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James Webb Space Telescope reveals that most galaxies rotate clockwise

(www.smithsonianmag.com)
352 points instagraham | 1 comments | 31 Mar 25 10:31 UTC | HN request time: 0.213s | source
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vincnetas ◴[31 Mar 25 12:10 UTC] No.43534038[source]▶
But rotation direction depends on the observer. If i see galaxy spinning clockwise, this means someone observing galaxy from behind it sees it rotating counter clockwise. So are we just located so in the universe that we see 2/3 spinning clockwise and another counter?
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rob74 ◴[31 Mar 25 13:13 UTC] No.43534679[source]▶
It just occured to me that "rotation direction" is a pretty coarse measurement. Actually, you could look at the angle of a galaxy relative to ours, where (let's say) 0° is viewed exactly from "above" (rotating clockwise), 180° is viewed exactly from "below" (rotating counterclockwise), 90°/270° is viewed side-on etc. How about some stats based on this parameter?
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smeej ◴[31 Mar 25 21:43 UTC] No.43540307[source]▶
What does "above" or "below" even mean in the context of something without a top or bottom? Or are you defining "above" to mean "the vantage point from which the galaxy appears to be rotating in the direction of earth clocks" for the purpose of this question?
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1. bbor ◴[01 Apr 25 02:30 UTC] No.43542236[source]▶
Not to disagree with your justified Socratic questioning, but this sparked my interest and I figured I'd share my (novice!) TIL: it appears the IAU uses a coordinate system based on our solar system on January 1st 2000, 00:00 AM, or "J2000.0". Thus (0, 0, 0) is at the ~center of Sol and the x and y are within Earth's orbital plane, which means the z axis is orthogonal to that. In other words, it seems like "above"/"up" in a astronomical sense denotes the same approximate direction as "Northward"/"North", which is pretty fascinating!

Of course as an arrogant computer scientist I think they're downright kooky for not basing it on the galaxy, but ce la vie. Presumably there's one of those too, and this just wins for boring social inertia reasons as much as for any technical ones.

image: https://geoscienceaustralia.github.io/ginan/images/ICRF-75pc...

wiki: https://en.wikipedia.org/wiki/International_Celestial_Refere...

Of course this doesn't really matter for the above musing since top/bottom would purely be conventional based on our viewpoint, but otherwise illuminating on the issue of understanding rotation directions across the universe.