> [a] This also implies that they can not be converted into time machines
This doesn't seem like "classical" wormhole, right?
What would happen is more complicated to answer if the wormhole stays open. The star would effectively have double the surface area, but apart from that, the consequences for the star's future development elude me right now.
Wouldn’t it cause the core to collapse inwards though, as it would basically provide a “safety valve”-type release (though I presume if you were to place it on the edge of the fusing core, it would basically replace a patch of pre-existing surface area at the expense of convection and radiation pressure above taking a nose-dive).