Stars are massive shining spheres of hot gas, the closest of which is our Sun. Stars are primarily made of hydrogen, smaller amounts of helium, and trace amounts of other elements. Even the most abundant of the other elements present in stars (oxygen, carbon, neon, and nitrogen) are only present in very small quantities. Those stars which you see with your naked eye in the night sky all belong to the Milky Way Galaxy, the huge system of stars that contains our solar system.