What's between galaxies?

[JasonChapman]

I have a question for the resident astronomers on space.com. We all know that there are billions of galaxies in our universe, separated by vast amounts of space. However is it possible for stars to exist on their own without a galaxy, or perhaps a rogue star with a solar system, is there nothing but empty space between galaxies.

 

[neilsox]

Surely the edges of galaxies are fuzzy, then thinning about exponentially. Perhaps the half way point between galaxies occasionally has a millionth the mass of the average mass within 100 light years of our solar system. More is likely typical.
Objects and particles traveling away (approximately) from the center of a galaxy typically keep going for at least 100 light years before they fall back into the galaxy like cannon shell at the top of it's trajectory. The 200 light years travel outside the galaxy could last a billion years, but somewhat less is likely typical. Outside for a million times a million years is likely extremely rare and has not happened yet as the Universe is only 13.7 billion years old. Like planets, galaxies do sweep up some of the mass that they collide with as they travel. Most galaxies do travel and are typically orbiting the other galaxies in their local group of galaxies. We think the local groups are traveling in random directions vectorially added to the expansion of the Universe, which is why rare galactic groups show blue shift rather than red shift.
Photons and neutrinos, are only slowed very slightly by the average gravity of a galaxy, so they may average 1% of the number typical in our Oort cloud. What is lacking almost entirely is stars that have ten or more times the absolute luminosity of our sun, as most of these become compact stars, before they leave the galaxy.
Are there other mechanisms besides sling shot maneuvers at work to get mass between the galaxies? Neil

 

[ramparts]

Stars do exist between galaxies, although only extremely rarely. They usually get flung out into the intergalactic void during collisions between galaxies, although there are some stars within galaxies which (due to gravitational interactions) have high enough velocities to leave.

But mostly, between galaxies there's gas and dark matter. And empty space. Lots of empty space.

 

[JasonChapman]

Stars do exist between galaxies, although only extremely rarely. They usually get flung out into the intergalactic void during collisions between galaxies, although there are some stars within galaxies which (due to gravitational interactions) have high enough velocities to leave.

But mostly, between galaxies there's gas and dark matter. And empty space. Lots of empty space.

I just watched the last part of Hawkins Universe, and he mentioned that galaxies collide, I was just wondering do things like comets travel between galaxies, or does gravity prevent this.

 

[MeteorWayne]

It's HAWKING !!!

I would say it is more unlikely that comets can be ejected into intergalactic space on their own, but it a stellar system is ejected from a galaxy, it's possible some would survive. However, they most likely would remain bound to their star most of the time.

Of course, anything is possible, so we can assume that somewhere there are stars, planets, asteroids and comets in between galaxies. Just not very many.

 

[BurgerB75]

In regards to a comet being ejected, is there an escape velocity from the galaxy? Similar to an escape velocity from other gravity wells.

 

[thnkrx]

There are a number of low metallicity 'subdwarf' type stars with extremely eccentric galactic orbits (eccentricity of 90%, give or take a few percentage points) that take them well into intergalactic space. I seem to remember a couple of them, according to some calculations, as having essentially hyperbolic (no return) 'orbits'. There is what might be termed a sort of rough 'association' of these stars scattered over many hundreds of light years, currently passing through the same galactic region as our sun. The flip side of this, though, is that the galactic orbits of some of these stars takes them very nearly to the galactic core.

 

[MeteorWayne]

In regards to a comet being ejected, is there an escape velocity from the galaxy? Similar to an escape velocity from other gravity wells.

Yes there is, as there is for any central (or more properly barycentral) mass. But unless the star is ejected, it's very unlikely an ejected comet would exceed the galactic escape velocity.

 

[BurgerB75]

Thanks MW.

 

[Floridian]

Scientists have been simulating the effects of an intergalactic trip on humans in a controlled environment in Russia. Volunteers are to begin the 1,230,345,343 year simulation in August.

 

[bushwhacker]

Scientists have been simulating the effects of an intergalactic trip on humans in a controlled environment in Russia. Volunteers are to begin the 1,230,345,343 year simulation in August.

All i can say is i hope they bring plenty of beer and women on that billion year test

 

[trumptor]

If they're Russian, they'll maybe need the beer to rehydrate themselves after a night of drinking :lol:

Seriously though, imagine a stellar system like ours in the emptiness of intergalactic space. If there were a civilization in that situation, can you imagine their fascination with galaxies and their scientific debates on the possibilities of life within galaxies. Also, their hope of interstellar travel would be greatly hampered.

