first ones were discovered (1801 and onwards), they were called planets. Then, when it became apparent that there was a whole buch of them, astronomer reconsidered and decided to create a special class called minor planets.

They are also called asteroids because they had the appearance of a star in a telescope. 'Real' planets showed up as disks. You could actually measure their apaprent diameter and, maybe, see features on them. Asteroids always looked like points of light, without size and without features.

Answer 2

Asteroids actually used to be considered minor planets. When the first asteroid was discovered in the asteroid belt, it was assumed that it was in fact a planet predicted by the (now obsolete) Titius-Bode Rule. Later, after more were discovered, asteroids were considered to be fragments of a destroyed planet, which would have had an orbit of where the asteroid belt is now. The confusion was mainly because asteroids followed Kepler's laws of planetary motion, which is what was initially used to define planets.

However, in modern scientific terms, an asteroid is thought to be a remainder of of the planetary building blocks, or planetisimals. But some larger asteroids, such as Ceres, have now been classified as dwarf planets, along with Pluto.

Answer 3

The main reason is their mass, it's just too small for a such a body to be considered a planet. On top of that, asteroids look like big rocks in space more like fragments or debris after a collision. That's also the reason why Ceres (a big asteroid) is now called a dwarf planet and not an asteroid any more. It's because of its bigger mass (which also lead to its round shape we see in the photos etc.)

Answer 4

Because they are too small. There has to be a lower limit to how small an object in space is to qualify as a planet otherwise every speck of dust orbiting the Sun would be a planet. So how small? 5,000 miles? 1,000 miles? 500 miles? 10 miles? 1 mile? 100 feet? At some point, EVERYBODY would agree it isn't a planet. The largest asteroid, Ceres, was recently reclassified as a dwarf planet, along with Pluto and Eris. Ceres is about 600 miles wide.

Answer 5

"Planet" and "asteroid" are just words people use to help understand star systems. There is no big conceptual difference. It's a lot easier to talk about the 8 planets without naming each and every one.

However, there are definite differences. A planet (within our solar system):

1. is in orbit around the Sun;
2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (near spherical) shape; and
3. has cleared the neighbourhood around its orbit.

"Asteroids" have never been rigorously defined. However, most definitions of them fit within the category of "small solar-system bodies," or SSSBs. Read the source article for stuff about those.

Answer 6

The separating point between planets and non-planets is largely arbitrary. Ceres for example is nearly 1000 km across, and spherical, and also orbits the sun, yet it is not a planet.

I think we should call any spherical mass larger than 500 km a planet, that way there would probably be thousands of planets in our solar system, which is more fun for me to think about than countless 'planetoids'.

When we fully explore the furthest reaches of our solar system, we will probably discover many new planets, some of which will probably end up being larger than the Earth.

Answer 7

because of the fact the asteroid belt does not meet the definition of planet. There are 3 issues an merchandise would desire to require to be called a planet, that are: one million -- Is in orbit around the solar 2 -- should be very very nearly sphere 3 -- Has "cleared the neighbourhood" around its orbit desirable, the asteroid belt is in orbit around the solar, besides the shown fact that the asteroid belt isn't sphere - this is purely a team of asteroids in orbit around the solar. additionally, I see you reported "planets" and not "planet", nicely that is violating rule kind 3 - because of the fact each and each asteroid does not have "cleared the neighbourhood" around its orbit. this is believed the asteroid belt tried to variety right into a planet, however the gravity from Jupiter could rip it aside every time it tries to variety right into a planet.

Answer 8

because they are too small compare to planets ;instead they are called minor planets

Answer 9

They are just pieces of a planet or ice

Answer 10

I guess becouse they travel without a trace or dont have an orbit