Interstelar or Interstellar: How To spell?
The word Interstelar is misspelled against Interstellar, an adjective meaning "Between or among the stars; as, interstellar space."
Interstellar has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings interste & ar which should not be misspelled with single 'L'
Wrong Spelling:  interste-l-ar  Correct Spelling:  interste-ll-ar 
Explore spell check of Interstellar to spell without errors.