 It has been a long @-@ held assumption that the majority of stars occur in gravitationally bound , multiple @-@ star systems . This is particularly true for very massive O and B class stars , where 80 % of the stars are believed to be part of multiple @-@ star systems . The proportion of single star systems increases with decreasing star mass , so that only 25 % of red dwarfs are known to have stellar companions . As 85 % of all stars are red dwarfs , most stars in the Milky Way are likely single from birth . 
