1. The Protoplanetary Disk:
* When a star forms, it is surrounded by a massive disk of gas and dust called a protoplanetary disk. This disk is the birthplace of planets.
* This disk is not uniform – it is denser and hotter closer to the star.
2. Condensation and Accretion:
* Terrestrial planets form in the inner, hotter region of the disk. Here, only materials with high melting points, like rock and metals, can condense out of the gas. These materials accumulate, forming planetesimals.
* Jovian planets form in the outer, colder region of the disk. Here, volatile ices, like water, ammonia, and methane, can condense alongside rocks and metals. These ices provide more material for the planetesimals to grow larger, eventually forming gas giants.
3. The "Snow Line":
* The boundary between the inner and outer regions is called the "snow line".
* Inside the snow line, it is too hot for ices to condense. This is why the inner planets are smaller and rockier.
* Outside the snow line, the ices condense, contributing to the formation of the larger, gas-rich Jovian planets.
4. Gravity and Gas Accretion:
* Once the Jovian planet cores are massive enough, their strong gravity attracts a large amount of gas from the surrounding disk.
* This gas accretion process creates the thick atmospheres of the Jovian planets.
In summary: The formation of terrestrial and Jovian planets is determined by the temperature and composition of the protoplanetary disk. The inner, hotter region allows for the formation of rocky planets, while the outer, colder region allows for the formation of gas giants.
