# Are there stars in intergalactic space? **URL:** \ **Category:** Factual Questions\ **Created:** [March 31, 2009, 11:28am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408 "2009-03-31T11:28:11Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [April 3, 2009, 4:23pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/41 "2009-04-03T16:23:38Z")
> [@ralph124c](#): > > As the universe expands, galaxies move farther apart. So how is it possible that two galaxies would ever collide? > Anyway, suppose two do collide-would some starts get ripped away and flung out into empty space? Well, most galaxies are moving apart, but most of them are doing it as clusters that are bound together by gravity. The Big Bang may have started everything out in a straight line (though I’m not even sure if we know that for a fact), but gravity wants to pull things together. Within the clusters of galaxies, they could be traveling in just about any direction at this point in time, even directions that could cause a collision. One way to think about it is like throwing a baseball up. It’s moving away from the Earth when it starts, but gravity turns the path in a parabola that causes it to collide with the Earth again. And simulations of galaxy collisions do show large numbers of stars flung off into deep space. If you do some Google searches, you should be able to find animations of it. ---
**Author:** ![flex727](https://avatars.discourse-cdn.com/v4/letter/f/258eb7/32.png) [@flex727](https://boards.straightdope.com/u/flex727)\ **Post date:** [April 3, 2009, 5:21pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/42 "2009-04-03T17:21:08Z")
> [@ralph124c](#): > > Anyway, suppose two do collide-would some starts get ripped away and flung out into empty space? [This site](http://www.galaxydynamics.org/) has some fantastic supercomputer simulations and modeling of galactic collisions. If you have the time and bandwidth, download the full resolution videos (rather than the YouTube versions) and be prepared to be mesmerized. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [April 3, 2009, 6:16pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/43 "2009-04-03T18:16:13Z")
> [@Q.E.D](#): > > Yes, keep beating that horse. It might not _really_ be dead. Butthurt much? ---
**Author:** ![SweetLucy](https://avatars.discourse-cdn.com/v4/letter/s/bcef8e/32.png) [@SweetLucy](https://boards.straightdope.com/u/SweetLucy)\ **Post date:** [April 4, 2009, 4:44am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/44 "2009-04-04T04:44:36Z")
There’s an Arthur C. Clarke story about a lone planet floating around in intergalactic space, “Crusade.” ---
**Author:** ![Lust4Life](https://avatars.discourse-cdn.com/v4/letter/l/ecc23a/32.png) [@Lust4Life](https://boards.straightdope.com/u/Lust4Life)\ **Post date:** [April 4, 2009, 1:03pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/45 "2009-04-04T13:03:49Z")
> [@ralph124c](#): > > As the universe expands, galaxies move farther apart. So how is it possible that two galaxies would ever collide? > Anyway, suppose two do collide-would some starts get ripped away and flung out into empty space? Our galaxy and the Andromeda galaxy are on a collision course as a M of I. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [April 4, 2009, 1:55pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/46 "2009-04-04T13:55:55Z")
> [@ralph124c](#): > > As the universe expands, galaxies move farther apart. So how is it possible that two galaxies would ever collide? > Anyway, suppose two do collide-would some starts get ripped away and flung out into empty space? As I understand it, basically, due to [gravity](http://en.wikipedia.org/wiki/Colliding_galaxies). ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [April 4, 2009, 2:52pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/47 "2009-04-04T14:52:54Z")
> [@KneadToKnow](#): > > As I understand it, basically, due to [gravity](http://en.wikipedia.org/wiki/Colliding_galaxies). Escape velocity from the Milky way is on the order of [550 km/sec](http://arxiv.org/abs/astro-ph/0611671) The Hubble constant for expansion is about 70.1 ± 1.3 (km/s)/Mpc. Thus Milky way sized galaxies would have to be separated by about 7.8 megaparsecs (25.6 million light years) apart in order to for the expansion of space to free them from each others gravity. Galaxies are much more closely spaced than that. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 5, 2009, 4:38am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/48 "2009-04-05T04:38:32Z")
> [@](#): > > Our galaxy and the Andromeda galaxy are on a collision course as a M of I. I wish people would quit quoting this as established fact. All we know for certain is that we’re currently approaching each other. But this does not imply that we’re going to collide: It’s rather more likely that we’ll just peacefully pass by each other. In fact, the two galaxies have probably passed close by each other this way several times since they were both formed. ---
**Author:** ![Rolken](https://avatars.discourse-cdn.com/v4/letter/r/df788c/32.png) [@Rolken](https://boards.straightdope.com/u/Rolken)\ **Post date:** [April 5, 2009, 5:09am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/49 "2009-04-05T05:09:35Z")
To clarify, we know that Andromeda is moving towards the Milky Way radially through fairly straightforward observations of redshifting (err blueshifting), but “side-to-side” tangential velocity is harder to pin down. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [April 5, 2009, 9:53am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/50 "2009-04-05T09:53:22Z")
> [@Rolken](#): > > To clarify, we know that Andromeda is moving towards the Milky Way radially through fairly straightforward observations of redshifting (err blueshifting), but “side-to-side” tangential velocity is harder to pin down. My understanding is that given the amount of radial velocity, for the two galaxies to pass without interacting, they would have to be unbound gavitationally. There’s probably enough tangential velocity that the two will make a small loop before they collide. But they’ll be close enough that there will be tidal interactions which will steal orbital energy and cause the collision. It’s probably true that the two galaxies have looped around each other two or three times since they formed, but that’s not enough for the orbits to have stablized. The above is based on a fairly recent article in Sky&Telescope which was based on computer simulations. But since then it’s been found that the Milky Way is more massive that was previously thought. However, the additional mass most likely means the collision will occur sooner than previously expected. ---
