The SUN

WHAT IS THE SUN? The Sun is what is known as a main sequence star; that is, a sphere composed primarily of the two gases hydrogen and helium such that certain conditions are met. The first condition is that it must have a mass falling within a certain range. Though debated, this range is generally accepted to be between approximately 1.4 x 10 29 kg and 3.0 x 10 32 kg. (This range is often describe as at least 75 times the mass of Jupiter and no more than 150 times the mass of the Sun itself.) The second and most important condition is that nuclear fusion must be present. Nuclear fusion is the process whereby two lighter atomic nuclei join or “fuse” together to produce a heavier atomic nucleus. In the context of stars, hydrogen is the lighter and helium the heavier. SIZE OF THE SUN The size of the Sun compared to the largest known stars ( red giants ) is not very big. However, if compared to the most common type of star in the universe, the red dwarf, the Sun is q...