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WaxRubiks
2007-Jan-13, 03:47 PM
A frightning thought, that is, if a civilization evolved on a planet revolving around a star that was between galaxies.

Thier only hope of distant space fairing would be a faster than light warp drive thing.

So, are there any documented stars between galaxies?

StupendousMan
2007-Jan-13, 04:04 PM
A frightning thought, that is, if a civilization evolved on a planet revolving around a star that was between galaxies.

Thier only hope of distant space fairing would be a faster than light warp drive thing.

So, are there any documented stars between galaxies?

Yes, although it's a bit of nebulous topic: just where is the "outer edge" of a galaxy? How do you know that _this_ star is "in" the galaxy, but _that_ one over there is "outside"?

There has been a lot of interest in this topic over the past decade or so, since the motions of intergalactic stars can tell us something about the distribution of mass in intergalactic spaces. You can find many papers by going to the ADS system:

http://adsabs.harvard.edu/abstract_service.html

and typing into the "Abstract words" box the terms

intergalactic stars virgo cluster

Press the "Send Query" button and scan the list of returned articles. You'll be able to read most of the abstracts, and even the full text of some of the articles (especially if you choose the "astro-ph" links for each article).

Have fun!

Nereid
2007-Jan-13, 05:58 PM
There's also the recent stream of results from analysis of the huge SDSS database ... use 'field of streams' in a search engine - you'll get quite a few references to stars lost in inter-galactic Local Group space ...

Another useful search term: 'ICL' or 'IcL' (intra-cluster light).

For real loneliness, try being deep in a void, such as the Boötes void (http://en.wikipedia.org/wiki/Bo%C3%B6tes_void).

AGN Fuel
2007-Jan-14, 10:52 PM
A frightning thought, that is, if a civilization evolved on a planet revolving around a star that was between galaxies.

Thier only hope of distant space fairing would be a faster than light warp drive thing.

So, are there any documented stars between galaxies?

From the first time I saw a simulation of colliding galaxies with the resultant ejection of many stars into intergalactic space, I always thought that any civilisation on a planet orbitting such a star would have the most utterly magnificent view of their former home...

kmarinas86
2007-Jan-16, 06:15 AM
There are not much metals between the galaxies (not as many supernovas), and therefore, not as likely for a space faring civilization to come from there (or to there for that matter).

AGN Fuel
2007-Jan-16, 06:29 AM
There are not much metals between the galaxies (not as many supernovas), and therefore, not as likely for a space faring civilization to come from there (or to there for that matter).

True - but just imagine a star gently ejected from a galaxy due to such an interaction together with its retinue of planets (assume they are able to maintain a stable orbit throughout the process), just as the first spark of life was emerging. By the time intelligent life evolved...

With 100 billion galaxies of 100 billion stars each, I'm not going to say it couldn't happen! And they don't necessarily have to be spacefaring to appreciate the view - they just need the ability to look up! :)

Tim Thompson
2007-Jan-16, 06:58 AM
Globular cluster NGC 2419 (http://www.seds.org/messier/xtra/ngc/n2419.html) is about 90 kpc (290,000 ly) away. It is called The Intergalactic Wanderer. Despite being considerably more distant than the Magellanic Clouds, it is probably still bound gravitationally to the Milky Way, but only barely I think. There is a considerable population of intergalactic stars between M81 & M82, mostly stripped out of M82 by the collision (Sun, et al., 2005 (http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005ApJ...630L.133S&db_key=AST&d ata_type=HTML&format=&high=4366fa465127707)). Zibetti, et al., 2005 (http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005MNRAS.358..949Z&db_key=AST&d ata_type=HTML&format=&high=4366fa465127707) study the intracluster light, produced by intergalactic stars, in 683 galaxy clusters from the Sloan Digital Sky Survey. It certainly seems that intergalactic stars are common.

