 The categorization of Ceres has changed more than once and has been the subject of some disagreement . Johann Elert Bode believed Ceres to be the " missing planet " he had proposed to exist between Mars and Jupiter , at a distance of 419 million km ( 2 @.@ 8 AU ) from the Sun . Ceres was assigned a planetary symbol , and remained listed as a planet in astronomy books and tables ( along with 2 Pallas , 3 Juno , and 4 Vesta ) for half a century . 
 The categorization of Ceres <a href='been_done' title='1'><mark>has</mark></a> changed more than once and <a href='uninflect' title='2'><mark>has</mark></a> been the subject of some disagreement . Johann Elert Bode believed Ceres to be the " missing planet " he <a href='been_done' title='3'><mark>had</mark></a> proposed to exist between Mars and Jupiter , at a distance of 419 million km ( 2 @.@ 8 AU ) from the Sun . Ceres was assigned a planetary symbol , and remained listed as a planet in astronomy books and tables ( along with 2 Pallas , 3 Juno , and 4 Vesta ) for half a century . 
The categorization of Ceres done changed more den once and have been da subject of some disagreement . Johann Elert Bode believed Ceres to be the " missin planet " he done proposed to exist between Mars and Jupiter , at a distance of 419 million km ( 2 @.@ 8 AU ) from the Sun . Ceres was assigned a planetary symbol , and remained listed as a planet in astronomy books and tables ( along w 2 Pallas , 3 Juno , and 4 Vesta ) fir half a century .