If humanity ever got to the point of being able to explore new planets (assuming we could land there), are there any known entities in the universe that are so massive that gravitational time dilation could really become a serious issue? In other words, if the explorers landed on the planet/entity, could it create a potential disaster as their time would slow down so much that the cooresponding operations on earth would have long since expired?
From what I read, most gravitational time dilation effects are minimal, nanoseconds. When/where does it become a real problem? Short of black holes, because of the obvious obstacles surrounding them.