richk@tektronix.UUCP (06/14/83)
Last nights COSMOS reminded me of a question I've had for some time:
It was stated that stars are born in groups. Later they move off into
seperate orbits. Thus, the suns siblings could well be on the other
side of the galaxy from us.
It seems to me that they would tend to stay together rather than move
well away from each other. If they were all born from the same gas cloud,
they should all have about the same motion as the cloud had around the
center of the galaxy. (since their distribution covers a very small
amount of space vs the size of the cloud's orbit.) I think their
gravitational attraction would also tend to keep them together.
What is it that spreads these stars out? Close encounters with other
stars? That doesn't seem too likely. There would have to a lot of
encounters to spread them all out. Internal encounters seem to be too
limited in nature to quickly disorganize the cluster. Maybe close
encounters with demented astronmers? All stars hate each other?
Anyone out there know the real reason?
Richard
uucp: {ucbvax,decvax,chico,pur-ee,cbosg,ihnss}!teklabs!tektronix!richk
CSnet: richk@tek
ARPAnet:richk.tek@rand-relayKFL%MIT-MC@sri-unix.UUCP (06/17/83)
From: Keith F. Lynch <KFL @ MIT-MC> Date: 13 Jun 83 23:00:16-PDT (Mon) To: physics @ Sri-Unix From: harpo!floyd!vax135!cornell!uw-beaver!tektronix!richk @ Ucb-Vax Subject: 'Births of stars and their orbits' It was stated that stars are born in groups. Later they move off into seperate orbits. Thus, the suns siblings could well be on the other side of the galaxy from us. What is it that spreads these stars out? Close encounters with other stars? That doesn't seem too likely. There would have to a lot of encounters to spread them all out. Internal encounters seem to be too limited in nature to quickly disorganize the cluster. Maybe close encounters with demented astronmers? All stars hate each other? Anyone out there know the real reason? I believe it is because some of the stars are closer to the center of the galaxy and thus are in closer and faster orbits. Another way of saying this is to say that they are seperated by the tidal force of the center of the galaxy, i.e. we are within the galaxy's Roche limit. I think this is also why most (all?) nebulas are only a few thousand years old. They are pulled apart in not much more time than that. ...Keith