Why does a star with a planet with life need to be in a galaxy?

[Illustronic]

Is a galaxy necessary for the formulation of stars? Chicken/egg kind of analogy. Do stars only exist in galaxies? If so why, and how does that thought lend to the formation of galaxies to begin with?

This may seem to be such a rudimentary stupid question, but outside of the very core of a galactic 'black hole' why does a star need other nearby stars to afford a planet a 'Goldilocks' zone?

[jasonpatterson]

No, stars don't only exist in galaxies, they can be found in globular clusters in great quantity outside of galaxies (though these are still collections of stars.) I'm not sure whether we know of any, but it's hard to believe that there are not stars ejected from galaxies from time to time that wind up flying through intergalactic space.

The main reason that we expect life supporting planets to exist in galaxies is that the materials that go into making the living things wouldn't exist in sufficient quantity on a planet orbiting a star that had somehow formed between galaxies. In fact, such a planet would likely wind up being a gas planet. Our sun is thought to be a third generation star, that is, a star made at least partly from the remnants of a star that went supernova and was itself made at least partly from the remnants of a star that went supernova. It's conceivable that a second generation solar system could support life, but first generation is pretty much out of the question, as all that its biochemistry could be based on would be hydrogen with tiny quantities of other elements, nothing so heavy as carbon would be expected in any quantity.

The second reason we expect to find life in galaxies has to do with the Sutton effect. We expect to find stars with life in galaxies because that's where they keep the stars.

There are plenty of scifi stories that occur on planets/spaceships in intergalactic space. One good example was a response to Isaac Asimov's famous story Nightfall, the name and author of which I am sad to admit I have forgotten. (I could have sworn it was Robert Silverberg and that his story was also called Nightfall, but that appears to be wrong.)

ETA: Apparently stars in intergalactic space were found 15 years ago by the HST.

[Illustronic]

Yes shortly after I hit send I realized the extreme lack of matter in intergalactic space compared to galactic space so maybe the elements are not present or the vacuum and/or the lack of pressure would resist the formation of a real solar system to form out there much like water would not stay on a dead planet, sort of in a way.

Thanks for your response, I am just a layman with a pedestrian interest in the theory of everything.

[MattusMaximus]

To the thread title: it doesn't.

[Dinwar]

It's not inconcievable that a star system would get ejected during a collision between galaxies. If the system stayed together, and if the system had life (big ifs, but it's a big universe) there'd be life in intergalactic space.

That said, we're looking for a very small needle (though not as small as we previously thought) in a very large barn full of haystack. May as well look where we know we'll find hay. In other words, stars are concentrated in galaxies, so when looking for life we start by concentrating on where the most stars are.

[Dancing David]

Originally Posted by Illustronic

Yes shortly after I hit send I realized the extreme lack of matter in intergalactic space compared to galactic space so maybe the elements are not present or the vacuum and/or the lack of pressure would resist the formation of a real solar system to form out there much like water would not stay on a dead planet, sort of in a way.

Thanks for your response, I am just a layman with a pedestrian interest in the theory of everything.

Um there are lonely stars outside of galaxies.

http://apod.nasa.gov/apod/ap020119.html

[gnome]

Originally Posted by jasonpatterson

There are plenty of scifi stories that occur on planets/spaceships in intergalactic space. One good example was a response to Isaac Asimov's famous story Nightfall, the name and author of which I am sad to admit I have forgotten. (I could have sworn it was Robert Silverberg and that his story was also called Nightfall, but that appears to be wrong.)

There was a novelization of the Asimov short story "Nightfall" that was co-written by Asimov and Silverberg. Is that what you're thinking of, or was this another story yet?

[I Ratant]

"Nightfall" intrigued me.
I had to finger out where in the system the planet would be for the entire planet to go dark during one day's rotation.
Had to be the spring or autumnal equinox, otherwise an area at one pole or the other would not go dark that day.

[Bell]

Could a rogue planet support life?

[Dinwar]

Doubtful. There's very little in the way of energy (though there may be some), and it would eventually equilibrate thermally with the intergallactic dust and gas (ie, freeze solid at nearly absolute zero). It may hold on to some lithophiles or other extremophiles for some time, but it would eventually succumb to the Second Law of Thermodynamics.

