This is one of the most fun science crafts to make. It may be a lot easier than you might expect it to be. All you need is Styrofoam balls of different sizes
Student Project: Make a Scale Solar System
Build a Solar System Model
Solar System Scale Model
Craft / Making A Solar System – Clara and Macy
Created Solar System Model with Paper and Balls : r/crafts
Make Your Own SOLAR SYSTEM STEM Homework Model Kit Set 14 Poly Balls & Rods
Solar System Model in a Jar - Teach Beside Me
Nabanita, kid's activities
24 Piece DIY Solar System Model Kit with 14 White Foam Balls and 10 Bamboo Sticks for Science Projects