Jupiter, despite being the largest planet in our solar system, is not considered a star or a brown dwarf. Here are the key characteristics that distinguish Jupiter from other large celestial bodies:
Composition: Jupiter is primarily composed of hydrogen and helium, similar to the composition of stars. However, its mass is not sufficient to sustain nuclear fusion, which is the process that powers stars. Brown dwarfs, on the other hand, have a mass range between that of the heaviest gas giants (like Jupiter) and the lightest stars. Brown dwarfs can undergo limited nuclear fusion of deuterium and lithium, but they lack the sustained fusion reactions found in stars.
Energy Generation: Stars, including brown dwarfs, produce energy through the process of nuclear fusion. The fusion of hydrogen atoms in stars releases enormous amounts of energy in the form of light and heat. Jupiter, as a gas giant, derives its energy primarily from the residual heat left over from its formation and gravitational contraction. It does not possess an internal fusion process like stars or brown dwarfs.
Luminosity: Luminosity refers to the amount of light and energy a celestial body emits. Stars and brown dwarfs have a relatively high luminosity, which is a result of ongoing nuclear fusion reactions. Jupiter, however, reflects light from the Sun but does not generate significant internal heat or emit substantial amounts of energy. Its luminosity is much lower compared to stars or brown dwarfs.
Stellar Evolution: Stars and brown dwarfs evolve over time, undergoing various stages from formation to eventual demise. They can exist for millions or even billions of years, depending on their initial mass. Jupiter, as a planet, does not undergo the same evolutionary process as stars or brown dwarfs. It formed alongside other planets during the early stages of the solar system's formation and will continue to exist as a gas giant.
In summary, Jupiter's composition, lack of sustained nuclear fusion, lower luminosity, and different evolutionary trajectory differentiate it from both stars and brown dwarfs. While it shares some similarities with these celestial bodies, Jupiter remains distinct as a gas giant planet within our solar system.