Astronomy Test 1 Study Guide - ASTR 1345
Astronomy Test 1 Study Guide - ASTR 1345 ASTR 1345-004
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This 6 page Study Guide was uploaded by Sera (Notetaker) on Saturday October 1, 2016. The Study Guide belongs to ASTR 1345-004 at University of Texas at Arlington taught by James J Davis in Fall 2016. Since its upload, it has received 35 views.
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Date Created: 10/01/16
Note taker: Sera ASTR 1345 Astronomy Test 1 Review The Space Race Russia o Wernher von Braun was the head of the Nazi rocket program; his rockets were used for military purposes although he wanted them used for space travel o Von Braun went to work for NASA after the war o Sputnik was the first artificial satellite to orbit the Earth in 1957 o Laika was the first higher form of life in space, launched on Sputnik II in 1957 o Yuri Gagarin was the first person in space in 1961 o The first manned spacecraft to orbit Earth was Vostok 1 o First woman in space was named Valentina Tereshkova US o Robert Goddard developed early rocket models in Roswell, New Mexico o Project Mercury Alan Shepard was the first American in space John Glenn was the first American to orbit Earth Gus Grisom was the second American in space o Project Gemini Included orbital docking a rendezvous with two Mercury space crafts Ed White completed the first American space walk o Project Apollo Largest engineering feat in history Led to the development of the massive Saturn V rocket Apollo 1 was a failed test of the Command Module and a rehearsal of the take-off procedures which led to the death of 3 astronauts Apollo 8 was the first manned lunar orbiter completed on Christ 1968 by Bill Andrews, Frank Borman, and Jim Lovell (these men DID NOT set foot on the moon, merely orbited it) th US was the only country to land people on the moon (July 29 , 1969) consisting of a 3-man team: Neil Armstrong, Edwin “Buzz” Aldrin, and Michael Collins Neil Armstrong spoke the famous “One small step for man, one giant leap for mankind” line as he stepped onto the moon Next generation NASA manned spaceflight vehicles will be named Orion General Space Stuff o Outer space begins where there is too little air to provide lift to conventional aircrafts ~120km above Earth o Cassini probe currently orbits Saturn o The Curiosity rover studies Mars o New Horizons recently flew past Pluto in 2015 o Juno currently orbits Jupiter o NASA’s future missions include: Asteroid capture & Mars sample return Note taker: Sera ASTR 1345 The Night Sky Ancient Astronomy o Ach mammoth tusk carving - ~38,000 years old (Germany) Man on front (possibly Orion) Birth calendar on back o Lascaux cave paintings - ~20,000 years old (Lascaux, France) May show familiar constellations and sky features The Pleiades – a bright, tight cluster of young stars “Man, Bird, & Bull” might have been attempts to draw the constellations of the Summer Triangle o Nebra Disk - ~1600 BC (Germany) Ornamental disk Oldest unequivocal representation of the cosmos Shows the sun and moon, as well as locations of the sunsets/sunrises, and the Pleiades Astrology o Interpreting astronomical influence on human affairs and events Constellations o A group of stars visibly related to one another in the sky o Constellations were tributes to gods and heroes o They were used to track seasons and to identify regions of the night sky Aristotle (384-322BC) o Greek philosopher o Created a theory about the mechanics of the world that was mostly wrong Geocentric (Earth-centered) Planets were spheres (instead of flat) with perfect circular orbits It was known that the planet was not flat due to that fact that shadows were different lengths in different places at the same time; as well because the North Star changed positions in the sky depending on the observer’s location Could not predict the position of the planets The celestial sphere was an outer spherical shell of stars that surrounded the Earth Planets (Greek for “wanderer”) were contained in physical spheres that one could not go past North Celestial Pole o A straight line running through the North Pole of the Earth which connects to the Celestial sphere o Points almost directly at Polaris, the “North star” Celestial Equator o The equator of the Earth projected out into space o Divides the sky into northern and southern hemispheres o Measured in declination (analogous to lines