Although they are, in cosmic terms, mere scraps—insignificant to the grand narrative of heavenly expansion—planets are the most diverse and intricate class of object in the universe. No other celestial bodies support such a complex interplay of astronomical, geologic, and chemical and biological processes. No other places in the cosmos could support life as we know it. The worlds of our solar system come in a tremendous variety, and even they hardly prepared us for the discoveries of the past decade, during which astronomers have found more than 200 planets.

The sheer diversity of these bodies’ masses, sizes, compositions and orbits challenges those of us trying to fathom their origins. When I was in graduate school in the 1970s, we tended to think of planet formation as a well-ordered, deterministic process—an assembly line that turns amorphous disks of gas and dust into copies of our solar system. Now we are realizing that the process is chaotic, with distinct outcomes for each system. The worlds that emerge are the survivors of a hurly-burly of competing mechanisms of creation and destruction. Many are blasted apart, fed into the fires of their system’s newborn star or ejected into interstellar space. Our own Earth may have long-lost siblings that wander through the lightless void.

6 Comments

1. 1. d4nnyb0y02 07:01 PM 5/13/08

   Rubbish.

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2. 2. Michael Woolfson 03:55 PM 6/1/08

   In the light of observational and theoretical constraints the Solar Nebula model is untenable. At almost every stage of the proposed mechanism there are difficulties either with formation timescales or with basic theoretical problems. As an example, at the distance of the Earth a planetary embryo of 0.1 Earth mass would plunge into the Sun in less than the time for the embryo to grow to terrestrial mass. This is due to what is called Type 1 migration. There are other and even more severe difficulties - detailed by those that work with the theory. For details read 'The Formation of the Solar System; Theories Old and New' by M M Woolfson. This also describes an alternative model without any presently-known theoretical or observational difficulties.

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3. 3. harlequinir 12:45 PM 10/30/08

   Many questions arise from this article.
   Where does the energy for heat transfer come from -during planet growth via collisions of all these particles can a planet really outshine its star? That's a lot of energy -it would need to be nuclear. Can the nuclear decay at the core of planets be explained with this evolution process?

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4. 4. Andira 11:52 PM 8/5/09

   Why should an increased gravity decrase the number of collisions by stirring up things? Is this correct according to standard gravitational theory, i.e. Einstein's

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5. 5. Andira 11:54 PM 8/5/09

   Why should an increased gravity decrase the number of collisions by stirring up things? Is this correct according to standard gravitational theory, i.e. Einstein's

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6. 6. angiras in reply to Michael Woolfson 03:54 PM 8/18/09

   See my blog on the Origin of thee Solar System:
   http://acksblog.firmament-chaos.com/2008/01/25/the-origin-of-the-solar-system/

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