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Dark matter probably is. Dark matter is matter. It gravitates. It obeys conservation of angular momentum. Unless the dark matter clump happened to form in a sp
by mikhailfranco 2y ago
Dark matter probably is.
Dark matter is matter. It gravitates. It obeys conservation of angular momentum. Unless the dark matter clump happened to form in a spherically symmetric contraction, it will be rotating, almost certainly coupled to the rotation of the galaxy.
- Sharlin 2y agoThe difference is that while the dark matter halo almost certainly has has net angular momentum, individual DM particles would not be coupled to the galaxy’s rotation to any meaningful degree, and would have essentially random velocities relative to a local corotating frame. The entire reason that spiral galaxies exist is that baryonic matter interacts electromagnetically and can dissipate kinetic energy via heat (photons). That causes matter to eventually flatten into a disc rotating more-or-less uniformly. In this sense a DM halo is similar to elliptical galaxies which certainly have net angular momentum, but their stars have essentially random orbital planes.
- codethief 2y ago> The difference is that while the dark matter halo almost certainly has has net angular momentum, individual DM particles would not be coupled to the galaxy’s rotation to any meaningful degree Does this take into account frame-dragging induced rotation?
- Sharlin 2y agoSpacetime is essentially flat on a galactic level for any general-relativity purposes. I'm pretty sure you can safely ignore frame-dragging here.