Question

Explain the theory which accounts for why there are two very different types of planets in our solar system?

Answer 1

# There are two types of planets in our solar system.

1. Terrestrial planets (Earth like): Mercury, Venus, Earth, and Mars

They are small and rocky in nature.

2. Jovian planets - Jupiter, Saturn, Uranus and Neptune

They are made of  tiny chunks of ice and bits of rock.

# At the very first step Sun was formed and due ot its gravitation force and heat only, other planets were formed.

# Creation of Sun in brief:

Sun and planets are born from the clouds of gas and dust. Around five billion years ago, a giant cloud floated our Milky Way galaxy. This cloud, called a nebula, was made up of dust and gas, mostly hydrogen and helium, with a small percentage of heavier atoms. These heavier atoms had been formed earlier in the history of the Universe when other stars aged and died.

This cloud/nebula began to contract, collapsing in on itself. The atoms, once separated, began to jostle each other, generating heat. In the rising heat, the atoms collided more frequently and more violently. Eventually, they reached a temperature at which the protons at the centers of the atoms began to fuse, in a process called nuclear fusion. As they did, a tiny bit of matter transformed into a whole lot of energy, and a star was born and this start is Sun.

# Creation of planets

After the formation of Sun only, other 8 planets of our solar system was formed.

The material in the nebula not absorbed into the Sun swirled around it into a flat disk of dust and gas, held in orbit by the Sun’s gravity. This disk is called an accretion disk. The accretion process - planetesimals colliding to form planets - heated up the planet (think of rocks and ice blocks crashing into the planet - heat is generated in the collision). As the solid materials were heated up they became liquid - the denser liquids fell to the center of the planet. This differentiation (core formation) further heated the planet. This heating happened to all planets - but the bigger the planet the more heat that was generated. Slowly the planet begins to lose heat - by conduction, convection, eruption and radiation - the smaller the planet, the quicker it lost heat. On the smaller, terrestrial planets a crust of solid rock formed on the surface. The largest planets - the gas giants - still retain much of their primordial heat of formation.

So in sort,  the condensation of refractory materials leads to the creation of rocky & metallic terrestrial planets. On the other hand, In the solar nebula the temperature dropped below 0° C (273 K) somewhere between 3 and 4 AU - this distance is sometimes called the "snowline" - beyond which water condensed and clumped into snowballs, eventually coalescing into many planetesimals. With the large volumes of the outer solar system occupied by snowballs, these accumulated into LARGE planets - large enough to hold in hydrogen. Since hydrogen is so abundance, these became GIANT planets. This leads to creation of Jovian planets.