There are certainly lots of them. The good news is this: the universe is so unimaginably big, the probability of a really dangerous big scary object striking the Earth during our lifetimes is very low. The bad news is this: given enough time (and there certainly seems to be no shortage of that), at some point another big scary object will strike the Earth.
So what, you say? What can one person do to prevent such a thing? That's why you're seeing this item on this blog, actually. Genealogists are (generally) good recordkeepers. If you have a telescope (or a really outstanding pair of binoculars and the eyesight of a hawk), you can help NASA keep an eye on big scary objects in the sky: