<prompt> Translate the following text to EnglishHata hivyo, mfumo wetu wa jua ndio mfumo pekee tunaojua kwa undani, na imekuwa jambo la busara kwetu kudhani kwamba hizo zilikuwa ni makundi mawili tu ya sayari.  <response>: Ours is the only solar system we know in detail, however, and it has been reasonable for us to assume that these were the _only_ two planetary classes. 