Far as I'm concerned, they are stars--big, blobby red, yellow and blue stars. Trek was many things but it was never
remotely hard SF. Its take on biology (a human/Vulcan hybrid? with the radically different internal layouts, biochemistry and, presuambly, genetics? better a human/begonia hybrid, they'd be more closely related...) is as naive as its take on physics and that, imao, is part of its appeal.