The Keyhole Nebula Near Eta Carinae . ... Credit Copyright: Anglo-Australian Telescope Board Explanation: The dark dusty Keyhole Nebula gets its name from its unusual shape. Designated NGC 3324, the Keyhole Nebula is a smaller region superposed on the bright Eta Carina Nebula . The Eta Carina Nebula is the largest nebula in angular extent on the sky, larger than the famous Orion Nebula , but its southerly location makes it less familiar to Northern Hemisphere skywatchers. ...