Planet Formation Having only one planetary system that we can carefully observe, we try to generalize from our solar system to model the formation of planets. This involves modeling the gravitational collapse of a large diffuse cloud of gas and dust. Given a non-zero angular momentum of the cloud with respect to some axis, there will be an increase in rotational angular velocity associated with the collapse. The formation of a disk perpendicular to the spin axis results, and in the case of our Sun we would call the growing system with its disk the primitive solar nebula. Modeling from the solar planets, it is judged that the protoplanetary disk must contain a minimum of about 2% of the system mass. In the protoplanetary disc, cooling leads to the condensation of some of the elements and compounds to dust grains, followed by the formation of larger solid bodies. Gravitational forces including tidal forces are involved. de Pater and Lissauer is a good reference for discussion of some of the stages of planet formation. Planetary disc about another star How do you form a habitable planet?

Index Solar System Illustration Solar System Concepts de Pater and Lissauer Chap 12

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A Planetary Disk This debris disc imaged by the Hubble Space Telescope surrounds the sun-like star called HD 107146, located 88 light-years away from Earth (image release Dec 9, 2004). This star is judged to be a yellow dwarf star similar to the Sun, though much younger (between 30 and 250 million years old). Two of NASA's Observatories, the Spitzer Space Telescope and the Hubble Space Telescope, have provided images of dusty planetary debris around stars the size of our sun. Spitzer has discovered for the first time dusty discs around mature, sun-like stars known to have planets. Hubble captured the most detailed image ever of a brighter disc circling a much younger sun-like star. The image is credited to NASA, ESA, C. Beichman (JPL), D. Ardila (JHU) and J. Krist (STScI/JPL) The detailed web reference is http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/33/

Index Solar System Illustration Solar System Concepts de Pater and Lissauer Chap 12

HyperPhysics********** Astrophysics R Nave

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