astro-

1.
a combining form with the meaning “pertaining to stars or celestial bodies, or to activities, as spaceflight, taking place outside the earth's atmosphere,” used in the formation of compound words:
astronautics; astrophotography.
Compare cosmo-.
Origin
< Greek, combining form of ástron a star, constellation, akin to astḗr star; cf. aster, -aster2
British Dictionary definitions for astro-

astro-

combining form
1.
indicating a heavenly body, star, or star-shaped structure: astrology, astrocyte
2.
indicating outer space: astronautics
Word Origin
from Greek, from astron star
Word Origin and History for astro-

element active in English word formation from mid-18c. and meaning "star or celestial body; outer space," from Greek astro-, stem and comb. form of astron "star," related to aster "star" (see star (n.)). In ancient Greek, aster typically was "a star" and astron mostly in plural, "the stars." In singular it mostly meant "Sirius" (the brightest star).

astro- in Science
astro-  
A prefix that means "star" (as in astrophysics), "celestial body" (as in astronomy), or "outer space" (as in astronaut).