Here's the list arranged from smallest to largest:
- planet
- stars
- galaxy
- nebulae
(Note: In the typical hierarchy, stars can be both larger than and sometimes classified with galaxies depending on context, but generally, in terms of scale, planets are the smallest, followed by individual stars, then galaxies, and nebulae can vary in size but are often considered large collections of gas and dust that can form stars and solar systems, making them comparable to galaxies depending on the specific nebula.)