In article ,
says...

On 08/06/2017 20:26, Phillip Helbig (undress to reply) wrote:
In as much as galaxy and star planetary system size distributions
are different, are two different formation temperatures required
within the concept of Jeans' length?

The Jeans length is important for star formation, but the stuff which
forms (rocky) planets is only a small fraction of a larger cloud which
collapsed (as described by Jeans) to form a star. There doesn't seem to
be a lower limit on the size of "planets". There is an obvious upper
limit for (gaseous) planets---stars. The sizes of planets are
determined more by accretion, where gravitation is only one factor.

That suggests an interesting question.

Is it possible to compute either by simulation or from observations what
percentage of ordinary matter is tightly bound together (either
gravitationally or electromagnetically) as a function of length scale
(or mass).

There is clearly everything from ionised hydrogen, neutral hydrogen
(which must be a fair chunk in itself) dust grains and upto ~300Msun.
Does it obey some power law or are the preferred mass/length scales?

I would imagine that there has been a lot of work done in this area in
conjunction with studies of dark matter. Obviously the density and
distribution of baryonic dark matter (i.e. ordinary matter that's not in
stars) is a basic starting point for this research.

In fact, googling 'baryonic dark matter distribution' gives links which
will probably be in the ballpark of what you are interested in.

- Gerry Quinn

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