Why are there no gas planets inside the asteroid belt?

Answer 1

Planets form out of the material in the solar nebula (the cloud the Sun formed out of). This material consists of dust grains (rocky and metallic material), ice grains (mostly water ice, ammonia ice, methane ice), and gas (hydrogen and helium). Closer to the Sun (asteroid belt and closer) it was too hot for the ice grains to survive, so the interior planets (Mercury, Venus, Earth, Mars) formed out of just the dust grains. Farther from the Sun it was colder, so planets formed out of dust and ice grains.

Here's the important part - there's so much more ice than there is dust! So the outer planets were able to grow bigger. So big, in fact, that they were also able to hold on to all the gas that was out there, and grow to become gas giant planets. But the inner planets, formed only from the relatively small amounts of dust available, never got big enough to have enough gravity to hold on to that hydrogen and helium gas.

We've detected gas giant planets around other stars, and they are really, really close to their parent stars - some closer than Mercury is to our Sun! They were still formed far away, but for some reason they migrated inward. Astronomers are still trying to figure out all the specifics.

Ratna is not correct! Not at all correct.

Answer 2

It's an interesting question. Ratna is correct - HOWEVER, almost every exo-solar planet discovered has a massive planet bigger than Jupiter very close to the sun. One is 10 times closer to its sun than Mercury is to ours. Why is our solar system neatly laid out and over 100 others aren't?

There are a couple of theories. The prevailing is that all gas planets form in the outer reaches of the solar system, where gas can collect around a rocky core because the solar wind is not powerful enough to overcome the force of gravity. The gas planets then migrate for some reason from the outer reaches to the inner solar system, displacing all the inner rocky planets in the process.

But the details are still unknown.

Answer 3

It's a matter of temperature, really. As temperatures decrease, all particles, including the molecules of gases have less energy,i.e. they slow down. At the distances of the gas giants, the molecules of the light gases are slow-moving enough for the primordial planets to hold them gravitationally, which increased the planets' masses etc.
Originally the cloud from which the Solar System formed was of uniform constitution throughout, but the inner planets were in a zone of temperature which made Hydrogen retention impossible. Hydrogen being the primary constituent of the gas and dust cloud, this prevented the inner planets from becoming large gas giants.

Answer 4

About 5-billion years ago ALL the planets of our solar system were composed of gas. Those worlds closest in to the new sun were blown away by the sun's solar wind. Only those that had solid, mineral rich cores survived to eventually become Mercury, Venus, Earth, and Mars. Farther away from the sun, beyond Mars, only those gas planets that were massive enough survived the sun's solar wind and eventually became Jupiter, Saturn, Uranus, and Neptune.

Answer 5

current models suggest that the solar system was formed from a solar nebula, which is basically a giant spinning disk of gas and dust. since all the particles were revolving around the center of the disk, the force of the young sun's gravity caused the particles to undergo centripetal acceleration. since the rocky particles were heavier, they "fell" inwards (a greater force was needed to make them accelerate, and the force of the sun's gravity increased as you got closer to it). thus, all the rocky material was inside the asteroid belt, which formed the rocky planets, and all the lighter materials stayed outside the belt, forming the gas planets.

also, if a gas planet were placed closer to the sun, the solar wind would strip it of its gas layers.

Answer 6

there is a dwarf planet called ceres.