It's pretty safe to say this new addition is kind of a troll by NASA on believers in astrology. That doesn't mean this is a FAKE prank. NASA doesn't believe in astrology, they just pointed out a correction.
For some people, it's a very confusing development! (Although some are still very secure in knowing their star sign)
via @dsweintraub_, @camerawhitt, @DanielleMNorman, @alishasaith, @PetitePasserine
And here's a list of the new signs, if you want to have your world rocked.