AST 115 1st Edition Lecture 13 Outline of Last Lecture I. Properties of the Planets of the Solar Systema. Diameterb. Massc. Average DensityII. The Terrestrial PlanetsIII. The Jovian PlanetsIV. Terrestrial vs Jovian Planetsa. Average Densityb. Moons/Satellitesc. Ringsd. Atmospheree. Rotation rateOutline of Current Lecture I. Regulatories of the Solar Systema. Characteristics of the 8 major planetsb. Terrestrial and Jovian planetsII. Age of the Solar SystemIII. Building Materials for the Solar Systema. Basic “ingredients”IV. Solar Nebula Theory and the “Nice Model”Current Lecture Regulatories of the Solar Systemo The orbits of the 8 major planets are:- Nearly in the same plane (ecliptic)- In the same direction- Nearly circular (they are ellipses, but somewhat circular)- Regularly spaced (NOT equally spaced)o Pluto is not in the same plane as the rest of the 8 major planets, this is why it wasre-classified as a Dwarf Planet.o Also, all the planets except Venus and Uranus rotate in the same direction as the Earth (they spin backwards)- We think Uranus was struck by an object causing it to rotate backwards.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- We don’t know why Venus spins backwards.o The two distinct types of planets are: Terrestrial and Jovian Age of the Solar Systemo Radioactive dating of rock samples from the Earth, Moon, and meteorites- 4.6 billion years ago- The theory for the formation of the Sun dates back to about this same time. Building Materials for the Solar SystemoAverage Density=MassVolumeo Basic Ingredients for making solar system objects:__Type__ __Average Density__1) “Metals” 10 g/cm3 [iron, Nickel]2) “Rocks” 3 g/cm3 [Silicates mixed with Magnesium, sulfur…]3) “Gases” ˂ 1 g/cm3 [H, He]4) “Ices” 1 g/cm3 [H2O = water, C O2 = Carbon Dioxide, NH3 = ammonia, CH4 = methane ] o Mixtures of different proportions of these building materials can match the observed average densities of objects.o Based on evidence, astronomers have devised explanations of the origin and development of the solar system. Solar Nebula Theory and the “Nice” Modelo The universe began in an extremely hot and dense state about 14 billion years ago.o After a few minutes, the temperature had dropped low enough for matter to form from energy.o Essentially, only Hydrogen and Helium were produced.o About 9 billion years later, the Sun and the planets formed, at about the same time, from material in an interstellar cloud.o Small amounts of “heavier” elements must have been present from past supernova explosions (produced in the cores of stars).o After being compressed, probably by another nearby supernova explosion, the solar nebula began gravitational contraction.o The spinning nebula flattened into a disk with a central concentration, the protosun.o Gravitational contraction of the protosun released energy to heat it to a temperature (about 10 million degrees K) at which it fuses.o Meanwhile, the gas, ice, and dust in the disk slowly accreted to produce the planets.- Accretion is the gradual clumping of small particles to make ever-larger ones.o Details of this process have emerged from supercomputer simulations. These are found in to the so-called Nice Model (pronounced “niece”).o The inner part of the disk was warmed by radiation from the protosun, no gases or ices left.o Only rocky and metallic particles were left behind.o Beyond the so-called snow (or frost) line, gases and icy particles were also
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