Star system: Solar System Click to see full answer. Correspondingly, is the Sun a star and why?As the only star we can observe in detail, it provides a basis for our understanding of all stars. The Sun is composed almost entirely of hydrogen and helium gas. Multimillion-degree temperatures in its dense core sustain nuclear fusion, providing the energy source for sunlight.Additionally, what type of star is the sun? G2V Secondly, is every star considered a sun? The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest). It is often said that the Sun is an “ordinary” star.Is the sun the biggest star?Answer: The largest known star (in terms of mass and brightness) is called the Pistol Star. It is believed to be 100 times as massive as our Sun, and 10,000,000 times as bright! In 1990, a star named the Pistol Star was known to lie at the center of the Pistol Nebula in the Milky Way Galaxy.