Type-6 protostar
A type-6 protostar was a classification of protostar. 

In theory, the detonation of such a protostar could create a wormhole. In 2374, Ensign Harry Kim incorrectly guessed that Captain Kathryn Janeway planned to do so, with the subsequent wormhole enabling the  to travel back to the Alpha Quadrant. ()

Celestial objects
Astronomical classifications