Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: JnA on 31/10/2010 08:02:17

Title: where is the symmetry in planets?
Post by: JnA on 31/10/2010 08:02:17

I have been doing some reading about the formation of the solar system and I have a, probably rookie, question..

why didn't the planets form in size in ascending (or descending) order? a shockwave is quite formatic I would think..

Title: where is the symmetry in planets?
Post by: Bored chemist on 31/10/2010 09:31:30

http://www.windsorfoodmachinery.com/manufacturers/formatic-(deighton)/43
What did you mean?

Title: where is the symmetry in planets?
Post by: Soul Surfer on 31/10/2010 11:26:23

There are two effects in governing the amount of material available for planetary formation from a discoidal cloud  of material surrounding the forming star.  The amount of volume that can be "swept" by the gravity of the forming planet and the amount of material in that volume  given a particular mass of growing planet the volume available is greater the further the planet is from the star. however the density of the cloud is probably getting less as you move away from the star.  So it seems logical that close in planets are likely to be smaller and further out ones bit larger up to a point and then eventually tail off as the material becomes sparse.

Other effects include the local temperature and the ability of the forming planet to hold on to light gasses in the initial flare of the star formation.  A star like the sun is very much brighter for a short period very early in its life before it settles down to a stable main sequence position and the Earth probably got a good frying which stripped all of its earlier atmosphere.  Jupiter and planets beyond probably avoided this fate.  If it hadn't the earth could have been the size of Uranus or Neptune if it had held on to all its gases when you consider the ratio of dense material to gases in the cloud.

It is also interesting to note that the formation of planets is an essential part of star formation because the planets trap the excess angular momentum in the cloud and allow the cloud to form a small object like a star without excessive rotation speeds disrupting it.

Title: where is the symmetry in planets?
Post by: imatfaal on 31/10/2010 14:53:01

Question is: what did Bored Chemist mean?  Or is there a spoofer in our ranks?

Title: where is the symmetry in planets?
Post by: RD on 31/10/2010 15:26:24

Quote from: JnA on 31/10/2010 08:02:17

why didn't the planets form in size in ascending (or descending) order?

They are in order of density ... http://en.wikipedia.org/wiki/Terrestrial_planet#Density_trends

Title: where is the symmetry in planets?
Post by: maffsolo on 31/10/2010 17:47:41

Quote from: imatfaal on 31/10/2010 14:53:01

Question is: what did Bored Chemist mean?  Or is there a spoofer in our ranks?

Along with material, position of the mass, matter accretion, and from the oven to the freezer, these masses in our solar system is also have to have been cooking, at different temperatures, over billions of years. This later factor is observed also.

Poor Pluto has been dismissed as a planet.
It also can be included here if you wish...

Quote from: RD on 31/10/2010 15:26:24

Quote from: JnA on 31/10/2010 08:02:17

why didn't the planets form in size in ascending (or descending) order?

They are in order of density ... http://en.wikipedia.org/wiki/Terrestrial_planet#Density_trends

Nasa being the source, this chart is sorted in the order of density.

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The density order does not match the order of distance from the Sun, Why?

http://www.smartconversion.com/otherInfo/Density_of_planets_and_the_Sun.aspx

Nasa  trumphs Wakiypedia, wikipedia scrambled my eggs to many times to depend on, as a source, to be the do all end all.

Title: where is the symmetry in planets?
Post by: JnA on 01/11/2010 01:58:37

So we have randomness out of pattern.

And, on further investigation I find out that the planets aren't necessarily in their original orbit when they were formed..  where were you people on planet migration?

:)

Thanks all.

Title: where is the symmetry in planets?
Post by: Bored chemist on 01/11/2010 07:08:02

I wondered what the word "formatic" meant.
All the references I could find led to that site or one like it.

Title: where is the symmetry in planets?
Post by: imatfaal on 01/11/2010 10:51:52

Aha - that explains matters; perhaps the reason I am not a professional scientist is that I had to read the sentence more than a couple of times before I noticed the word.