All about stars What are stars made of? They are enormous balls of hydrogen and helium, and they are extraordinarily hot. But not all stars are the same. If you look closely, some are quite red, like Betelgeuse, and others are blue, like Rigel. Blue stars are the hottest, red stars are a little bit cooler. Stars do not live for ever. New stars are made all the time, and old stars die, in the most amazing ways. In every galaxy, there are large clouds of gas, called nebulae. Inside these nebulae, new stars are born. There are small stars, middle-sized stars, and very large stars. Some of these large stars are a hundred times bigger than our Sun.