The Sun is about 4.5 billion years old. Our Sun is made up largely of hydrogen and helium gas, and is one of more than 100 billion stars in our galaxy. The Sun is the largest object in our solar systemm, and contains about 98% of the solar system's total mass (the planets and their moons account for less than 2% of the solar system mass). The Sun rotates around its axis with one rotation taking about 27 days.
The Sun's energy comes from nuclear fusion occuring deep inside its core. This is the same process that is used in hydrogen bombs. Energy generated by fusion processes in the Sun's core takes about a million years to reach its surface where it becomes visible; there is enough solar fuel to go for another five billion years.
