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CORNELL ASTRO 1102 - Exam 1 Study Guide

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ASTRO 1102 1st Edition Exam # 1 Study Guide Lectures: 1 - 8Lecture 1 (January 21)Our Solar System: Course Introduction- Inner planets differ from outer planets. The former are mostly made of rock and metal, and the latter are exponentially larger and composed of various gases.- Solar System: Consists of the sun, the planets and their moons, and countless smaller objects that include asteroids and icy comets.- Milky Way Galaxy: The disk-shaped collection of stars our solar system belongs to; contains over 100 billion stars.- Galaxy: A great island of stars is space, containing between a few hundred millionto a trillion or more stars.- Local Group: The ~40 galaxies group near us, including the Milky Way.- Galaxy Clusters: Groups of galaxies with more than a few dozen members.- Superclusters: Essentially, clusters of galaxy clusters, where galaxies are most tightly packed. Our Local Group is located on the outskirts of our Local Supercluster.- Universe: The sum total of all matter and energy.- Observable Universe: The portion of the entire universe that can be seen fromEarth; it is probably only a tiny portion of the entire universe.- Rotation: The spinning of an object around its axis.- Orbit (revolution): The orbital motion of one object around another due to gravity.- Expansion (of the universe): The increase in the average distance between galaxies as time progresses.- Nuclear fusion: How a star generates energy; the process in which light-weight atomic nuclei smash together and stick/fuse to make heavier nuclei.- Astronomical Unit (AU): Earth’s average distance from the sun; 150 million km/93million miles = 1 AU.- Light-Year (ly): The distance that light can travel in one year; 10 trillion km/6 trillion miles = 1 ly.- Because light takes time to travel through space, the farther we look into the distance, the further back we look in time.Lecture 2 (January 23) The Sky and Historical Astronomy- The Main Point: The movements of the Sun, Moon, planets, and stars that we observe every day and night are apparent, not actual motions, because we are moving as well!- Horizon: 360 degrees around,where the Earth’s surfaceintersects with the apparentposition of the sky.- Zenith: The point directlyoverhead, which has analtitude of 90° (straight up).- Celestial Sphere: The imaginarysphere on which objects in thesky appear to reside whenobserved from Earth; it is auseful construct forunderstanding the geometry ofEarth’s horizon, zenith, rotationaxis, etc.- Celestial Pole: A projection of Earth’s equator into space; makes a complete circlearound the celestial sphere. North Celestial Pole: The point directly over Earth’s North Pole. South Celestial Pole: The point directly over Earth’s South Pole.- Celestial Equator: The extension of Earth’s equator onto the celestial sphere.- Rotation Axis: The axis upon which the Earth spins.- Latitude: The angular north-southdistance between Earth’s equator anda location on Earth’s surface.- Longitude: Measures east-westposition; defined to be 0° at the primemeridian.- Ecliptic: Earth’s orbital plane/path;also the apparent path of the sun inthe sky.- Obliquity: The tilt angle of the Earth(about 23.5°).- The Zodiac: A group of constellationsalong the ecliptic that the Sun appearsto travel through.- Astrology: An ancient system of beliefsthat claimed that the positions of theSun, Moon, and planets governed theactions and events in our lives; hasbeen proved wrong.- Constellation: A region of the sky with well-defined borders; the familiar patternsof the stars merely help us locate the constellations.- Nicholas Copernicus: Proposed the heliocentric model.- Ptolemy: Proposed the geocentric model.- Aristotle: Concluded that the earth is round.- Eratosthenes: Derived diameter (and thus the size) of the Earth.- Aristarchus: Discovered the relative size of the Earth, Sun and Moon.- Galileo Galilei: Provided observations that validated the heliocentric model; first to create a true astronomical telescope and use it; discovered sunspots, the moons of Jupiter (1609), explored the features of the Moon, and discovered the phases of Venus; used math to describe acceleration.- Geocentric model: Proposed that Earth is a sphere that stayed motionless at thecenter of the universe; the moon sun and other known planets would orbit around Earth.- Heliocentric model: Earth and other planets orbit around the Sun; only the Moonorbits Earth.Lecture 3 (January 26) Orbits and Gravity- The Main Point: Motions of planets moons, asteroids, and comets can be very accurately predicted because of the underlying laws of planetary motion and gravity discovered by Kepler and Newton.- Tycho Brahe: Provided high-quality data to test the competing geocentric and heliocentric models.- Johannes Kepler: Took Tycho Brahe’s data and with them proposed The Laws of Planetary Motion, which explain how the planets move.- Kepler’s First Law: The orbit of each planet around the Sun is an ellipse, with the Sun at one focus. - Kepler’s Second Law: As a planet moves around its orbit, it sweeps out equal areas in equal times.- Kepler’s Third Law: More distant planets orbit the sun at slower average speeds, obeying a precise mathematical relationship: p2 = a3 p = the planet’s orbital period in years a = the planet’s average distance from the Sun in astronomical units (AU) - Ellipse: A special type of oval; it is the shape of the orbits in which the planets travel.- Foci (sing. focus): The two ends of an elliptical orbit.- Major Axis: The long axis, or diameter, of the ellipse.- Semi-Major Axis: Half the length of the major axis; measured from the center of the ellipse. - Eccentricity: A quantity that describes how much an ellipse is stretched out compared to a perfect circle.- Perihelion: Point of approach closest to the Sun in orbit- Aphelion: Point of approach farthest away from the Sun in orbit- Speed: The rate at which an object moves. Its units are distance divided by time, such as m/s or km/hr.- Velocity: The combination of speed and direction of motion; it can be stated as a speed in a particular direction, such as 100 km/hr due north.- Acceleration: The rate at which an object’s velocity changes. Its standard units are m/s2.- Acceleration of Gravity: The acceleration of a falling object.- Momentum: The product of an object’s mass and velocity (m x v).- Force: Anything that can cause a change in momentum.- Angular Momentum: Momentum attributable to


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