Hello Conner,

Our Sun probably began to form when a giant cloud of gas and dust in interstellar space began to contract under its own gravity, in a process that scientists call Kelvin-Helmholtz contraction. As the cloud or nebula collapsed, the gravitational potential energy of the material in the nebula was converted to heat energy. This caused the temperature in the center of the solar nebula to rise. Eventually, the center of the nebula became hot enough and dense enough for nuclear fusion to occur - and the Sun was born. The planets are thought to have formed from the leftover material in the nebula after the formation of the Sun.

One modern theory of how the gas giants like Jupiter formed says that the giant planets condensed directly from the gases of the early solar nebula just like the Sun did. In this theory, a slightly more dense part of the solar nebula near the present-day orbit of Jupiter began to contract under its own gravity. As this region contracted, it became more dense and more massive, allowing it to gravitationally attract more and more material until a giant, gaseous planet was formed. Jupiter actually releases more energy in the form of heat than it receives from the Sun, so it may still be contracting today. The fact that Jupiter emits more energy than it receives from the Sun supports the gravitational contraction theory. Also, Jupiter's Galilean Moons (Europa, Io, Ganymede and Callisto) appear to be like a solar system in miniature - which also suggests that Jupiter formed by gravitational contraction just like the Sun. However, Jupiter does not high enough temperatures inside its core for the nuclear fusion reactions that occur in the Sun. Jupiter also does not appear to be massive enough for fusion reactions to ever start in the future. So Jupiter will probably never become a star like our Sun.

Kris