 Ceres ( / ˈsɪəriːz / ; minor @-@ planet designation : 1 Ceres ) is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter . Its diameter is approximately 945 kilometers ( 587 miles ) , making it the largest of the minor planets within the orbit of Neptune . The thirty @-@ third @-@ largest known body in the Solar System , it is the only one identified orbiting entirely within the orbit of Neptune that is a dwarf planet . Composed of rock and ice , Ceres is estimated to comprise approximately one third of the mass of the entire asteroid belt . Ceres is the only object in the asteroid belt known to be rounded by its own gravity . From Earth , the apparent magnitude of Ceres ranges from 6 @.@ 7 to 9 @.@ 3 , and hence even at its brightest , it is too dim to be seen with the naked eye , except under extremely dark skies . 
 Ceres ( / ˈsɪəriːz / ; minor @-@ planet designation : 1 Ceres ) <a href='drop_aux' title='1'><mark>is</mark></a>the largest object in the asteroid belt <a href='null_relcl' title='2'><mark>that</mark></a><a href='uninflect' title='3'><mark>lies</mark></a> between the orbits of Mars and Jupiter . Its diameter <a href='drop_aux' title='4'><mark>is</mark></a>approximately 945 kilometers ( 587 miles ) , making it the largest of the minor planets within the orbit of Neptune . The thirty @-@ third @-@ largest known body in the Solar System , it <a href='drop_aux' title='5'><mark>is</mark></a>the only one identified orbiting entirely within the orbit of Neptune <a href='null_relcl' title='6'><mark>that</mark></a><a href='drop_aux' title='7'><mark>is</mark></a>a dwarf planet . Composed of rock and ice , Ceres is estimated to comprise approximately one third of the mass of the entire asteroid belt . Ceres <a href='drop_aux' title='8'><mark>is</mark></a>the only object in the asteroid belt known to be rounded by its own gravity . From Earth , the apparent magnitude of Ceres <a href='uninflect' title='9'><mark>ranges</mark></a> from 6 @.@ 7 to 9 @.@ 3 , and hence even at its brightest , it <a href='drop_aux' title='10'><mark>is</mark></a>too dim to be seen with the naked eye , except under extremely dark skies . 
Ceres ( / ˈsɪəriːz / ; minor @-@ planet designation : 1 Ceres ) the largest object in the asteroid belt lie between da orbits of Mars and Jupiter . Its diameter approximately 945 kilometers ( 587 miles ) , wit it the largest of the minor planets within tdaorbit of Neptune . The thirty @-@ third @-@ largest known body in thdaolar System , it thedaly one identified orbiting entirely within the dait of Neptune a dwarf planet . Composed of rock and ice , Ceres is estimated to comprise approximately one third of the mass of the edare asteroid belt . Ceres the only object in the asteroid belt known to be rounded by its own gravity . From Earth , the apparent magnitude of Ceres range from 6 @.@ 7 to 9 @.@ 3 , and hence even at its brightest , it too dim to b seen with the naked eye , except under extremely dark skies .