[Bell]

Originally Posted by Dinwar

Doubtful. There's very little in the way of energy (though there may be some), and it would eventually equilibrate thermally with the intergallactic dust and gas (ie, freeze solid at nearly absolute zero). It may hold on to some lithophiles or other extremophiles for some time, but it would eventually succumb to the Second Law of Thermodynamics.

Thanks.

[gnome]

I suppose if it already had intelligent life before it went "rogue", it could support some "dome" habitats, as long as it had relatively efficient matter-energy conversion energy sources. It might take a while to consume a significant mass of the planet.

[Dinwar]

The problem isn't mass, it's useful mass. You're going to get energy from three sources in a rogue planet: geothermal, nuclear, or fossil fuel (trapped solar, essentially). Fossil fuels will run out quickly--remember, there is no sunlight, and therefore ALL work will require artificial light. Starlight can give you some light, but not between galaxies. Nuclear is probably the best bet, as most fissiable material would be at the surface and it's fairly efficient, but even then you're talking what, a few hundred years? Maybe, with conservation, a few thousand? Geothermal is perhaps the best bet, as it'll provide a few million years' worth of power (assuming a planet with active tectonics like Earth; I make this assumption because active tectonics has been proposed as something necessary for the formation of life; it's an open question as to whether the tectonic activity would continue as long as life did, though). But there you're talking about huge systems in a few locations, all of which are prone to destruction due to the same energy that you're extracting. Regions with shallow magma are typically NOT calm places. And bear in mind that the destruction of any energy generating station puts life as a whole on that planet at great risk of destruction. It's not impossible, but it's completely unfeasable with today's tech; the tech would probably be unique to the few rogue planets that harbor life, if it existed at all.

[I Ratant]

Get "The 12th Planet" by Zechariah Sitchin to see how a planet can spend thousands of years outside the habitable zone of a star, and support life as we know it.
It's a tossup as to which is worse; the cosmology (sucks big time) or the archeology (also a major suck).

[Roboramma]

Originally Posted by Dinwar

The problem isn't mass, it's useful mass. You're going to get energy from three sources in a rogue planet: geothermal, nuclear, or fossil fuel (trapped solar, essentially). Fossil fuels will run out quickly--remember, there is no sunlight, and therefore ALL work will require artificial light. Starlight can give you some light, but not between galaxies. Nuclear is probably the best bet, as most fissiable material would be at the surface and it's fairly efficient, but even then you're talking what, a few hundred years? Maybe, with conservation, a few thousand? Geothermal is perhaps the best bet, as it'll provide a few million years' worth of power (assuming a planet with active tectonics like Earth; I make this assumption because active tectonics has been proposed as something necessary for the formation of life; it's an open question as to whether the tectonic activity would continue as long as life did, though). But there you're talking about huge systems in a few locations, all of which are prone to destruction due to the same energy that you're extracting. Regions with shallow magma are typically NOT calm places. And bear in mind that the destruction of any energy generating station puts life as a whole on that planet at great risk of destruction. It's not impossible, but it's completely unfeasable with today's tech; the tech would probably be unique to the few rogue planets that harbor life, if it existed at all.

You have forgotten about fusion. I think you've also significantly underestimated the potential of fission.

[MattusMaximus]

Originally Posted by I Ratant

"Nightfall" intrigued me.
I had to finger out where in the system the planet would be for the entire planet to go dark during one day's rotation.
Had to be the spring or autumnal equinox, otherwise an area at one pole or the other would not go dark that day.

Not if the planet were eclipsed. Ever seen "Pitch Black"?

[MattusMaximus]

Originally Posted by gnome

I suppose if it already had intelligent life before it went "rogue", it could support some "dome" habitats, as long as it had relatively efficient matter-energy conversion energy sources. It might take a while to consume a significant mass of the planet.

Why would this be necessary when the parent star could easily have many billions of more years before burning out?

ETA: Sorry, I missed Bell's comment about a rogue planet.

[I Ratant]

Originally Posted by MattusMaximus

Not if the planet were eclipsed. Ever seen "Pitch Black"?

