In Do black holes rotate east to west?, Chronos writes
How far before the directions are randomized? Are spins within the Milky Way, including our solar system, more-or-less aligned with the galactic rotation? What about within our local cluster? Is Andromeda’s rotation similar to the Milky Way’s, or is it independent?
Andromeda and the Milky Way are in entirely different planes. I believe they are the only regular galaxies in the local group.
AFAIK, stars’ inclinations are essentially random. Stars in a multiple star system are probably going to be aligned, but not necessarily.
There is another spiral galaxy in the local group, M33 the Pinwheel galaxy. It’s plane does not seem to be aligned with either our galaxy or the Andromeda galaxy.
Even looking on the scale of a single galaxy, the disk of a spiral galaxy (such as ours) clearly shows a preferred spin direction, but the globular clusters which surround it can (and do) orbit in any which way. Certainly, by the time you get to multiple galaxies, there’s no corellation.
Chronos:
Does the “preferred spin direction” of a spiral galaxy imply that the stars and solar systems within that galaxy also tend to have the same spin direction? If so, to what extent? Do “most” stars spin in “approximately” the same direction? Is the similarity in star spin directions within in a galaxy quantified? Are stars that are neighbors more likely to spin in the same direction than stars that are widely seperated, but still in the same galaxy? Are stars in the center more likely to be aligned? On the periphery? Well? Huh? Huh? Well?
I don’t think so, zut, but I’ll have to check up on it. In any event, the corellation wouldn’t be very strong: Our own solar system is inclined at a fairly large angle to the galactic plane. I’ll post more on this this evening.
There’s two ways to define a north pole. One is that the object is rotating counterclockwise when viewed from above the pole. The other is that the north pole is the one pointing towards the north ecliptic hemisphere.
The IAU had chosen the second of these definitions for astronomical objects. Which means that some objects rotate clockwise about their north pole and thus rotate retrograde. Besides Uranus and Venus, Pluto and the Milky Way galaxy rotate retrograde.
After checking my watch, I can only conclude that I’ve been stood up.
But, in any case, the conclusions are that: 1) spins of individual solar systems are not neccessarily aligned with the spin of the galaxy as a whole, and 2) there is little or no correlation between the spin directions of adjacent solar systems. Correct?
Which means that there is an organization of spin direction on the scale of the solar system, but no organization on the “local group” scale, but there is organization on the galactic scale. Interesting. Is the effect that causes a galactic spin different that what causes the spin in the solar system? If it’s the same effect, it seems that we wouldn’t see the isotropy on the “local group” scale.
Sorry, zut, it seems that the numbers are a bit harder to find than I thought they would be… If I do dig up some good inclinatin data, I’ll post it, but I hereby retract any promises on when I’ll get them.