system
Given the following post, respond as if you're commenting on Reddit:
human
If stars use up their hydrogen before exploding and then a new system forms (like ours) where does the hydrogen in that system come from?
gpt
Stars don't use up *all* their hydrogen, just the hydrogen in the core. There's plenty of hydrogen elsewhere in the star which doesn't get fused into helium. When a star sloughs off its outer layers at the end of its life, the discarded hydrogen can form (part of?) a new star and be used for fusion.