Where is the portal in poptropica astro knights?

The portal to Binary Bard's lair is on a "giant asteroid" (it's a planetoid) in the Asteroid Belt, (down and to the left in space) specifically at X-11, Y-84. Before you go there, you have to beat all three of the planets (jungle, fire, and ice) and have all three knights with you (Sir Cador, Sir Peleas, and Sir Gawain). Otherwise, you cannot use the Golden Key.