The Solar Year has huge effects on our climate, and the signs of passing seasons are physically evident on Earth. I recently learned about the Galactic Year. To my understanding, our sun orbits the Milky Way galactic center about every 200-225 million years. Do we know if there are any "seasonal" changes due to our position in the galaxy? One season of the orbital period (50+ million years) feels like a long enough time to leave a mark, if any effect exists:

  • in the formation of solar system objects?
  • the bombardment of planets and moons with meteors?
  • the number, type, distribution, or trajectory of comets?
  • the shape or density of the Oort Cloud?
  • in Earth's geologic record?
  • (at a stretch) mass extinction events?

Obviously you can just say "gravity affects everything, of course the solar system is influenced to some degree by other objects." But I mean specifically, is there evidence for any cyclical pattern which might be related to our position in the galaxy?

  • $\begingroup$ I've read similar things that drew correlations between the "Galactic Year" and major extinction events on Earth. One such article, Sun's galactic journey linked to mass extinctions, comes to mind. It was an interesting idea from a web site I'd never heard of, nor have I heard is authoritative in any way, shape or form. $\endgroup$ – Greg Burghardt Jul 23 '20 at 20:41
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    $\begingroup$ The Sun causes seasons on planets that either are tilted on their axis or have a very elliptical orbit (or both, like in case of Mars). At the center of the Milky Way there's a supermassive black hole whose heat has little effect on this planetary system since our system is in the outer rim of the Milky Way galaxy, far away from the galactic core. I don't think there are any specific orbital occurences except for what you write in quotes. $\endgroup$ – Ioannes Jul 24 '20 at 8:10

Mass extinctions have been linked with the Solar System's oscillations up and down through the galactic plane (the Galactic Cycle). You could also take a look at this question.


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