Reading Notes 7.1-7.3.docx

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Astronomy & Astrophysics
Michael Reid

Reading Notes 7.1-7.3 Section 7.1 Major Motions in the Solar System: -Large bodies in the solar system have orderly motions -All planets have nearly circular orbits going in the same direction in nearly the same plane -Most large moons orbit their planets in the same direction -Which is also the direction of the sun’s rotation Sun: -composition is 98% hydrogen and helium, 2% other elements -Largest and brightest object in the solar system -Contains more than 99.8% of solar system’s total mass -Actually a roiling sea of hot hydrogen and helium gas -Gaseous throughout, and the temperature and pressure both increase with depth -Its gravity governs the orbits of the planets -Its heat is the primary influence on temperatures of all surfaces -Its source of virtually all the light in solar system Mercury: -Composition of rocks and metals -Zero moons -Innermost planet of our solar system -Smallest of eight official planets -No active volcanoes, no wind, no rain, no life -World of both hot and cold extremes -Surface is heavily catered -High density indicates it has a very large iron core Venus: -Composition of rocks and metals -Zero moons -Second planet from the Sun -Rotates on an axis very slowly & opposite direction of Earth -Surface is completely hidden from view by dense clouds -Mountains, valleys, craters, & extensive evidence of past volcanic activity -Venus resembles a traditional view of hell Earth: -Composition of rocks and metals -One moon -Only known oases of life in our solar system -Oxygen to breathe -Ozone to shield the surface from deadly solar radiation -Abundant surface water to nurture life -Contains just enough carbon dioxide & water vapour to maintain moderate greenhouse effect -Blue oceans cover ¾ of the surface; rest is continental landmasses and scattered islands Mars: -Composition of rocks and metals -Two very small moons (Phobos and Deimos) -Last of the four inner planets -Mass is 10% of Earth’s -Ancient volcanoes & massive great canyon -Polar caps made of frozen carbon dioxide and water -Evidence of some warm and wet periods in past -Air pressure & temperature are both extremely low -Close to no trace amounts of oxygen -Exposure to deadly ultraviolet radiation from the Sun Jupiter: -Composition of mostly hydrogen and helium -At least 67 moons -Four main moons: Io- most volcanically active Europa- icy crust that hides subsurface ocean Ganymede and Callisto may have subsurface ocean -Mass is more than 300 times Earth’s -No solid surface -Reign over dozens of moons and a thin set of rings Saturn: -Composition of mostly hydrogen and helium -At least 62 moons -Second largest planet in our solar system -No solid surface -Saturn’s rings can be seen easily & made of countless small particles -Particles of rock and ice range in size from dust grains to city blocks -Too cold for liquid water to exist Uranus: -Composition of hydrogen, helium, hydrogen compounds (water, ammonia, methane) -At least 27 moons -Pale blue green colour -Lacks a solid surface -Set of rings are much darker and harder to see -Tipped on its side compared to the rest of the planets -Extreme seasonal variations of any planet in our solar system Neptune:- Composition of hydrogen, helium, hydrogen compounds -At least 13 moons (most fascinating Triton) -Strikingly blue -Triton’s icy surface has features of geysers that spew nitrogen gas rather than water in the sky Dwarf P
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