JohnD
2007-Jan-16, 12:18 PM
Frog,
Why would it be a more daunting prospect than our situation?
We have no reasonable "hope of distant space fairing" unless some supraluminal drive can be invented. Generation ships? I doubt them - they cost too much.

You also made me remember Asimov's 'Nightfall', where a society was exposed to the stars at night for the first time - and collapsed. An inter-galactic system would not be in that position, and multiple suns inflict chaotic orbits, so life, let alone civilisation would be unlikely, but how about a star, or stars, within a dust cloud? Their birth would clear a bubble in the dust - would that clear to the Universe before civilisation occured? If it took longer, what would they think of their first peeps through the veil?

John

WaxRubiks
2007-Jan-16, 12:28 PM
well, I think that there would be a way for mankind to spread to the stars in the milkyway sub-lightspeed but that would be slightly harder for a civilization between the galaxies.

Perhaps they could send out robot ships with equipment to generate embryos and raise children to adult hood when the ships got to the galaxy.


I have my doubts that future mankind or some ET would have much need for planets etc. being quite happy to live in some sort of VR, certainly once the stars all run out of energy any ETs left will have to withdraw into artifical worlds either cities underground or VR worlds.

GOURDHEAD
2007-Jan-16, 02:04 PM
well, I think that there would be a way for mankind to spread to the stars in the milkyway sub-lightspeed but that would be slightly harder for a civilization between the galaxies. The system described at:http://home.comcast.net/~mbmcneill7/ can evolve within 10,000 years into one that can accommodate sub-light speed intergalactic travel by "taking a suitable star along with the tavellers and their planets". The physics is known; the engineering is left to do as an exercise for the readers---all three of them.

neilzero
2012-Dec-17, 06:03 AM
Reasonably, there are lots of class m stars = just barely fusing hydrogen between the galaxies. Possibly there are even more brown dwarf "stars" in the voids. Possibly 1% as many white dwarfs, nuerton stars and black holes. Stars with briefer light output are likely leaving their galaxy at faster than escape velocity, but they will be off main sequence, before they are far enough out of their galaxy to be distinctly in the void. A star forming gas cloud in the void, if we could detect it would likely be classed as a miniture galaxy/ how many of these have been identified with high confidence?
Perhaps an interesting number is how many bodies with more mass than Jupiter are distinctly in the voids? Interesting because very advanced beings could live on many of the smaller bodies orbiting the Jupiter plus bodies. Let's assume one per million cubic light years, so the 10*30 = a decillion cubic light years closest to Earth has 10*24 of these in the voids near the milky way galaxy, which is likely almost the total of these kinds of bodies distinctly inside the near by galaxies. 10*24 is a million times a million times a million times a million. 10*30 is a cube 10 billion light years on an edge, so it is several percent of the known universe. Those farther from Earth will likely remain unintersting and unknowable very long term. Neil

Jens
2012-Dec-17, 06:35 AM
A frightening thought, that is, if a civilization evolved on a planet revolving around a star that was between galaxies.


I also think it's not that far from our situation. But more to the point, why is it frightening? We have had civilizations going back five or six thousand years, and I don't think it's every been particularly frightening that we couldn't colonize another planet.

novaderrik
2012-Dec-17, 09:26 AM
would a civilization that rises on a planet orbiting a star that doesn't really "belong" to a galaxy ever be tempted to even think about trying to figure out how to reach another star system?

we are surrounded by stars, with the closest of them being just close enough that we could conceivably send people on a journey that would get them there within a generation or so if we really put our hearts and minds to it.. for someone out in the middle of nowhere, they would know that it would take millions or even billions of years just to get to the nearest stars unless they came up with a way to cheat physics and go much faster than light.

Githyanki
2012-Dec-18, 04:34 AM
If planets and asteroids can be ejected from solar-systems, so can stars, nebulas etc. from galaxies.

