3 ms·
How well-defined is the angular velocity of a galaxy? Since it's not a solid disk, there's no reason for it to be the same for different regions. Is there any u
by ilyagr 9y ago
How well-defined is the angular velocity of a galaxy? Since it's not a solid disk, there's no reason for it to be the same for different regions. Is there any uniformity at all, e.g. do stars at the same distance from the center move at similar speeds?
Somebody else in the thread points out today our own son makes 4 revolutions around the galaxy center in a billion years, not 1.
- bmc7505 9y agoHow well defined is your son? Even if the group of atoms which he is composed of is not solid for 1 billion years, there is a way to approximate his average angular velocity around the center of the galaxy. They chose a bunch of stars on the outer rim of a galaxy, and they all had a similar angular velocity, despite large differences in their radii. Here they define it as the average angular velocity on the outermost edge of the galaxy.
- 8bitsrule 9y agoYou may find this helpful: https://en.wikipedia.org/wiki/Galaxy_rotation_curve https://en.wikipedia.org/wiki/Galaxy_rotation_curve If you look at a 33rpm spinning record, you'll see that any point on the edge of the label is moving a lot slower (linear speed) than the record's edge ... even though it has the same 'angular velocity' (33 rpm). But galaxies are not solid like a record, and as the article explains, "most stars in spiral galaxies orbit at roughly the same speed" (that's linear speed). So the edges 'fall behind.' (That was not recognized until about 1975.)