Yes, the digestive juices of a sea star can digest human tissue as well because they contain enzymes, which are proteins that capable of chopping up other biomolecules. Since all organisms are made up of the same building blocks, such as proteins, sugars and fats, tissues made up of these building blocks can be destroyed by the same chemical processes.

The answer to your question is "perhaps". Although there are exceptions, sea stars (asteroids) typically feed on sessile (or attached) invertebrate prey. Because they have limited mobility, they cannot effectively feed on rapidly moving species and rely on long periods of time for their digestive enzymes to take effect. There are, however, exceptions to this. In the North Pacific, asteroid Stylasterias, the pedicellaria (the small claw-like protrusions on the aboral surface that predominantly function as an anti-fouling mechanism) are so well developed that they can easily immobilize a small fish that ventures too close.

But now, back to your original question. While the digestive enzymes secreted by asteroids are probably capable of digesting human flesh, I can't off hand think of any volunteers that would be willing to investigate the duration of exposure required to do so. There have, however, been several reported cases of asteroids "swarming" to animal carcasses on the sea floor, everting their stomachs, and rapidly (keep in mind that everything in asteroid time is slow) skeletonizing the victim; quite an eerie sight when viewed with time-lapse photography .