A star is a huge ball made of hot gases. The main gas in a star Is hydrogen. Thy hydrogen atoms are constantly bumping into each other with so much force that it makes the hydrogen burn. This reaction produces lots of heat and light, which makes the stat shine. When hydrogen atoms collide with each other give out this light, another gas called helium is also produced in the process. So, a star is basically made up of two main gases hydrogen and helium.