**Author:** ![Lust4Life](https://avatars.discourse-cdn.com/v4/letter/l/ecc23a/32.png) [@Lust4Life](https://boards.straightdope.com/u/Lust4Life)\ **Post date:** [April 6, 2009, 9:52am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/51 "2009-04-06T09:52:09Z")
> [@Chronos](#): > > I wish people would quit quoting this as established fact. All we know for certain is that we’re currently approaching each other. But this does not imply that we’re going to collide: It’s rather more likely that we’ll just peacefully pass by each other. In fact, the two galaxies have probably passed close by each other this way several times since they were both formed. I got this from BBCs “The Sky at Night”,usually considered a factually correct source. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [April 6, 2009, 10:29am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/52 "2009-04-06T10:29:06Z")
> [@Lust4Life](#): > > I got this from BBCs “The Sky at Night”,usually considered a factually correct source. Nobody in the mainstream media understands science, technology, or the culture surrounding either.\* \*(This rule of thumb is accurate out to at least two decimal places, and it always has been.) ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [April 6, 2009, 11:26am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/53 "2009-04-06T11:26:49Z")
> [@Derleth](#): > > Nobody in the mainstream media understands science, technology, or the culture surrounding either.\* > > \*(This rule of thumb is accurate out to at least two decimal places, and it always has been.) Sir Patrick Moore may be a bit of a statistical outlier as far as “mainstream media”, though. ---
**Author:** ![ivan\_astikov](https://avatars.discourse-cdn.com/v4/letter/i/58f4c7/32.png) [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)\ **Post date:** [April 6, 2009, 11:44am UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/54 "2009-04-06T11:44:25Z")
Remember the example of the universe being like a balloon with the galaxies represented by magic marker dots, and how as it is blown up, the dots move away from each other? Does anyone want to explain how these ‘dots’ get to cross each others paths? ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [April 6, 2009, 12:47pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/55 "2009-04-06T12:47:11Z")
> [@ivan\_astikov](#): > > Remember the example of the universe being like a balloon with the galaxies represented by magic marker dots, and how as it is blown up, the dots move away from each other? > > Does anyone want to explain how these ‘dots’ get to cross each others paths? They are not magic marker dots, they are ants and they move around following their own rules (gravity) ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [April 6, 2009, 2:55pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/56 "2009-04-06T14:55:01Z")
> [@ivan\_astikov](#): > > Does anyone want to explain how these ‘dots’ get to cross each others paths? [Here’s a start](http://www.merriam-webster.com/dictionary/oversimplification). ---
**Author:** ![ivan\_astikov](https://avatars.discourse-cdn.com/v4/letter/i/58f4c7/32.png) [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)\ **Post date:** [April 6, 2009, 3:16pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/57 "2009-04-06T15:16:31Z")
> [@Sapo](#): > > They are not magic marker dots, they are ants and they move around following their own rules (gravity) Here’s how I saw it. The Big Bang occurs and all matter is sent blasting from a specific point, in every direction. At some point, the mysterious property gravity, begins to draw some of the matter together, which developed into blobs we call galaxies. Such was the velocity these particles were travelling from their initial point, that these galaxies continued travelling “outwards”, and even seem to be speeding up. So, if you rewound all these galaxies to their starting point, when would their paths have criss-crossed, and why are they likely to start doing it in the future if they haven’t already? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [April 6, 2009, 4:03pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/58 "2009-04-06T16:03:07Z")
> [@ivan\_astikov](#): > > The Big Bang occurs and all matter is sent blasting from a specific point, in every direction. This is incorrect. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [April 6, 2009, 4:37pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/59 "2009-04-06T16:37:16Z")
I am well over my head here but here it goes. The Big Bang was not a firecracker explosion that sent matter away on an empty space. There was no space there to begin with. Have you seen those “art” pieces where they squirt paint on a canvas and then they make it spin and the paint spreads over the blank parts of the canvas? The Big Bang was not like that. The canvas itself is growing. That is how the balloon example works. It is not that the matter is the balloon and it is expanding propelled by an explosion filling the empty room. The balloon is the universe expanding. Gravity won’t make the balloon collapse again. Gravity moves the dots around the balloon surface. Am I making any sense or just further confusing this? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 6, 2009, 8:31pm UTC](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408/60 "2009-04-06T20:31:34Z")
> [@](#): > > Gravity won’t make the balloon collapse again. This appears to be the case, but it’s a consequence of the particular conditions of the Universe, not the way the physics operates. A decade ago, it was not known whether gravity would cause the balloon to collapse eventually or not. [Previous page](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408.md?page=2) [Next page](https://boards.straightdope.com/t/are-there-stars-in-intergalactic-space/491408.md?page=4)