A nebula formed around a neutron star, explored by the Enterprise-D in 2368, where an energy being took the shape of a child's imaginary friend.
FGC-47 is a nebula featured in the Next Generation episode Imaginary Friend.
While the Enterprise-D studies the nebula, a point of light enters the ship and reads the mind of Clara Sutter, a lonely girl aboard. It appears to her as Isabella, the invisible playmate she has invented, now visible and far less kind.
At the same time strands of energy within the nebula begin dragging on the ship and draining its shields. Isabella turns out to be a scout for the beings that live there, who feed on such energy and are judging whether the crew deserve to survive. Picard persuades her that the rules she resented exist to protect children, and the ship is allowed to leave.