Chapter 8Stardate.orgSlide 3Slide 4Slide 5Slide 6The Solar SystemThe SunSlide 9The PlanetsSlide 11Slide 12Slide 13ErisCeresSlide 16Inner PlanetsOuter PlanetsDwarf PlanetsSatellitesAsteroids and CometsSlide 22Slide 23Slide 24Measuring CompositionMeasuring Composition: DensitySlide 27Analysis Concludes:Slide 29Age of the Solar SystemBode’s LawOrigin of the Solar SystemThe Solar Nebula HypothesisSlide 34Interstellar CloudsSlide 36In the Beginning…The Solar NebulaDisk ObservationsTemperatures in the Solar NebulaCondensationCondensation in the Solar NebulaFormation of PlanetsAccretionPlanetesimalsFormation of the PlanetsSlide 47Continuous BombardmentFormation of MoonsFinal StagesFormation of AtmospheresExosolar PlanetsSlide 53A Sample of ExoplanetsChapter 8Survey of Solar SystemsCopyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Stardate.orgIf you follow Harry Potter ……………………HNSKY captureHNSKY captureThe Solar System•The Solar System is occupied by a diversity of objects, but shows an underlying order in the dynamics of their movements•The planets form two main families: –solid rocky inner planets–gaseous/liquid outer planets•Astronomers deduce that the Solar System formed some 4.5 billion years ago out of the collapse of a huge cloud of gas and dustThe Sun•The Sun is a star, a ball of incandescent gas whose output is generated by nuclear reactions in its core•Composed mainly of hydrogen (71%) and helium (27%), it also contains traces of nearly all the other chemical elementsThe Sun•It is the most massive object in the Solar System – 700 times the mass of the rest of the Solar System combined•Its large mass provides the gravitational force to hold all the Solar System bodies in their orbital patterns around the SunThe Planets•Orbits are almost circular lying in nearly the same plane – Pluto is the exception with a high (17°) inclination of its orbitThe PlanetsThe Planets•All of the planets travel counterclockwise around the Sun (as seen from high above the Earth’s north pole)•Six planets rotate counterclockwise; Venus rotates clockwise (retrograde rotation), and Uranus appears to rotate on its sideEarthErisCeresThe PlanetsInner Planets•Mercury, Venus, Earth, Mars•Small rocky (mainly silicon and oxygen) bodies with relatively thin or no atmospheres•Also known as terrestrial planetsOuter Planets•Jupiter, Saturn, Uranus, and Neptune•Gaseous, liquid, or icy (H2O, CO2, CH4, NH3)•Also referred to as Jovian planets•Jovian planets are much larger than terrestrial planets and do not have a well-defined surfaceDwarf Planets•Pluto and similar objects fail to fit into either family•Recently, scientists have discovered more than 200 similar objects orbiting the Sun at the same distance as Pluto•In 2006, a new family was introduced – the dwarf planets–Massive enough to pull themselves spherical–Orbits have not been swept clear of debrisSatellites•The number of planetary satellites changes frequently as more are discovered!–Jupiter 63 –Saturn 60 –Uranus 27 –Neptune 13 –Mars 2 –Earth 1–Mercury and Venus are moonless–Even Pluto and Eris have moons!Asteroids and Comets•Composition and size–Asteroids are rocky or metallic bodies ranging in size from a few meters to 1000 km across (about 1/10 the Earth’s diameter)–Comets are icy bodies about 10 km or less across that can grow very long tails of gas and dust as they near the Sun and are vaporized by its heatAsteroids and Comets•Their location within Solar System–Most asteroids are in the asteroid belt between Mars and Jupiter indicating that these asteroids are the failed building-blocks of a planet–Some comets may also come from a disk-like swarm of icy objects that lies beyond Neptune and extends to perhaps 1000 AU, a region called the Kuiper Beltpronounced rhyming with "viperApophis (The 2036 Asteroid)Asteroids and CometsMost comets orbit the Sun far beyond Pluto in the Oort cloud, a spherical shell extending from 40,000 to 100,000 AU from the SunMeasuring Composition•Since the inner and outer planets differ dramatically in composition, it is important to understand how composition is determined•A planet’s reflection spectrum can reveal a planet’s atmospheric contents and the nature of surface rocks•Seismic activity has only been measured on Earth for the purposes of determining interior compositionMeasuring Composition: Density•A planet’s average density is determined by dividing a planet’s mass by its volume–Mass determined from Kepler’s modified third law–Volume derived from a planet’s measured radiusMeasuring Composition: Density•Once average density known, the following factors are taken into account to determine a planet’s interior composition and structure:–Densities of abundant, candidate materials–Variation of these densities as a result of compression due to gravity–Surface composition determined from reflection spectra–Material separation by density differentiation–Mathematical analysis of equatorial bulgesAnalysis Concludes:•The terrestrial planets, with average densities ranging from 3.9 to 5.5 g/cm3, are largely rock and iron, have iron cores, and have relative element ratios similar to the Sun except for deficiencies in lightweight gassesAnalysis Concludes:•The Jovian planets, with average densities ranging from 0.71 to 1.67 g/cm3, have relative element ratios similar to the Sun and have Earth-sized rocky coresAge of the Solar System•All objects in the Solar System seem to have formed at nearly the same time, out of the same original cloud of gas and dust•Radioactive dating of rocks from the Earth, Moon, and some asteroids suggests an age of about 4.5 billion yrs•A similar age is found for the Sun based on current observations and nuclear reaction ratesBode’s Law•First noted in 1766, formalized mathematically by J. E. Bode in 1778–0 3 6 12 24 48 96 192 384 –4 7 10 16 28 52 100 196 388 –0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6 38.8 •Does a pretty good job, up to a pointOrigin of the Solar System•A theory of the Solar System’s formation must account for the following:–Planets orbit in the same direction and in the same plane–Rocky inner planets and gaseous/liquid/icy outer planets–Compositional trends in the solar system–All Solar System bodies appear to be less than 4.5 billion years old–Other details – structure of