Stars are formed from clouds of gas and dust in space. These clouds are called molecular clouds or nebulae. Gravity causes these clouds to collapse under their own weight, and as they do, they heat up and start to glow. This is how stars are born.

The life cycle of a star is determined by its mass. The more massive a star is, the shorter its life span will be. A star spends most of its life burning hydrogen gas in its core and releasing energy in the form of light and heat. This process is called nuclear fusion. The energy released by nuclear fusion helps to balance the inward pull of gravity.

When a star runs out of hydrogen fuel, it will begin to cool down and collapse in on itself. If the star has a mass less than about 8 times that of the sun, it will become a white dwarf - a tiny, hot ball of gas that glows for billions of years. If the star is more massive, it will explode in a supernova and then either collapse into a neutron star or a black hole.

The life cycle of stars is essential for creating the elements necessary for life. The death of a massive star in a supernova explosion can create heavy elements such as gold, silver, uranium, and plutonium. These elements are then spread throughout space, where they become part of the material that new stars, planets, and eventually life is formed from.