Rocket, Rings of Saturn.
Radio telescope
Red dwarf star
Red giant star
Redshift (Doppler effect, etc.)
Retrograde (motion)
Regulus (star)
Rigel (star)
Radiant (of meteor showers)
Raagi
emue
The antonym for forward is backward, but the opposite direction can be reverse or rearward.
Raspberry
A bright and cheerful word starting with Y is yellow; a very important word starting with Y is you.
a space word for R could be Rhea the moon of saturn.
A six letter word for a bird of prey starting with the letter R is "raptor."
· Uranus
A word that starts with an R that describes you is responsible.
random
Ravishing like you
resect
recover
star
planet Pluto
· Hubble telescope
rotogravure