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To be slightly pedantic: our sun is a star in the galaxy, so as the entire galaxy rotates we would not pass in and out of a galactic arm. We would rotate with i
by _ah 5y ago
To be slightly pedantic: our sun is a star in the galaxy, so as the entire galaxy rotates we would not pass in and out of a galactic arm. We would rotate with it.
- lasc4r 5y agoMaybe not. https://en.wikipedia.org/wiki/Density_wave_theory https://en.wikipedia.org/wiki/Density_wave_theory
- wlesieutre 5y agoThe galaxy isn't a rigid spinning object though, it's composed of many stars acting under gravitational influences. Like our solar system, objects closer in will orbit faster than objects further out. Rather than fixed structures, the arms are more like a standing wave of greater density. Some related links https://en.wikipedia.org/wiki/Density_wave_theory https://en.wikipedia.org/wiki/Density_wave_theory https://en.wikipedia.org/wiki/Galaxy_rotation_curve https://en.wikipedia.org/wiki/Galaxy_rotation_curve https://www.nature.com/articles/s41550-018-0627-5 https://www.nature.com/articles/s41550-018-0627-5
- mjw1007 5y agoAs I understand it, galaxies don't rotate like rigid bodies: stars further from the centre take longer to go round than ones closer in, much like planets further from the sun take longer to complete an orbit. If stars that start off inside an arm remain so, but the outer part of the arm goes round more slowly, the arm would get wound 'tighter' as time goes on, and this doesn't seem to happen. I think what's really going on isn't yet well understood, but it's likely to be that the arms are something more like a standing pattern, and stars do indeed move in and out of the arms as time goes on (something like the way a traffic jam can move more slowly than the individual cars that it's made of).
- _ah 5y agoFair point. So maybe we should say that our sun would occasionally be a part of the galactic arm as the pattern morphs and re-forms. A fun concept.
- ananonymoususer 5y agoIt turns out that the stars further from the center don't take as long as one might think. Observations of this phenomenon led to the development of the theory of dark matter. https://en.wikipedia.org/wiki/Galaxy_rotation_curve https://en.wikipedia.org/wiki/Galaxy_rotation_curve
- deleted 5y ago[deleted]
- jazzyjackson 5y agoNot pedantic at all, I for one have never speculated about galactic dynamics So in the solar system the inner planets have faster orbits than the outer planets, I assume it would be the same on a galactic level - if we’re a slow poke out on the edge, could there be some region of the galaxy that orbits the core 8x faster than us such that we’re periodically effected by it? Edit LOL my sibling comments have filled in some info for me on the mean time
- egberts1 5y agoMost stars would not pass in and out of each spiral arm of a galaxy. Perhaps it’s just our Sun that does it.