Question

How do gaseous planets form?

Answer 1

Hint: The properties of a planet is defined by its parameters with respect to the star that the planet is orbiting. One of the most defining parameters is the force of gravity on the planet by its star. This is clearly visible even in our solar system where we have the first four planets as terrestrial planets followed by four massive gas giants, that are, Jupiter, Saturn, Uranus and Neptune.

Complete answer:
To understand how a gaseous planet is formed, we first understand the fundamentals of how a planet is formed.
Planets are born out of clouds of gas and dust that orbit new stars. This dust swirled around the star in the shape of a flat disk, held in orbit by the star’s gravity. This disk is termed as Accretion disk. Each and every planet in the star’s orbit began as a microscopic grain of dust in the accretion disk. Overtime, the atoms in the disk combined and gained size to a point when they were sufficiently large enough to attract other particles by their own gravity. And after hundreds of millions of years, they became what we call today as planets.
Here, the Accretion disks that are near the star are turned into exo-planets as the strong wind from the star blows away the dust and leaves behind a rocky planet which comprises heavier elements as a result of the strong force of gravity experienced by the planet.
The Accretion disks that are farther away from the star do not experience strong wind or very strong force of attraction, hence the gaseous dust remains in the orbit of the disk. And due to weak gravitational pull, the planets cannot accumulate heavier elements. This results in the formation of gaseous planets.

Note:
Even in our solar system we can see that the gas giant “Jupiter” is almost 318 times bigger than the Earth but its weight is only 2.5 times that of Earth. This is mainly because Jupiter is $90\%$ Hydrogen and the rest is mainly composed of Helium and a small amount of other gases.