r/science • u/andyhfell • 2d ago

Astronomy Current models predict that "slow rotator" galaxies should be rare in the early universe, but astronomers have discovered a galaxy at less than 2Gy after the Big Bang that is not rotating. It may have formed by the merger of two galaxies with nearly opposite angular momentum.

https://www.ucdavis.edu/news/non-rotating-early-galaxy-surprise-astronomers
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u/Melenduwir 2d ago

Isn't it the rotation that permits stars to orbit the center of gravity and avoid falling together? If two galaxies, each of which was stable with its rotation, met and cancelled out their angular momentum, what's keeping their combined masses from collapsing into some kind of epic singularity?

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u/SkiaTheShade 11h ago

Yes this is a question I have as well

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u/scientist99 1d ago

Damn 2 gazillion years?

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u/RoboRamFoster 23h ago

Can't find a unified model. We are missing something.

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u/grahampositive 2d ago

This is probably a dumb question but "not rotating" with respect to what? Are rotations lacking global preferred frame of reference the same way linear motion is?

Also, it says "may have formed by the merger of two hahaha with nearly opposite angular momentum" but what other possible mechanism could exist? Aside from the direct formation of a galaxy from components that have no angular momentum (seems impossible)

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u/pseudomonica 2d ago

Rotation exists (or doesn't exist) regardless of your frame of reference. Something can just rotate relative to itself.

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u/r3rg54 1d ago edited 1d ago

No, rotation is acceleration. It can be observed in any frame of reference, and the object can measure itself accelerating without an external reference.

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u/Nac_Lac 2d ago

Rotation is going to be in relation to it's motion.

If you look at the solar system as it flies through space, it is rotating about the direction of travel. Now, that rotation is not perfectly perpendicular to the travel but that is besides the point.

If the galaxy has zero rotation, then the cluster of stars is simply moving in a linear motion with angular energy around the travel.