Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Jørgen Nilsson on 01/12/2011 16:30:04
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Jorgen Nilsson asked the Naked Scientists:
Thank you very much for the work all of you put into the podcasts (http://www.thenakedscientists.com/HTML/podcasts/), which I listen to with great delight and learn a lot. Thanks.
I have a question, with regards to the development of galaxies. As I understand it, galaxies and solar systems both develop in much the same way, and are subject to the same laws of physics.
Is it therefore possible, that galaxies as we know them from photos, are in the same development stage, as an early solar system. As time goes, the galaxies will sweep up the dust (in this case vast amounts of dust, stars and solar systems), and end up with a hugely massive center object, and circling this object, enormously huge planets. We would then end with a galaxy looking like a solar system, "only" a factor of 100.000.000 larger.
We would therefore happen to live in an era, where there has been enough time for the smaller solar systems to coagulate, and it would take ages before the galaxies coagulate.
Again many thanks for your shows (http://www.thenakedscientists.com/HTML/podcasts/),
Jorgen Nilsson
*Med venlig hilsen,*
*Jørgen Nilsson*
/personal details removed by mod. best not to publish those on an open site
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What do you think?
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Maybe? A galaxy should 'attract' gravitationally, but then you have the expansion to consider too, as it is accelerating it will mean (mainstream) that the distances between those galaxies gets larger. Waves are presumed to 'stretch' as they propagate between galaxies but I don't know what might happen to dust?
Maybe it gets 'pushed' aside in a expansion? Which then could show itself as distinct 'clouds', possibly? Or maybe the average density in the old patches of 'space' never change, and there is no 'up welling' effect to be seen?
It's very hard to imagine how this 'expansion' express itself in any (isolated) patch of space actually, and I may well be bicycling in the black younder here. It should also depend on the density of the galaxy. How many stars and how close they are together.
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I would guess that both galaxies and solar systems develop along similar lines (as you say) but on hugely different size and time scales. One looks much like the other as the processes are similar and the laws of physics the same for both. The main factors I suppose being gravity and conservation of momentum.
There's a limit on how big a planet can be. If a massive object contains enough mass in the form of usable fuel it will self ignite as a star. If it is large enough, at the end of its life it could go supernova and end up as a neutron star or if massive enough a black hole. So although there are similarities between galaxies and solar systems, one is not just a larger version of the other. A galaxy can create and re-cycle stars and solar systems.
It was speculated in the past that there were seen to be similarities between galaxies, solar systems and the structure of an atom.
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Jorgen the answer to your question is in some ways yes but in most ways no. The disc structure is a process for shedding angular momentum during the condensation of a cloud towards a condensed object. That's just about where the similarity ends.
The behaviour of material as it condenses under gravity is related to the energy produced and the amount of material small quantities produce planets medium quantities stars and large quantities black holes. All these are extremely small compared with the sixe of galaxies and almost never collide so this makes them behave very differently.
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I think there are a lot of similarities. But, perhaps a few differences too.
You could think of it as a fractal.
Stars orbiting Black Holes
Planets orbiting Stars
Moons orbiting Planets
Electrons orbiting Nuclei
etc.
Is there a mopping up of matter between the stars?
The Kuiper Belt and Oort Cloud is essentially material beyond the traditional boundaries of our solar system, but still controlled by the gravity of our sun and orbiting our sun. Are the Kuiper Plutoids still acreeting mass?
Depending on the stability of the interstellar relationships in the Milky Way, there are likely Lagrangian Clouds of small bodies in orbits between the stars.
Keep in mind that not all stars in the Milky Way are the same age, with HE1523 estimated at 13.2 billion years old. Our sun at 4.6 billion years old, and presumably some stars are currently being formed from supernovae remnants.
Small objects certainly collide with our sun and the larger planets all the time. Earth even undergoes regular meteor showers. However, stellar collisions seem to be relatively rare, unlike what would have been observed during the early solar system.