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Chapter 19-3/19-4 Notes Astronomy Name: The Story of Planet Building Date: A. Planets formed from the same material as the ______________, still found in the sun’s atmosphere B. Rocky planet material formed from clumping together of __________ grains in the early cloud C. Mass of less than about 15 Earth masses: i. Planets can not grow by gravitational _______________ ii. _________________ planets D. Mass of more than about 15 Earth masses: i. Planets can _________ by gravitationally attracting material from the protostellar cloud. ii. _______________ planets (gas giants) Condensation of Solids A. Only condensed materials could stick together to form ___________________ B. Temperature in the protostellar cloud decreases __________________ C. Further out -> protostellar cloud _________________ -> metals with _____________ melting point condensed -> change of __________________ composition throughout solar system Formation and Growth of Planetesimals A. Planet formation starts with clumping together of grains of _______________ matter: Planetesimals B. Planetesimals (few cm to _________ in size) collide to form ______________. C. Planetesimal growth through _________________ (particles of about the same size gathering together) and ________________ (large particles attracting small particles). The Growth of Protoplanets A. Simplest form of planet growth i. As rocks melted, heavier elements sank to the center -> _____________________ ii. This also produces a secondary atmosphere -> ____________________ The Jovian Problem A. Two problems for the theory of planet formation: 1) observations of extrasolar planets indicate that ______________ planets are common 2) protoplanetary disks tend to be evaporated quickly (typically within about 100,000 years) by the ________________ of nearby massive stars a. Too _______________ for Jovian planets to grow! B. Solution: Computer simulations show that Jovian planets can grow by direct ____________ accretion without forming _______________ planetesimals. Explaining the Characteristics of the Solar System A. The Solar Nebula Hypothesis explains: 1) Disk shape and common sense of revolution: Inherited form the disk shape and rotation of the _______________________ 2) Division of Terrestrial/Jovian Planets: Result of decreasing __________________ throughout the Solar Nebula -> further out, ____________ elements condensed out to form heavier, _______________ planets 3) Icy Comets: Originating in the ______________ Cloud, very far away from the sun, in the coldest parts of the Solar Nebula Clearing the Nebula A. Remains of the early star nebula were cleared away by: i. radiation pressure of the ____________ ii. solar ____________ iii. Sweeping up of space debris by _________________ iv. ejection by close ___________________ with planets Extrasolar Planets A. Modern theory of planet formation is ______________________ i. Many stars should have ___________________ ii. Planets orbiting around other stars = “____________________ planets” iii. Extrasolar planets can not be imaged directly. iv. To detect: look for _________________ motion of the star around the common center of mass Indirect Detection of Extrasolar Planets A. Observing periodic ________________ shifts of stars with no visible companion B. Evidence for the wobbling motion of the star around the common center of mass of a ______________ system C. About __________ extrasolar planets detected so far using this method D. Indirect evidence through wobbling motion of stars detects primarily ____________ like, large planets Direct Detection of Extrasolar Planets A. Only in exceptional cases can extrasolar planets be observed directly i. Preferentially in the __________________. Planets may still be warm and emit infrared light; stars tend to be ____________ bright in the infrared than in the ______________.
