For me I kinda have two laced together. Odd as they may be. Aliens and being abducted. I mean I know the odds of it happening to me out of the 7billion+ people on this planet is at odds, but it still has me with a slight fear of it. Mostly cause "what will they do with me" and "I'll never see home again" kind of thinking following it. I'm already pretty weak as it is. Don't have very much muscles. I mean I know there's a lot of good some aliens can do too, but the fear of those that do wrong doesn't help.

See LKWayvern's yeah black holes can be pretty terrifying too. I remember learning about those in school many years ago and fearing those too. Still kinda gives me goosebumps.