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Dec 6, 2023

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AST 101 Lab 10 Overall Structure of the Solar System Lab 10 Overall Structure of the Solar System PURPOSE This laboratory exercise will allow the student to explore the general characteristics of objects in the solar system and relate them to a theory of solar system formation. REFERENCES Exploring the Planets , Hamblin & Christiansen, 1990 BACKGROUND How did the solar system form? When did this happen? Why are the objects in the solar system arranged in the particular order we find them in? While it is indeed difficult to interpret events billions of years in the past from the evidence available to us today, it can be done. A combination of careful observations of present conditions and knowledge of physical principles allows us to reconstruct the history of the solar system. Observations of variables such as temperature or mass density are crucial to our understanding of how the solar system works. We will use these variables to build a storyline of the solar system’s formation and evolution. First we will examine the densities of objects and compare them to the densities of known materials. Then we will relate this to the temperature structure of the solar system. Finally, we will attempt to draw some basic conclusions about the solar system and its history. EQUIPMENT ruler PROCEDURE Exercise 1: The Mass Density Profile of the Solar System It is well established that different objects in the solar system are made from different materials. Is this due to random causes, or is there a reason for this? We will explore this issue by plotting the density of objects as a function of two different variables. Table 10-1 contains density data from selected objects in the solar system. Using this table, plot density as a function of distance from the Sun and plot density as a function of object diameter.
AST 101 Lab 10 Overall Structure of the Solar System Table 10-1: Density Gradient of the Solar System Object Distance from Sun (AU) Density (g/cc) Diameter (km) Mercury 0.387 5.44 4880 Venus 0.723 5.25 12,104 Earth 1.000 5.52 12,756 Moon 1.000 3.34 3476 Mars 1.524 3.93 6787 Jupiter 5.203 1.3 143,800 Io 5.203 3.50 3640 Europa 5.203 3.03 3130 Ganymede 5.203 1.93 5280 Callisto 5.203 1.79 4840 Saturn 9.54 0.69 120,660 Mimas 9.54 1.4 392 Enceladus 9.54 1.2 500 Tethys 9.54 1.2 1060 Titan 9.54 1.88 5150 Comet Halley 18 ~0.1 16 by 8 Uranus 19.18 1.28 51,120 Miranda 19.18 1.35 470 Ariel 19.18 1.66 1150 Oberon 19.18 1.58 1520 Neptune 30.07 1.64 49,560 Triton 30.07 2.01 2700 Pluto 39.44 2.06 2284 Charon 39.44 2.06 1192 Exercise #2: The Temperature Profile of the Solar System The fact that the temperature of objects in the solar system changes with distance from the Sun is obvious - objects closer to the Sun are hotter and objects further from the Sun are cooler. A more difficult question to ask is how the temperature of the original solar nebula behaved with increasing distance from the protosun. This is a more fundamental question, as it addresses why different objects are made of different materials in the solar system. Astronomers assume that the composition of the original nebular disk was the same as that of the present-day Sun. The Sun consists mostly of hydrogen and helium gas, but only the jovian planets have similar compositions. All other objects in the solar system are much smaller than jovian planets and are generally made up of various combinations of solid materials. Why are small objects not made of hydrogen and helium?
AST 101 Lab 10 Overall Structure of the Solar System To approach a solution, we must consider the temperature conditions of the early solar nebula. The central region that contained the protosun was extremely hot, as was the rest of the nebula. The nebula cooled from the outside-in, with objects condensing out of the nebula. The closer the protoplanets were to the protosun, the higher their temperatures; the further from the protosun, the lower their temperatures. Materials which condense at low temperatures could not do so close to the protosun, so they tend to be found relatively far from the Sun. Materials which condense at high temperatures could do so close to the protosun, so they tend to be found relatively close to the Sun. We will plot two graphs to examine this hypothesis. The condensation temperatures and densities of various materials are listed in Table 10-2, along with the distances from the protosun at which these materials could condense. First plot the density of the materials as a function of condensation temperature and then plot the condensation temperature as a function of distance from the Sun. Table 10-2: Physical Properties of Various Substances Condensation Condensation Substance Density (g/cc) Temperature (K) Distance (AU)* Iron-Nickel alloy 7.9 1470 0.36 Oxide minerals 3.2 1450 0.37 Feldspars 2.8 1000 0.61 Troilite 4.6 700 0.98 Carbonates 2.9 400 2.07 Water ice 0.92 273 3.44 Carbon Dioxide ice 1.56 216 4.70 Ammonia ice 0.82 195 5.39 Methane ice 0.53 91 14.9 Nitrogen ice 0.88 63 24.3 ________________________________________________________________ * Assuming the temperatures at Mercury (r = 0.39 AU) and Jupiter (r = 5.2 AU) were 1400 K and 200 K during the condensation phase of the solar system, respectively, other distances were estimated from a simple power law formula. Exercise 3: Atmospheres of Objects in the Solar System The ability of an object to hold on to an atmosphere mostly depends on three items: its mass, its temperature (determined by its distance from the Sun) and the components of the atmosphere. Because liquids require specific ranges of temperatures and pressures to exist, atmospheres are also key to understanding the presence or absence of various liquids on a planet’s surface.
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