Star Ejections?

[ryanneill]

I was reading MSN earlier and saw an article about how the believe solar system was scultped by a close encounter of another solar system... in the article a paragraph had me wondering something <br /><br /><blockquote><font class="small">In reply to:</font><hr /><p> Early chaos<br />There is no firm evidence that the sun ever interacted closely with another star, but many astronomers think the sun was probably born amid a tight huddle of stars, all of which formed out of the same gas cloud. Most stars in the galaxy are known to form in such clusters. The sun was later ejected from the cluster, the thinking goes.<p><hr /></p></p></blockquote><br /><br />How exactly do stars get ejcted from clusters or gas clouds? does something hit them or does it just get flung out by orbiting something sorta like what long range satellites do when they circle around the moon a few times to pick up speed?

 

[alokmohan]

Tidal gravity and other tug of war in gravity.

 

[CalliArcale]

To elaborate, yes, it is something like what deep space probes do to pick up energy (or, in some cases, to lose energy -- MESSENGER will make many gravity-assist flybies over the next decade to match velocity with Mercury so it can enter orbit). The interactions between protostars can push some stars away, and it's also possible for a massive star unrelated to the star cluster to just happen to zip by and deflect objects away from each other. Or both can happen. It would take a very long time, but then, the sun has been around for billions of years -- plenty of time for a lot to happen. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[Maddad]

Ryanneill <br />Stars in a group, such as our galaxy, orbit a common point. In this case it is the galactic center. How far they orbit is a measure of how much orbital energy they have. If they lose orbital energy then they'll fall into the center, and if they gain energy then they orbit further out. If they gain enough then then leave altogether; they have achieved escape velocity.<br /><br />Over time stars brush past one another. One will transfer some of its orbital energy to the other. One speeds up and the other slows down. The tendency is for the more massive star to give up some of its energy, and the lighter one gains it. This is one reason why we have a population of more massive star in the galactic nucleus. The flip side is that gradually the lighter stars gain orbital energy. Some take up larger orbits, and others take off into the intergalactic reaches of space on their own.

 

[thalion]

The Sun probably left its original cluster because its parent cluster was simply not massive enough to hold its together gravitationally. This is why most open clusters are relatively young.