Hey me and a friend are here in the Stellarium and are stuck trying to find the key to open the other door to the key to defeat the alien dude. Can some one help? And tell where the lizards are?
Wow. Not enough info here... quest name? ... alien dude?
This link shows all of the quests in Celestia, and from your description, I think you might be working on one of these quests in the District of the Stars: "Teeth of the Shark" or "Into the Stellarium".
For "Teeth of the Shark", you need to go to Starkwaive's Lair.
This is pretty easy. Enter the area for "The District of the Stars".
You will see Thornton Lewis on your right.
Go down the ramp and turn right. Then go "up" the next ramp to the very top. You should see an "Inactive Protector" standing there.
Keep the "Inactive Protector" to your right side and walk past him.
You will see a "blue brick path" that leads down. Go just about 10 or 12 steps on that path, and Starkwave's Lair is on your right.
After you finish this quest and turn it in (to Thornton Lewis), then he gives you "Into the Stellarium".