This book and its sequel are AMAZING (Spoilers for the first page and a half or so): The plot point that kicks the whole thing off is when astronomers discover

This book and its sequel are AMAZING (Spoilers for the first page and a half or so): The plot point that kicks the whole thing off is when astronomers discover a star suddenly winking out of view. It turns out someone enclosed the star. But who? The inhabitants to hide / protect themselves? Someone else who wanted to trap the inhabitants? Everyone with any interest in sci fi should read these two books