3 comments on “Minutiae of Planetary Formation

  1. Is it so much that the dust form together at the center of the nebulae or could there be a greater concentration of gas and dust off to one side and stars/planets start to form there? Also, what is ice made of? Every time I read about it I keep visualizing water-ice but I know that can’t be correct.

    Anyways, I really like this post.

  2. Well, to look at it simply (the whole this way more complex than we have room for here), for the star itself, the central region is where material starts to collect — mostly the hydrogen gas, which is what the star is formed from. The dusty material is pushed along by various forces (radiation pressure, etc.) out into the nebula. The action of star birth sweeps the immediate environment of the star free from hydrogen, leaving behind the dust which can coagulate/accrete as I suggest in the main article. I imagine that this causes mass accretions and instabilities in the cloud that make it more likely for other bodies to form out of whatever’s available in that region — dust and larger “asteroid” type particles for rocky bodies, and in the outer regions you have gas and icy material and dust to form the outer worlds. In the outermost regions, you get the cometary stuff.

    The ices are not just water. In our own solar system, we see ices of methane, ammonia, carbon dioxide — stuff like that. It can exist in the icy form in the colder regions far from the Sun, so there’s no reason to think that wouldn’t happen elsewhere in other solar systems.

    Ice particles aren’t just little flakes of ice. Often enough they are bits of dust that have had ice crystals freeze around them (hailstones often form this way — with dust particles that get swept up by strong winds and then form hailstones at super high altitudes. (Google hail stones, you can find a wealth of info about how they form). In space, those little bits of ice make contact with each other in the nebula and begin sticking together as they do. Hence the growth of icy bodies. Rocky material coagualates too, but it takes a bit more force for that to happen. The pieces have to clunk together hard enough to stick together but not so hard they just break apart. That is a hot area of study right now.

  3. Pingback: ScienceBlogs Channel : Physical Science | BlogCABLE.COM

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