Not much, it turns out. The most common sea star in the North Atlantic (and the waters around Star Island) derives its name from being just that: the common sea star. Otherwise known as Asterias rubens for you scientists. You’ve likely seen them many times in the marine lab over the years.
So what, then, about the other ubiquitous species the Northern sea star or Asterias vulgaris? Turns out scientists have long ago concluded they are the same species. This two-named sea star eats bivalves (a favorite prey item is the blue mussel) and gastropods. They also eat crustaceans and worms. They act both as active predators and scavengers.
P.S. We stopped calling them star fish a long time ago since they actually aren’t much like fish. They do not have gills, scales, or fins like fish do and they move quite differently from fish. While fish propel themselves with their tails, sea stars have tiny tube feet to help them move along.
Another common species in the North Atlantic, around Star, is the Forbes seastar or Asterias forbesi.