"Planetarium" Natural Recordings by Native Speakers
A building or a dome-shaped structure where a show of the night sky, particularly the stars, planets, and celestial objects, is projected onto the interior surface for educational and entertainment purposes.
There is no word "planer". However, I'm assuming you meant "planner" or "plane(r)". Planner: a person who plans or arranges things in detail. Planer: Not a commonly used word in modern English, but it could be a rare or obsolete Term, or possibly a proper noun. Plane(r): a flat surface or a machine that flies through the air, or a musical instrument played with a keyboard.