Not a doomsday that any of us will experience, but:
In about a million years, the orange dwarf star Gliese 710 is predicted to pass through the Oort Cloud, stirring up comets that may smash into the Earth and cause a mass extinction, just as a comet was probably what ended the dinosaurs.
I wonder how likely Gliese's plowing of the Oort Cloud is, to have catastrophic consequences - like, how unusual is it for another star to come this close to the Sun? How many times has such a close approach happened in the past?
When I have a question about astronomy I email Neil deGrasse Tyson and he always answers.
Thats nice Joan. I don't know how he has the time, but he can probably tell who is serious and has intelligent questions, like you, and answers them first.