You could do this with seven stars and arrange them like the Matariki cluster
For Baby Geeks: The Best Nerdy Mobiles. That would be awesome for my kid if I had one.
Star Mobile- Blue Nursery Mobile, Shower Gift, Photographer Prop on Luulla or make out if snowflakes
Items similar to Rainbow Origami Star Mobile on Etsy
The Hudson Mobile - Modern Space Age/Robot Nursery Mobile in Blue and Red
Hoop, Ribbon, CardStock Shapes, Beads, and Beading String
Party Things curated by Best Birthdays on Etsy
Yarn ball ceiling decorations for the craft room, plus super cute girl and boy room ideas - this actually made me think of how cool it'd be to have a hanging solar system in a kids' room!
Moon and stars mobile