<Tr> <Th> Magnesium </Th> <Td> 0.05% </Td> </Tr> <Tr> <Th> Sulfur </Th> <Td> 0.04% </Td> </Tr> <P> The Sun is the star at the center of the Solar System . It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process . It is by far the most important source of energy for life on Earth . Its diameter is about 1.39 million kilometers, i.e. 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System . About three quarters of the Sun's mass consists of hydrogen (~ 73%); the rest is mostly helium (~ 25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron . </P> <P> The Sun is a G - type main - sequence star (G2V) based on its spectral class . As such, it is informally referred to as a yellow dwarf . It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud . Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System . The central mass became so hot and dense that it eventually initiated nuclear fusion in its core . It is thought that almost all stars form by this process . </P>

What percentage of the solar system is the sun