Celestial bodies in Mario’s Earth’s atmosphere?

Hello, guys; I have a question whose answer could help everybody understand the Mario series's cosmology a little better.

In Super Mario Galaxy 2…
World 1 seems to be between the planet's troposphere and stratosphere, yet two celestial bodies (not "planets" of "galaxies") can be seen in the former from the latter.
https://youtu.be/qcVGKh7cUDc?t=1974
And the title screen shows more celestial bodies in what seems to be also the troposphere.
https://www.youtube.com/watch?v=wX8CBZKdWwE

What's the explanation for those appearances, please?
 
I think it's because when Mario boards Starship Mario the surrounding atmosphere is the one seen in World 1 because the Starship started there in world 1. The title screen might just be the same area so that there won't be any spoilers, but this is just my guess.
 
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