Formation of the Solar System and Other Planetary SystemsQuestions to Ponder about Solar SystemQuestions to Ponder about OriginsThere are two broad categories of planets: Earthlike (terrestrial) and Jupiterlike (jovian)DensityThe Terrestrial PlanetsJovian Planets are the outer planets (except for Pluto)Pluto (dwarf planet) - Not terrestrial nor JovianSeven largest moons are almost as big as the terrestrial planetsSpectroscopy reveals the chemical composition of the planetsPhases and Phase Diagram (Not in text but important)Slide Number 12Slide Number 13Hydrogen and helium are abundant on the Jovian planets, whereas the terrestrial planets are composed mostly of heavier elementsAsteroids (rocky) and comets (icy) also orbit the SunCratering on Planets and SatellitesA planet with a magnetic field indicates an interior in motionSlide Number 18Comparing Terrestrial and Jovian PlanetsAny model of solar system origins must explain the present-day Sun and planetsThe abundances of the chemical elements are the result of cosmic processesAll heavy elements (>Li) were manufactured by stars after the origin of the universe itself, either by fusion deep in stellar interiors or by stellar explosions.Slide Number 23The abundances of radioactive elements reveal the solar system’s ageThoughtful InterludeSolar System Origins QuestionsOrigin of Universe Preview (a la Big Bang) (will re-visit at end of semester)Abundance of the Chemical ElementsLogarithmic Plot of AbundanceA Linear View of AbundanceRecall ObservationsPlanetary SummaryOther Planet ObservationsSome ConclusionsNebular Condensation (protoplanet) ModelNebular Condensation PhysicsNebular Condensation ChemistryNebular Condensation SummaryA Pictorial View of Solar System OriginsPictorial View ContinuedHST Pictorial Evidence of Extrasolar System FormationHST Pictorial Evidence of Extrasolar System FormationThe Sun and planets formed from a solar nebula Slide Number 44Slide Number 45Slide Number 46Slide Number 47Slide Number 48The planets formed by the accretion of planetesimals and the accumulation of gases in the solar nebulaChondrulesSlide Number 51Slide Number 52Slide Number 53Astronomers have discovered planets orbiting other starsFinding Extrasolar PlanetsExtrasolar PlanetsAstronomical Jargon1Formation of the Solar System and Other Planetary Systems2Questions to Ponder about Solar System1. Are all the other planets similar to Earth, or are they very different?2. Do other planets have moons like Earth’s Moon?3. How do astronomers know what the other planets are made of?4. Are all the planets made of basically the same material?5. What is the difference between an asteroid and a comet?6. Why are craters common on the Moon but rare on the Earth?7. Why do interplanetary spacecraft carry devices for measuring magnetic fields?8. Do all the planets have a common origin?3Questions to Ponder about Origins1. What must be included in a viable theory of the origin of the solar system?2. Why are some elements (like gold) quite rare, while others (like carbon) are more common?3. How do we know the age of the solar system?4. How do astronomers think the solar system formed?5. Did all of the planets form in the same way?6. Are there planets orbiting other stars? How do astronomers search for other planets?4There are two broad categories of planets: Earthlike (terrestrial) and Jupiterlike (jovian)• All of the planets orbit the Sun in the same direction and in almost the same plane• Most of the planets have nearly circular orbits5DensityVmD • The average density of any substance depends in part on its composition • An object sinks in a fluid if its average density is greater than that of the fluid, but rises if its average density is less than that of the fluid • The terrestrial (Earth-like) planets are made of rocky materials and have dense iron cores, which gives these planets high average densities• The Jovian (Jupiter-like) planets are composed primarily of light elements such as hydrogen and helium, which gives these planets low average densities6The Terrestrial Planets• The four innermost planets are called terrestrial planets– Relatively small (with diameters of 5000 to 13,000 km)– High average densities (4000 to 5500 kg/m3)– Composed primarily of rocky materials7Jovian Planets are the outer planets (except for Pluto)• Jupiter, Saturn, Uranus and Neptune are Jovian planets– Large diameters (50,000 to 143,000 km)– Low average densities (700 to 1700 kg/m3)– Composed primarily of hydrogen and helium.The Jovian Planets8Pluto (dwarf planet) - Not terrestrial nor Jovian•Pluto is a special case– Smaller than any of the terrestrial planets– Intermediate average density of about 1900 kg/m3– Density suggests it is composed of a mixture of ice and rock9• Some (3) comparable in size to the planet Mercury (2 are larger)• The remaining moons of the solar system are much smaller than theseSeven largest moons are almost as big as the terrestrial planets10Spectroscopy reveals the chemical composition of the planets• The spectrum of a planet or satellite with an atmosphere reveals the atmosphere’s composition• If there is no atmosphere, the spectrum indicates the composition of the surface.• The substances that make up the planets can be classified as gases, ices, or rock, depending on the temperatures and pressures at which they solidify• The terrestrial planets are composed primarily of rocky materials, whereas the Jovian planets are composed largely of gas11Phases and Phase Diagram (Not in text but important)12Spectroscopy of Titan (moon of Saturn)13Spectroscopy of Europa (moon of Jupiter)14Hydrogen and helium are abundant on the Jovian planets, whereas the terrestrial planets are composed mostly of heavier elementsJupiterMars15Asteroids (rocky) and comets (icy) also orbit the Sun• Asteroids are small, rocky objects• Comets and Kuiper Belt Objects are made of “dirty ice”• All are remnants left over from the formation of the planets• The Kuiper belt extends far beyond the orbit of Pluto• Pluto (aka dwarf planet) can be thought of as a large member of the Kuiper Belt16Cratering on Planets and Satellites• Result of impacts from interplanetary debris– when an asteroid, comet, or meteoroid collides with the surface of a terrestrial planet or satellite, the result is an impact crater• Geologic activity renews the surface and erases craters– extensive cratering means an old surface and