.
Never heard of it.
.
In "Nightfall" the occluding object is large enough that as it passes between the planet and the sole sun on one side, it is large enough to create the eclipse on the whole planet over the course of a day.
There's 4 suns on the other side of the planet's orbit that light that side, regardless of the eclipse, and the planet's primary is also on the multi-sun side.
The axial tilt that creates seasons would need be negated so the the side of the planet in the eclipse gets equally dark, pole to pole.

[MG1962]

Originally Posted by I Ratant

.
Never heard of it.
.
In "Nightfall" the occluding object is large enough that as it passes between the planet and the sole sun on one side, it is large enough to create the eclipse on the whole planet over the course of a day.
There's 4 suns on the other side of the planet's orbit that light that side, regardless of the eclipse, and the planet's primary is also on the multi-sun side.
The axial tilt that creates seasons would need be negated so the the side of the planet in the eclipse gets equally dark, pole to pole.

Asimov wasn't really shooting for that level of detail. The astronomy side of the story is actually a parody. Coments such as, not being able to establish laws of planetary motion when there is only one star in the system are side swipes at the notion planets could't form in binary system.

That being said, the environment that Asimov set his story is impossible for planetary formation, however they did not know that at the time of writing

[Illustronic]

Originally Posted by Dinwar

It's not inconcievable that a star system would get ejected during a collision between galaxies. If the system stayed together, and if the system had life (big ifs, but it's a big universe) there'd be life in intergalactic space.

That said, we're looking for a very small needle (though not as small as we previously thought) in a very large barn full of haystack. May as well look where we know we'll find hay. In other words, stars are concentrated in galaxies, so when looking for life we start by concentrating on where the most stars are.

I wasn't implying discovery of such a solar system, I was wondering if a galactic neighborhood was necessary to hold a solar system together. We are just now getting some actual data from the heliopause today. How much influence does nearby stars, not too close and not too far away actually sustain a habitable solar system is the core of the question.

Would the vacuum of intergalactic space disperse the energy of the star to the degree that a system is simply impossible. Are solar systems self contained or do they require a 'neighborhood'?

Thanks.

[wollery]

I don't see why a solar system should require any nearby stars to maintain a habitable planet. I don't know what you think the heliopause is, or does, but the main requirement for life as we know it is liquid water, which means that a habitable planet needs to be within a certain range of distance from its parent star.

[Dinwar]

Quote:

You have forgotten about fusion. I think you've also significantly underestimated the potential of fission.

Didn't forget about it--we don't currently HAVE viable fusion generators, so I can't comment on them. And as for fission, it'd work great--until we ran out. Which is the major problem. We're talking geologic time scales here, and once we're out of the solar system we're running on that and fossil fuels essentially (until we concentrate on something else). We'll burn through nuclear fuel at a pretty good rate, I'd imagine; even with refinement of spent fuel rods we've got a finite supply.

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Would the vacuum of intergalactic space disperse the energy of the star to the degree that a system is simply impossible. Are solar systems self contained or do they require a 'neighborhood'?

Self-contained. I once heard the density of stars in the Milky Way described as equivalent of a softball in New York City, a softball in LA, and a softball in Anckorage (may be misremembering that, but it's still an unimaginably long distance). A probe has reached the heliopause. It's not a significant percentage of the way to the nearest star, however. At this density they may as well be isolated, as far as life is concerned (the exception being that there's more chances of wiping out life when stars are close together).

[I Ratant]

Originally Posted by MG1962

Asimov wasn't really shooting for that level of detail. The astronomy side of the story is actually a parody. Coments such as, not being able to establish laws of planetary motion when there is only one star in the system are side swipes at the notion planets could't form in binary system.

That being said, the environment that Asimov set his story is impossible for planetary formation, however they did not know that at the time of writing

.
I wondered about that whole thing being in a globular cluster, without any of the other thousands of stars in those things being visible except for the period of the eclipse.
But it was the sudden viewing of all of them on the eclipsed side of the planet that destroyed the cultures at 1000 year intervals.
And the occulting planet had to be a humongous thing, for its umbra to keep the inhabited planet eclipsed for at least an entire rotation.
ISTR the book went deeper into the physics than the original story.
Just something I had to clear up for myself.

[jasonpatterson]

Originally Posted by gnome

There was a novelization of the Asimov short story "Nightfall" that was co-written by Asimov and Silverberg. Is that what you're thinking of, or was this another story yet?

