Ceres

Ceres was an dwarf planet because, he is now asteroid. See what happens when Ceres hits earth Actually it was diameter 946 kilometers, more other asteroids could exist.

It could actually happen with an event if the Ceres in on their way, if you couldn't see exist. But why would we know? Why would we know that we can see the Asteroid? And why could anyone die after hitting any asteroids?

Well the answer is to watch this video.