 

[robnissen]

If there were a civilization in that situation, can you imagine their fascination with galaxies and their scientific debates on the possibilities of life within galaxies.

Their night sky wouldn't be much. A handful of planets and a few large and small magellanic cloud type objects and that would be about it. Would be hard to do much stellar navigation. (Technically, stellar navigation would be impossible, seein as how there would be no stars.)

 

[Tony_C]

We can see the Andromeda galaxy with the naked eye from Earth. So, depending on the size of nearby galaxies, some kind of night light reference navigation might be possible from a planet residing in intergalactic space. It would certainly be dark, but if the planet rotates then knowing where the galaxy rises and sets, and through experience its trace on the sky, it could easily provide some reference line, and two of them (or one in combination with a reflective moon) might provide some kind of grid for navigation. I'm just sayin'.

 

[lakeshow]

If there were a civilization in that situation, can you imagine their fascination with galaxies and their scientific debates on the possibilities of life within galaxies.

Their night sky wouldn't be much. A handful of planets and a few large and small magellanic cloud type objects and that would be about it. Would be hard to do much stellar navigation. (Technically, stellar navigation would be impossible, seein as how there would be no stars.)

Yes, but imagine they develop telescope technology. Then they look out and start spotting galaxies with BILLIONS of stars compared to their "galaxy" of 1 lonely star. Trumptor is right, they would be beyond fascinated.

sidenote: i thought some of the spots of light we see at night are galaxies... maybe not, i'm not sure.

 

[robnissen]

sidenote: i thought some of the spots of light we see at night are galaxies... maybe not, i'm not sure.

There are a few messier objects visible without a telescope that are galaxies. But that handful of distant galaxies wouldn't add much to the night sky. And yes, it would be possible to use those for navigation, but that would not be "stellar" navigation, because they are galaxies and not stars.

 

[James_Hawk_III]

What's between galaxies?

Starbucks. Lots and lots of Starbucks.

 

[Delphinus100]

In regards to a comet being ejected, is there an escape velocity from the galaxy? Similar to an escape velocity from other gravity wells.

I remember one of the old, large-format Time-Life science books saying that escape velocity of this galaxy was about 300,000 mph.

Not that you would actually leave it in a hurry, even at twice that speed, only that it would be inevitable, barring any collisions or gravitational interactions with anything else...

 

[Mechulus]

Phlogiston.

 

[gholtorf]

Given that our understanding of what's IN the galaxies has become kind of uncertain given recent discovery. Asking what's between galaxies seems to have similar problems being understood. Both understanding problems combine in asking about Galactic Escape Velocity.
I'll bet it's more than we think it is. What's the escape velocity of "dark" anyway, or maybe "dark" sucks a little... maybe both? :?

 

[Basketvector]

sidenote: i thought some of the spots of light we see at night are galaxies... maybe not, i'm not sure.

Nothing you can see is a galaxy, just stars within the Milky Way (only close stars too, within 100 LY mainly). Supposedly Andromeda and Magellanic clouds are visible with the naked eye, but I call BS. Maybe if you're in the middle of the Pacific in the bloody 19th century you could see it. Has anyone actually seen Andromeda? I read recently that it's the same angular diameter as the full moon, which is just nuts.

 

[BigBangBong]

As far as I know between galaxies there is lots and lots of plasma in dark mode (or ionized gas aka dark matter as some call it).

But that's just me...

:twisted:

 

[junkheap]

I've seen Andromeda with a pair of binoculars. It's not easy to miss if you know where to look and you're not in an area with a lot of light pollution.

 

[MeteorWayne]

sidenote: i thought some of the spots of light we see at night are galaxies... maybe not, i'm not sure.

Nothing you can see is a galaxy, just stars within the Milky Way (only close stars too, within 100 LY mainly). Supposedly Andromeda and Magellanic clouds are visible with the naked eye, but I call BS. Maybe if you're in the middle of the Pacific in the bloody 19th century you could see it. Has anyone actually seen Andromeda? I read recently that it's the same angular diameter as the full moon, which is just nuts.

Yes, the Andromeda galaxy is visible to the unaided eye on clear nights even here in the moderately light polluted areas of New Jersey. Don't call it BS unless you've tried, and know where to look.

 

[Floridian]

Maybe if there were enough space between galaxies there could be some pretty large pockets of interstellar gas with some star systems.

Also, maybe a few anti-matter gas stations for inter-galactic travelers.