It wasn't that. This was a response on the Xth anniversary of the story that told the story of a world in intergalactic space in the same sort of situation. I can't remember what their big event was, something like a tidelocked planet that experienced an eclipse, but their sky was virtual blackness. It was interesting in any case, but apparently didn't make enough of an impression on me to remember the title or author or where I read it or anything else.

[CapelDodger]

Originally Posted by Illustronic

I wasn't implying discovery of such a solar system, I was wondering if a galactic neighborhood was necessary to hold a solar system together. We are just now getting some actual data from the heliopause today. How much influence does nearby stars, not too close and not too far away actually sustain a habitable solar system is the core of the question.

Would the vacuum of intergalactic space disperse the energy of the star to the degree that a system is simply impossible. Are solar systems self contained or do they require a 'neighborhood'?

Thanks.

In comparison to the influence of the Sun, inter-stellar vacuum is as absolute as inter-galactic, energetically and gravitationally. The Solar System might as well be a completely isolated system surrounded by an infinite energy sink, inside or outside a galaxy. The Sun doesn't just rule the neighbourhood, it defines it.

Could the matter required to form something like the Solar Sytem come together and coalesce by chance in inter-galactic space? A negligible probability. Zip. Nada. Won't happen. But in theory could.

[MG1962]

Originally Posted by CapelDodger

In comparison to the influence of the Sun, inter-stellar vacuum is as absolute as inter-galactic, energetically and gravitationally. The Solar System might as well be a completely isolated system surrounded by an infinite energy sink, inside or outside a galaxy. The Sun doesn't just rule the neighbourhood, it defines it.

Could the matter required to form something like the Solar Sytem come together and coalesce by chance in inter-galactic space? A negligible probability. Zip. Nada. Won't happen. But in theory could.

So where do globular clusters come from?

[Dinwar]

Isn't that one of the great unanswered questions in astronomy?

[Damien Evans]

Originally Posted by MG1962

So where do globular clusters come from?

I don't know about the rest, but it's theorised in Omega Centauri's case that it's the remaining nucleus of a galaxy long since eaten up by the Milky Way.

http://en.wikipedia.org/wiki/Omega_Centauri

[MG1962]

Originally Posted by Dinwar

Isn't that one of the great unanswered questions in astronomy?

True, in the same way there is a fair body of evidence that many such clusters did not form within a galactic environment

[MG1962]

Originally Posted by Damien Evans

I don't know about the rest, but it's theorised in Omega Centauri's case that it's the remaining nucleus of a galaxy long since eaten up by the Milky Way.

http://en.wikipedia.org/wiki/Omega_Centauri

Yeah M15 fits into the same class

[HansMustermann]

"Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." -- Douglas Adams, The Hitchhiker's Guide to the Galaxy

To put it into perspective, our galaxy alone is 100,000 light years in diameter. If you made a nice big picture of it, say, 2048x2048, it would be about 50 light years per pixel. Earth, Alpha Centauri, Sirius, and several dozens of other stars would be in the same pixel. That big.

We're currently not even looking for planets in galaxies, we're looking in exactly one galaxy, and mostly in our own immediate vicinity. And I don't even just mean "our corner" or "our quadrant", but really in that digital picture analogy, we're looking in and around the pixel we're in.

[I Ratant]

CSIanywhere) could enhance that pixel and find all kinds of things.

[LarianLeQuella]

Originally Posted by HansMustermann

To put it into perspective, our galaxy alone is 100,000 light years in diameter. If you made a nice big picture of it, say, 2048x2048, it would be about 50 light years per pixel. Earth, Alpha Centauri, Sirius, and several dozens of other stars would be in the same pixel. That big.

Nommed.

[Illustronic]

Our star is said to be a third generation star, the kind that could form a habitable zone of planets, from nebulas of exploded stars that created heavy elements crucial to life, oxygen, carbon, iron. I would find that too sparse in intergalactic space to be concentrated into forming a star such as our sun. I'm not saying only red giants exist between galaxies, or ejected systems somehow thousands of light years away from galaxies, but it doesn't make sense to me that the elements could bind out there.

