This is part 24 of my 100% Super Mario 3D World Walkthrough.
This part includes World Star-2 Super Galaxy.
Completing this stage unlocks Rosalina as a playable character.
Below are the times for the green stars and stamp in this stage.

01:08 - Green Star #1
02:01 - Super Galaxy Stamp Location
02:29 - Green Star #2
02:55 - Green Star #3