Inter-galactic stars

[RobSay]

A thought occured to me as I was looking at a variety of Andromeda pictures - the noise was bothering me.. These pictures always have numerous other stars which as a general rule will be in our immediate* vicinity (not so sticky out nondescript spiral arm that we are). The noise will moslt be local stars in the bit of our galaxy between us and Andromeda. Any other DSO has the same noise but the further away it is, the less noise there is since the arc being observed is smaller. Consequently the local stars (having a uniform distribution density) are 'spread out'.

Given the generally accepted evidence for galactic collision - are there any known examples of stars that have escaped their parent galaxy? (a collision would be sure to throw things out as well as in) - is any of the 'noise' truly intergalatic and is anybody looking for these, what could we learn from finding one (or more)?

My though is that it would be a very very hard thing to do. What would be the definition of extra-galactic stars - in comparison to the solar system boundary definition? Could anything available in the local group have gone 'extra-galactic' or are we so packed in that any escapees would still be interacting?

Enlighten me - Learned papers, textbook definitions, wacky theories, co-ordinates - anything

ta

Rob

[brianb]

There are certainly known examples of stars in the Magellanic Clouds which are moving far too fast to be gravitationally bound. In dense clusters gravitational "slingshotting" can build up speed. There is also some evidence that when sufficient material is thrown out of the vicinity of supermassive black holes as polar jets, this material can later condense into stars which will be moving too fast to be gravitationally bound to the parent galaxy.

You can't think of a collision of galaxies as being like a train wreck - most of the material only reacts gravitationally, there isn't much actual collision between objects. Colliding gas clouds may be locally compressed to the point where star formation can begin but there isn't much actual exchange of momentum.

Stars will not form in intergalactic space because there isn't the material there that's needed.

[Space Bat]

Yes it is possible to find stars outside galaxies and what is more remarkable is that stella birthplaces can occur outside galaxies in what could be termed in the middle of nowhere.

Hanny's Voorwerp is one such anomoly which may be one of millions of stella objects out there that can be birthing stars never to be bound by a galaxy.

[RobSay]

Thanks for the responses. I had presumed there were non-gravitationally bound stars and that the relative velocity of some galaxies had been measured but not individual stars.

I was unaware of star formation outside of galaxies. Hannys Voorwerp - fanastic stuff, very interesting (and a good story). I'm sure there's plenty of other stuff out there yet to be found.

cheers

Rob

[MightyMidget]

There are many ways intergalactic starforming regions may form. The following link has much information on this subject:

http://star-forming-dwarfs.org/files/boquien_presentation.pdf

[phat tony]

bat, if we had a star without bonds as you say could it survive for a long time or would its life span be short????. another question.... have we any evidence of two stars colliding or even two black holes. what would happen if two black holes collided, would the join or have a very bad reaction with each other?????????????????????

[JulianO]

bat, if we had a star without bonds as you say could it survive for a long time or would its life span be short????. another question.... have we any evidence of two stars colliding or even two black holes. what would happen if two black holes collided, would the join or have a very bad reaction with each other?????????????????????

The star in intergalactic space would do just fine. Most stars in our galaxy live and die without interaction with other stars. They don't need a support system, so such wandering stars would live out their natural life and then extinguish in their chosen manner.

We have good evidence stars collide, some of the type 1a supernovas are thought to be from two white dwarfs colliding. In galaxy mergers occasionally (but quite rarely) stars collide (its predicted when the andromeda galaxy collides with the milky way, there might be 3-7 star collisions).

When black holes join, they consume each other. I think as they get close to merger they give off large amounts of gravitational waves. I've also got an idea that its either neutron stars or black holes colliding that may be one source of gamma ray bursts, but I forget the details.