Closing the browser window will put you back on Arturus when you reboot, or you can fly back to Poptropica planet (X-56 Y-52) and land there. In either case, the spaceship you had will be parked on the top of the castle.
(see related question)
You do not get or use a bucket on Astro Knights Island.
There is no treasure chest on Astro Knights Island.
There are no bird eggs in astro knights island.
its on the island
How do you talk to the girl in the hay loft at astro knights island?
On every island you have to be the one to save whatever needs saving. That includes the kingdom in Astro Knights Island.
Once you have built a new spaceship on Astro Knights Island, it will park on top of the castle whenever you leave the island.
on astro knights island
With Mordred
it is in the left
Astro Knights
It is on tp of the castle roof in astro knight island