Life in an ejected system would be pretty stable. No super-novas, no gamma-ray bursts, no close encounters with other stars to perturb the Oort-cloud and send comets crashing into them. The only thing in the night-sky besides perhaps a moon and the other planets would be an awesome view of the galaxy they left.

slang
2012-Dec-18, 06:27 AM
Reasonably

Speaking of reasonable, were you aware you're answering an almost 6 year old question?

kzb
2012-Dec-18, 01:17 PM
Here's an interesting paper that is connected (vaguely) with the topic. It is about plotting the galactic rotation curve, but the interesting point to me was that they have detected stars out to 24kpc galactic radius. These stars are not old Pop II, halo or thick disk stars, they are intermediate-age thin-disk stars.

The type of star used for this study are not likely to host habitable planets themselves; the connection with this thread lies with the fact that they are probably a tracer of a large population of less luminous stars. These thin disk stars may well have habitable planets, way beyond the traditional edge of the Milky Way galaxy.

So although any aliens on these planets are still members of our galaxy, they could be 50,000 light years further out from the centre than we are. They still have the characteristics of between-galaxy civilisations -they are more likely to actually exist as well.


Extension of the C star rotation curve of the Milky Way to 24 kpc Battinelli et al, Dec 2012

http://arxiv.org/abs/1212.1116

Hornblower
2012-Dec-18, 01:42 PM
A star with a planetary system like ours could be ejected into intergalactic space by a close encounter with another galaxy without necessarily disrupting the orbits of the planets, and evolving primitive lifeforms might never know the difference. Had such an encounter happened with our system a billion years ago, we might be looking at a night sky nearly devoid of naked eye objects other than the planets and some smudges of diffuse light.

Jeff Root
2012-Dec-19, 03:13 AM
A star with a planetary system like ours could be
ejected into intergalactic space by a close encounter
with another galaxy without necessarily disrupting
the orbits of the planets ...
Could it? It seems to me that it would require a
close encounter between the Sun and a very massive
star in the other galaxy, in which the Sun's speed
relative to the center of the Milky Way changes
greatly and suddenly, sending the planets off in all
directions.

-- Jeff, in Minneapolis

ASTRO BOY
2012-Dec-19, 03:18 AM
In the right circumstances I imagine a BH could kick a star out of a galaxy too....

Thanatos
2012-Dec-19, 06:55 AM
It is fairly well established that 'rogue' stars are routinely voted off the island by their parent galaxy. Chances are they are fairly abundant, but, still comprise a decided minority of stars in the universe.

kzb
2012-Dec-19, 12:20 PM
It is fairly well established that 'rogue' stars are routinely voted off the island by their parent galaxy. Chances are they are fairly abundant, but, still comprise a decided minority of stars in the universe.

Yes I have read that also. I wonder if there is another factor, and that is that small stars, brown dwarfs and lone planets should be preferentially ejected over massive stars. The dim objects are obviously hard or impossible to detect at large distance, so maybe there are more of them than we think out there.

On the other hand, the change in velocity required to completely escape a galaxy like ours is so great that maybe only encounters with the central black hole or the very most massive stars will do. In that case, maybe there is no detectable mass selection for these ejectees.

I think Jeff has a good point: in order to keep the planets in the same orbits, surely they'd need to experience a gravitational potential that is negligibly different to that experienced by their parent star during the encounter. Probably there is something published on this, but to me it does not seem likely that planetary orbits could be unaffected.

Hornblower
2012-Dec-19, 02:35 PM
Could it? It seems to me that it would require a
close encounter between the Sun and a very massive
star in the other galaxy, in which the Sun's speed
relative to the center of the Milky Way changes
greatly and suddenly, sending the planets off in all
directions.

