Life Cycle of a Star. Stars are formed in clouds of gas and dust, known as nebulae. Nuclear reactions at the centre (or core) of stars provides enough energy to make them shine brightly for many years.
A star is born once it becomes hot enough for fusion reactions to take place at its core. Stars spend most of their lives as main sequence stars fusing hydrogen to helium in their centres. The Sun is halfway through its life as a main sequence star and will swell up to form a red giant star in around 4.5 billion years. hope this helped :)
