OSWAGO AST 311 - Chapter 8 Welcome to the Solar System

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Chapter 8 Welcome to the Solar System8.1 The Search for OriginsWhat properties of our solar system must a formation theory explain?What theory best explains the features of our solar system?Close Encounter HypothesisWhat have we learned?8.2 The Birth of the Solar SystemWhere did the solar system come from?Galactic RecyclingEvidence from Other Gas CloudsWhat caused the orderly patterns of motion in our solar system?PowerPoint PresentationConservation of Angular MomentumSlide 14FlatteningSlide 16Slide 17Slide 18Disks around Other StarsSlide 208.3 The Formation of PlanetsWhy are there two types of planet?Conservation of EnergySlide 24Slide 25How did terrestrial planets form?Slide 27Slide 28Accretion of PlanetesimalsHow did jovian planets form?Slide 31Slide 32What ended the era of planet formation?Slide 34Solar RotationSlide 36Slide 378.4 The Aftermath of Planet FormationWhere did asteroids and comets come from?Asteroids and CometsHow do we explain “exceptions to the rules”?Heavy BombardmentOrigin of Earth’s WaterCaptured MoonsHow do we explain the existence of Earth’s moon?Giant ImpactOdd RotationThought QuestionSlide 49Was our solar system destined to be?Thought Question Which of these facts is NOT explained by the nebular theory?Slide 52Slide 538.5 The Age of the Solar SystemHow does radioactivity reveal an object’s age?Radioactive DecaySlide 57Slide 58When did the planets form?Slide 60Chapter 8Welcome to the Solar System8.1 The Search for Origins•Our goals for learning•What properties of our solar system must a formation theory explain?•What theory best explains the features of our solar system?What properties of our solar system must a formation theory explain? 1. Patterns of motion of the large bodies •Orbit in same direction and plane2. Existence of two types of planets•Terrestrial and jovian3. Existence of smaller bodies•Asteroids and comets4. Notable exceptions to usual patterns•Rotation of Uranus, Earth’s moon, etc.What theory best explains the features of our solar system?•The nebular theory states that our solar system formed from the gravitational collapse of a giant interstellar gas cloud—the solar nebula(Nebula is the Latin word for cloud)•Kant and Laplace proposed the nebular hypothesis over two centuries ago•A large amount of evidence now supports this ideaClose Encounter Hypothesis•A rival idea proposed that the planets formed from debris torn off the Sun by a close encounter with another star.•That hypothesis could not explain observed motions and types of planets.What have we learned?•What properties of our solar system must a formation theory explain?–Motions of large bodies–Two types of planets–Asteroids and comets–Notable exceptions like Earth’s moon•What theory best explains the features of our solar system?–Nebular theory states that solar system formed from a large interstellar gas cloud.8.2 The Birth of the Solar System•Our goals for learning•Where did the solar system come from?•What caused the orderly patterns of motion in our solar system?Where did the solar system come from?Galactic Recycling•Elements that formed planets were made in stars and then recycled through interstellar spaceEvidence from Other Gas Clouds•We can see stars forming in other interstellar gas clouds, lending support to the nebular theoryWhat caused the orderly patterns of motion in our solar system?Conservation of Angular Momentum•Rotation speed of the cloud from which our solar system formed must have increased as the cloud contractedRotation of a contracting cloud speeds up for the same reason a skater speeds up as she pulls in her arms•Collisions between particles in the cloud caused it to flatten into a diskFlatteningCollisions between gas particles in cloud gradually reduce random motionsCollisions between gas particles also reduce up and down motionsSpinning cloud flattens as it shrinksDisks around Other Stars•Observations of disks around other stars support the nebular hypothesisWhat have we learned?•Where did the solar system come from?–Galactic recycling built the elements from which planets formed.–We can observe stars forming in other gas clouds.•What caused the orderly patterns of motion in our solar system?–Solar nebula spun faster as it contracted because of conservation of angular momentum–Collisions between gas particles then caused the nebula to flatten into a disk–We have observed such disks around newly forming stars8.3 The Formation of Planets•Our goals for learning•Why are there two types of planets?•How did terrestrial planets form?•How did jovian planets form?•What ended the era of planet formation?Why are there two types of planet?As gravity causes cloud to contract, it heats upConservation of EnergyInner parts of disk are hotter than outer parts.Rock can be solid at much higher temperatures than ice.Inside the frost line: Too hot for hydrogen compounds to form ices.Outside the frost line: Cold enough for ices to form.Fig 9.5How did terrestrial planets form?•Small particles of rock and metal were present inside the frost line•Planetesimals of rock and metal built up as these particles collided•Gravity eventually assembled these planetesimals into terrestrial planetsTiny solid particles stick to form planetesimals.Gravity draws planetesimals together to form planetsThis process of assembly is called accretionAccretion of Planetesimals•Many smaller objects collected into just a few large onesHow did jovian planets form?•Ice could also form small particles outside the frost line.•Larger planetesimals and planets were able to form.•Gravity of these larger planets was able to draw in surrounding H and He gases.Gravity of rock and ice in jovian planets draws in H and He gasesMoons of jovian planets form in miniature disksWhat ended the era of planet formation?Outflowing matter from the Sun -- the solar wind -- blew away the leftover gasesSolar Rotation•In nebular theory, young Sun was spinning much faster than now•Friction between solar magnetic field and solar nebular probably slowed the rotation over timeWhat have we learned?•Why are there two types of planets?–Only rock and metals condensed inside the frost line–Rock, metals, and ices condensed outside the frost line•How did the terrestrial planets form?–Rock and metals collected into planetsimals–Planetesimals then accreted into planets•How did the jovian planets form?–Additional ice


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OSWAGO AST 311 - Chapter 8 Welcome to the Solar System

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