You have to push it open.
Presumably he is still stuck in his castle in the far galaxy, and no longer has the Orb or the Golden Key to open the portal again. If you return to the asteroid, it is just a dead end.
After you beat all three planets (fire, ice, jungle) and have all three Space Knights with you, you can go to the secret planetoid at X-11 Y-64 in the asteroid belt. Pull the Golden Key from the crystal to open the portal.
It is at X-11 Y-84 in the Asteroid Belt. You can only go there after you have defeated all three of the planets (Jungle, Fire, and Ice) and have all three Space Knights with you, so that you can open the portal behind the Golden Key.
it is open ing June 10 or you can buy a ticket for 500 credits
There is no 4th space knight. You are the fourth knight, the Chosen One who will rescue the princess. When you have beaten the three planets, and have all three knights with you, go to the Giant Asteroid at X-11 Y-84 and you can pull the Golden Key to open the portal there.
you have to finish the puzzle then click on the door
Move the Mill to open the window
The knights will tell you of a secret asteroid hidden in the Asteroid Belt. Go there, and you will find it near X-11 Y-84. You will need all three knights to pull out the Golden Key and open the portal to the castle in a distant galaxy. You will fight the Binary Bard (Mordred) in his robot warrior suit. (see related question)
Once you defeat all three planets (jungle, fire, ice) and have all three knights with you, travel to the Giant Asteroid in the Asteroid Belt (X-11 Y-84) and use the Golden Key to open the portal to Mordred's hideout. (see related question)
Jump across the four Phoenix Eggs from the rope on the left. Key : jump when the egg is OPEN...by the time you land, it is closed.
you do the puzzle