-- Jeff, in Minneapolis

I don't think a close encounter with an individual star is needed. A flyby of the dense core of the intruding galaxy on a suitable crossing path should do it, with a minimum separation of some thousands of lightyears. The same total delta V would be accomplished over a vastly longer time than in the case of an encounter with a single star, so the motion would be much gentler, and the tidal gradient across the planets' orbits would be vanishingly small. My orbital mechanics math is pretty rusty, but with some brushup study I should be able to get some ballpark figures on this.

ngc3314
2012-Dec-19, 05:45 PM
Even gentler. Simulations of galaxy encounters very often show tidal tails, some stars of which may pick up enough velocity to become unbound (depending on the halo mass and its distribution). As well as for stars passing close to the intruder core, this process is most effective, for example, when a star's initial orbit is at an angular rate that closely matches the intruder's for a long time, so the tidal acceleration is cumulative over ~100 million years. All the disk stars in a large area wold feel practically the same effects, planets and all. In galaxy clusters, the total fraction of stars liberated from galaxies has been estimted as high as 10-25% (seen in diffuse light, individual red giants, and planetary nebulae).

chornedsnorkack
2012-Dec-19, 06:33 PM
How did the two Magellanic Clouds form? And did the process expel any individual stars?

Jeff Root
2012-Dec-19, 09:37 PM
Hornblower, ngc3314,

That makes sense. And it fits what little I've seen of galaxy
interactions. I'm sure your're right: When wholesale disruption
of one galaxy by another occurs, entire solar systems would
be flung away nearly unchanged, in very large numbers. It's
just that the large numbers mean they'd mostly still have a
lot of companions not too far away.

-- Jeff, in Minneapolis

sjw40364
2012-Dec-20, 11:42 PM
Depends. Some claim that galaxies are full of billions of stars, some claim they ain't. Check out the link, an interesting paper, that so far I have not been able to show his supposition about distances to be incorrect.
https://11dc5d5d-a-62cb3a1a-s-sites.googlegroups.com/site/cosmologyquest/files/AstronomyDec28-2008.pdf?attachauth=ANoY7cpBihOzxFNesbxNloWOVwQpLC 863IzsDXIFXbH0Yn_7j0I4BHgcaU11Yq0ydfiSZHEGdkRhN__3 vzs9yYeH4NuSKJ_MGRbKyybrPCPn2gTkAQYFYQNxVvLIUkasDl q0r4DSfPFhjr3YcdGf4-rzLCFlsSaeqpGpThw1Yw90X5P4Os3MXgWU7H2weGr1bB5W8Rz6 dUFzZzMocUAMd5zcG9iKelWPS5xVYgG1OfBb5TMXeDUFMoY%3D&attredirects=1

Van Rijn
2012-Dec-21, 02:22 AM
Depends. Some claim that galaxies are full of billions of stars, some claim they ain't.


It depends on the galaxy. Some dwarf galaxies have fewer than a billion stars, but the Milky Way has hundreds of billions, and there are larger galaxies than the Milky Way.

Van Rijn
2012-Dec-21, 03:36 AM
Check out the link, an interesting paper, that so far I have not been able to show his supposition about distances to be incorrect.
https://11dc5d5d-a-62cb3a1a-s-sites.googlegroups.com/site/cosmologyquest/files/AstronomyDec28-2008.pdf?attachauth=ANoY7cpBihOzxFNesbxNloWOVwQpLC 863IzsDXIFXbH0Yn_7j0I4BHgcaU11Yq0ydfiSZHEGdkRhN__3 vzs9yYeH4NuSKJ_MGRbKyybrPCPn2gTkAQYFYQNxVvLIUkasDl q0r4DSfPFhjr3YcdGf4-rzLCFlsSaeqpGpThw1Yw90X5P4Os3MXgWU7H2weGr1bB5W8Rz6 dUFzZzMocUAMd5zcG9iKelWPS5xVYgG1OfBb5TMXeDUFMoY%3D&attredirects=1

That was discussed previously here:

http://cosmoquest.org/forum/showthread.php/113525-A-Revolution-in-Astronomy

You should be able to see a number of issues with the claims mentioned in the thread (for others, this guy is claiming stars are actually planets orbiting the sun :rolleyes:). There were so many obvious problems it looked like an Onion parody.