The five three-letter words below have something in common that has nothing to do with their meanings. Can you determine what it is?

AND
CAN
CAP
GEM
SAG

HINT: The clue words are the first three letters of five related words.

Answer:

The clue words are the first three letters of a galaxy and four star constellations:

ANDROMEDA
CANCER
CAPRICORN
GEMINI
SAGITTARIUS