Question

DQ: Why are the Jovian planets significantly bigger than the Terrestrial planets? Why do they have more moons?

Answer 1

These planets have larger sizes and masses.

Terrestrial planets :- include Mercury, Venus, Earth, and Mars. These planets are relatively small in size and in mass. A terrestrial planet has a solid rocky surface, with metals deep in its interior. In the solar system, these planets are closer to the sun and are therefore warmer than the planets located farther out in the solar system.

Jovian planets:- include Jupiter, Saturn, Uranus, and Neptune.  These planets have larger sizes and masses. Jovian planets do not have solid surfaces. They are sometimes called gas giants because they are large and made mostly of gases. Small amounts of rocky materials are only found deep in the cores of Jovian planets. In the solar system, Jovian planets are located farther from the sun than terrestrial planets, and are therefore cooler. Scientists have found more than 100 Jovian planets around other stars.

Jovian planets significantly bigger than the Terrestrial planets because ..

• the light pressure and solar wind from the star will tend to strip any atmosphere from the forming planets and asteroids, unless they are massive enough to retain it by gravity. In particular lighter elements like hydrogen and helium will only be retained in significant proportion in planets over a certain mass. Once planets have such a mass they will grow considerably, collecting gases from the surrounding disk, while their smaller cousins will tend to stay smaller. so because of ths reason terrestrial planets are smaller than jovian.
• A large part of this has to do with the sun. ‘rocky’ planets have all of their volatile elements ‘boiled off’ by the heat of the sun (Hydrogen, Lithium, Helium). The Jovian planets DO NOT receive enough solar radiation for this to happen so the lighter elements remain and accumulate over time.