I know our methods of detection are not sensitive enough to know, but in theory, is there enough matter stuff out there or is the nebulous galaxies the only womb possible. Forget about water, H is the most, and eager to bind O are nearly together the two most common elements in the Universe, makes perfect mathematical sense that where there is the condition/temperature, water is an unavoidable inevitability. But a planet needs an atmosphere to keep it, an iron core.

[Illustronic]

Just one other point, how important is our unusually large moon involved in keeping our planet tectonically alive? We don't see that outside of Pluto yet, but hence, Pluto is not a planet anymore...ha heh.

Earth is rare, we may never see anything like it ever. Too many 'coincidental workers' on our side, Jupiter, even Saturn and the Asteroid belt. Seems we get all of the imaginable bodies in our one little insignificant system, along with the outer gas giants we have little idea how much they may be protecting our life from Oort cloud invaders.

NOTE: this is not turning into a 'religious' thread, thanks for the scientific input.

It just seems to me that all of our cards were dealt for us to compete for life from the start, and life is the inevitable outcome of our unique and rare solar system. Earth may be the only place its moon is such a size 400 times smaller than earth's star 400 times closer to create a total solar eclipse, viewed from the ground of earth. Haven't any of you ever wondered why? How? Is that to be expected to be a common occurrence? Let alone intergalactically.

[wollery]

Originally Posted by Illustronic

Our star is said to be a third generation star, the kind that could form a habitable zone of planets, from nebulas of exploded stars that created heavy elements crucial to life, oxygen, carbon, iron. I would find that too sparse in intergalactic space to be concentrated into forming a star such as our sun. I'm not saying only red giants exist between galaxies, or ejected systems somehow thousands of light years away from galaxies, but it doesn't make sense to me that the elements could bind out there.

The elements "bind" by gravity. As long as the molecular cloud from which a star must form is dense enough it will collapse under self-gravity. Remember, the galaxies are "out there".

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I know our methods of detection are not sensitive enough to know, but in theory, is there enough matter stuff out there or is the nebulous galaxies the only womb possible.

It isn't a matter of the amount of stuff (although you need at least (IIRC) 2 solar masses for a cloud to collapse against kinetic pressure) but how dense it is. You don't need a galaxy's worth of mass to form stars.

Quote:

Forget about water, H is the most, and eager to bind O are nearly together the two most common elements in the Universe, makes perfect mathematical sense that where there is the condition/temperature, water is an unavoidable inevitability. But a planet needs an atmosphere to keep it, an iron core.

Amongst many other things, although I'm not sure that an iron core is necessary.

[wollery]

Originally Posted by Illustronic

Just one other point, how important is our unusually large moon involved in keeping our planet tectonically alive? We don't see that outside of Pluto yet, but hence, Pluto is not a planet anymore...ha heh.

Nobody actually knows. The problem is that we're working with only one data point, so we can't do any statistical studies.

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Earth is rare, we may never see anything like it ever.

Too early to say how rare Earth-like planets are. We're looking for systems similar to ours, but our detection limits are too large at the moment to allow us to find such a system.

Quote:

Too many 'coincidental workers' on our side, Jupiter, even Saturn and the Asteroid belt. Seems we get all of the imaginable bodies in our one little insignificant system, along with the outer gas giants we have little idea how much they may be protecting our life from Oort cloud invaders.

And such collections of "imaginable bodies" may be pretty common. We have no idea yet.

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NOTE: this is not turning into a 'religious' thread, thanks for the scientific input.

No problem.

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It just seems to me that all of our cards were dealt for us to compete for life from the start, and life is the inevitable outcome of our unique and rare solar system.

Again, we have no idea how rare such systems are.

Quote:

Earth may be the only place its moon is such a size 400 times smaller than earth's star 400 times closer to create a total solar eclipse, viewed from the ground of earth. Haven't any of you ever wondered why? How? Is that to be expected to be a common occurrence? Let alone intergalactically.

Coincidence. A few million years ago it was closer to the Earth and total eclipses lasted longer. Today not all eclipses are total, some are annular, because the Earth-Moon distance varies as the Moon orbits the Earth, and the Sun-Earth distance varies as the Earth orbits the Sun. When the Moon is at apogee and the Earth at perihelion the Moon isn't large enough, relatively, to cover the entire Sun. Another million years or so and the Moon will never be able to completely cover the Sun.

