Jupiter is the most important planet in our solar system in many ways. In universe binary stars are very common ,heavy gravity forces a nebula( cloud of interstellar gas and dust) to form a disk and the disk most of the time splits into two stars orbiting each other. Now the question is why Jupiter didn't convert into a star .Jupiter was in the process of becoming a star but ran out of material(gas) to convert into a star. Formation of binary stars depends on the availability of material and we are lucky that resulted in the formation of planets and our solar system. Astronomers call Jupiter as a failed star.
Jupiter with 70 odd moons resembles a mini solar system. Jupiter is more than twice as massive as all the other planets combined .Jupiter's structure resembles that of the sun, but would need to be 75 times its present mass to undergo the fusion of hydrogen that fuels a star.It is a gas giant composed of mostly of Hydrogen and Helium. Jupiter helps our planet in many ways, attracts or deflects many asteroids away from us because of its gravity thus protecting us from asteroids impact but once in a while could deflect an asteroid towards earth, very low probability.
Diameter of Sun and Jupiter compared to Earth
Earth 1.27 m x 107 1 x
Jupiter 1.43 m x 108 10 x (closer to 11)
Sun 1.39 m x 109 100 x (closer to 110)
