 Stars are not spread uniformly across the universe , but are normally grouped into galaxies along with interstellar gas and dust . A typical galaxy contains hundreds of billions of stars , and there are more than 100 billion ( <unk> ) galaxies in the observable universe . In 2010 , one estimate of the number of stars in the observable universe was 300 <unk> ( 3 × 1023 ) . While it is often believed that stars only exist within galaxies , <unk> stars have been discovered . 