[Illustronic]

Nice wollery, and also thanks, but it took us over 3 billion years to see our moon eclipse our sun. I'm not in the position right now to go into much more depth about your replies.

But briefly:
Iron is as essential to life as we know it as carbon and oxygen, its my blood. There are a lot of lifeless hydrogen suns out there, biologically we can't imagine life to sustain the physical size without carbon, silicone will not support our DNA strand by itself with say, methane and ammonia.

From what minute knowledge I'm aware of where I work from chemists, stability is not sufficient to create large enough (I'll paraphrase for my lack of study in this field), is not efficient enough to support the bodies we know on Earth, the living ones that can adapt to changing environment.

If a molecular cloud could be dense enough in intergalactic space you might have a point on that one, it's pretty sparse and cold out there. Have we even seen a nebula intergalactically yet?

The rest is supposition. The brief time you spent to dissect every though I have is appreciated (don't get me wrong), I just thing some of it is coming out of your ass, no offense.

[steve s]

Originally Posted by Illustronic

Just one other point, how important is our unusually large moon involved in keeping our planet tectonically alive?

Pretty much zilch.
http://en.wikipedia.org/wiki/Geother...t#Heat_sources

Quote:

Earth is rare, we may never see anything like it ever. Too many 'coincidental workers' on our side, Jupiter, even Saturn and the Asteroid belt. Seems we get all of the imaginable bodies in our one little insignificant system, along with the outer gas giants we have little idea how much they may be protecting our life from Oort cloud invaders.

You would expect life to arise on a planet that is conducive towards life. You're not going to expect to find life, or at least not advanced life, on a planet that is inhospitable toward life. It only seems like a coincidence to us because we are here to experience this planet. If the earth had been drastically different, then we would have adapted to that environment or we wouldn't have evolved at all.

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Earth may be the only place its moon is such a size 400 times smaller than earth's star 400 times closer to create a total solar eclipse, viewed from the ground of earth. Haven't any of you ever wondered why? How?

The moon's orbit around the earth is an ellipse, which means that the distance from the earth to the moon varies. This means that the apparent size of the moon as seen from earth also varies. Sometimes the moon appears smaller than the sun and you get an annular eclipse. Sometime it appears larger and completely blocks out the sun. If the moon happens to be in just the right place in its orbit during an eclipse, it will appear the same size as the sun.

Also, the moon is gradually moving away from earth so there will come a day when total eclipses will no longer occur.

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Is that to be expected to be a common occurrence? Let alone intergalactically.

Common? No. But when you consider there must be at least a sextillion stars in the universe, it must occur occasionally.

Steve S

[wollery]

Originally Posted by Illustronic

Nice wollery, and also thanks, but it took us over 3 billion years to see our moon eclipse our sun.

Like I said, coincidence.

Quote:

But briefly:
Iron is as essential to life as we know it as carbon and oxygen, its my blood. There are a lot of lifeless hydrogen suns out there, biologically we can't imagine life to sustain the physical size without carbon, silicone will not support our DNA strand by itself with say, methane and ammonia.

I never said iron wasn't essential to life, I questioned the necessity of an iron core for a life bearing planet.

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From what minute knowledge I'm aware of where I work from chemists, stability is not sufficient to create large enough (I'll paraphrase for my lack of study in this field), is not efficient enough to support the bodies we know on Earth, the living ones that can adapt to changing environment.

I have absolutely no idea what part of my posts this is in response to.

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If a molecular cloud could be dense enough in intergalactic space you might have a point on that one, it's pretty sparse and cold out there. Have we even seen a nebula intergalactically yet?

They'd be pretty hard to see if they were small enough to only produce one or two stars, in point of fact, one or two average sized stars on their own in intergalactic space would be pretty much impossible to see. We have difficulty picking out solar type stars at about a kiloparsec, and that's well within the Galaxy.

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The rest is supposition. The brief time you spent to dissect every though I have is appreciated (don't get me wrong), I just thing some of it is coming out of your ass, no offense.

Some of it is guesswork - like I said, we don't have statistics for a lot of this stuff, but a lot is based on my knowledge of star formation, stellar dynamics, stellar evolution and stellar populations that I've picked up over the years working as a professional astronomer.