This is the only Power Star in the Hurry-Scurry Galaxy. You need 18 stars to unlock the Hurry-Scurry Galaxy, which is located in the Fountain dome.
Firstly, you’ll need to make your way across the shrinking tiles towards the toads. When you step on one of the green squares it begins to disappear, so you can’t linger long. You can also take the time to grab the 1-up mushroom to the left of the toads.
When you’re ready, step on the green tile under the golden ? block to the left. Then when the tile has disappeared, jump down into the Launch Star - don’t forget to spin so Mario is launched!
Collect the Musical Notes
When you reach the new planet, you’ll notice that it is entirely made up of shrinking tiles. You need to collect all of the musical notes. It is fairly straightforward, just make sure you stay on one row of tiles, so you can use the other to go back if you need to.
When you have collected all the musical notes, the blackhole in the center of the planet will transform into a power star. You just need to drop down directly onto the Power Star to grab it.