How do we know this comet, C 2023 a3, was last above earth 80,000 years ago?

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https://metro.co.uk/2024/09/29/see-a-once-80-000-years-comet-uk-october-2024-21699657/

I’ve seen a few posts and articles about this comet and how the last time it was this close to earth was about 80,000 years ago. I think that’s super cool but I don’t understand how we would know that.

In: Planetary Science

4 Answers

Anonymous 0 Comments

Comets like that don’t just roam around the universe at random – they are *orbiting the sun* just like everything else in our solar system. They simply have really, *really* big orbits. 

Orbits are predictable; calculating when an orbiting object will be here again (or when it was here last) is pretty straightforward math, relatively speaking. 

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