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Chapter 5 Book Notes

Chapter 5 Book Notes - Astronomy 180 Chapter 5 Formation of...

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Astronomy 180 Chapter 5: Formation of the Solar System and Other Planetary Systems (Pages 118-136) Solar system – the Sun, planets, their satellites, asteroids, comets, and related objects that orbit the Sun I. Formation of the Solar System: The solar system formed from a cloud of cold gas and dust Inconsistency: bodies in our solar system contain primarily heavy elements and extremely little hydrogen & helium Universe formed between 13 and 14 billion years ago ( Big Bang ) The solar system did not form as a direct result of the Big Bang Fusion – the process by which stars use various elements, such as hydrogen, helium, and carbon, to create energy; lighter elements are transformed into heavier ones. Fusion is considered a thermonuclear reaction because the heat generated deep in the cores of stars allows the elements to merge. Supernovae – bowl the stars apart as opposed to a gradual release of outer layers The solar system is believed to have formed from the debris left over from a previous generation of stars II. Formation of the Solar System: Gravity, rotation, and heat shaped the young solar system Solar nebula – The cloud of gas and dust from which the Sun and the rest of the solar system formed Originally the temperature was well below the freezing point of water and the nebula began with a diameter of at least 100 AU and a total mass 2-3 times that of the sun Protosun – The Sun prior to the time when hydrogen fusion began in its core The first heat in the solar system came from colliding gas, not nuclear fusion Rotation also played a key role in the formation of the solar system; the angular momentum (several swirling regions) prevented the entire nebula from collapsing into the protosun Protoplanetary disk ( proplyd ) – A disk of material encircling a protostar or a newborn star III. Formation of the Solar System: Collisions in the early solar system led to the formation of the planets The formation of the inner planets resulted from innumerable impacts of small, rocky particles in the protoplanetary disk Planetesimal – Primordial asteroidlike object from which the planets accreted Protoplanet – The embryonic stage of a planet when it is growing because of collisions with planetesimals Computer simulations of the inner solar system based on Newton’s laws suggest that accretion continued for over 100 million years & should lead to the formation of fewer than half a dozen planets Accretion
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