of latitude on Earth) Note taker: Sera ASTR 1345 o North Pole - +90 degrees declination o Equator – 0 degrees declination o South Pole - -90 degrees declination o If you are in Arlington at 32.7 degrees north latitude on Earth, the line of declination 32.7 degrees passes over your head on the celestial sphere The Ecliptic o The imaginary path that the Sun takes across the sky over the course of the year o Sometimes referred to as “the Zodiac” it contains the 12 zodiac constellations (technically 13 constellations) o The high and low points on the ecliptic refer to the summer and winter solstice, and the two middle points refer to the spring and vernal equinox o Right ascension on the celestial sphere is analogous to longitude and is measured in hours, minutes, and seconds Precession o The gradual wobble of the Earth which causes the direction of the axis to shirt over 26,000 years o Today: axis points at Polaris o 2700 BC: axis pointed at Thuban in Draco o 12000 AD: axis will point at Vega in Lyra o Precession causes the zodiac signs to shift over time, meaning the zodiac signs of back then are not the zodiac signs of today o The moon keeps Earth relatively stable, keeps us from wobbling around too much The Moon Earth’s closest celestial neighbor Various phases of the moon are caused by different regions of the moon receiving sunlight during the lunar month Waxing is when the light side of the moon is growing (light side is on the right) o A waxing crescent moon forms the curve for a “b” for light bigger igger Waning is when the light side of the moon is shrinking growing (light side is on the left) o A waning crescent moon forms the curve for a “d” for light decreasing ecreasing Sidereal period o The time it takes the moon to complete one orbit in relation to the back ground stars (27.3 days) Synodic period o The time it takes the moon to return to the same angle in relation to the Sun & Earth (29.5) o This period takes longer because the Earth is in motion around the sun while the moon is trying to realign with the Sun and Earth once again Note taker: Sera ASTR 1345 Solar Eclipse o Occurs when the Earth falls into the shadow of the Moon o Only occurs when there is a new moon o Moon blocks out the sun (sometimes completely, sometimes only partially) Lunar eclipse o Occurs when the moon falls into the shadow of the Earth o Only occurs during a full moon o Turns the moon blood red It turns red because Earth’s atmosphere scatters blue light more than red light (the reason why the sky is blue), so more red light passes through the atmosphere, allowing it to hit the moon during a lunar eclipse and turn it red Great Minds in Astronomy Major features of Aristotle’s Universe o Unchanging universe o Earth-centered o Perfect circular orbits of unchanging speed with perfect spherical bodies Ptolemy (90-168 AD) o Greek astronomer & geographer o Wanted to make Aristotle’s model fit reality o Wrote “The Almagest,” or “Mathematical Syntaxis” o Supported and strengthened the geocentric model TheEquant–thenotionthattheEarthwasslightlyoffcenterfromthecenter of the universe, but everything still orbited Earth Epicycles – used to explain retrograde motion of planets, an orbit on top of an orbit Ptolemy added however many epicycles he needed to to planets, such as Mars, in order to explain their orbits (Mars ended up having 37 epicycles) Retrograde motion o The apparent motion of planet to reverse direction and travel backwards for a time before reversing again and travelling in its original direction once again o All planets appear to do this from Earth at different rates o This occurs because the Earth is orbiting the Sun while the other planets orbit sun as well, causing us to catch up to slower planets in their orbit, creating the appearance that they are traveling backwards Science o Science must have falsifiability, in other words, one must be able to prove a theory wrong for it to be considered science Nicolaus Copernicus (1473-1543 AD) o The “first Astronomer,” Polish mathematician o Wrote De Revolutionibus Orbium Coelestium o Supported a heliocentric model of the universe Note taker: Sera ASTR 1345 His model eliminated epicycles and accurately explained retrograde motion Tycho Brahe (1546-1601) o Dutch astronomer; greatest naked eye astronomer o Measured star and planet positions with great precision using parallax (the apparent motion of distant objects due to an observer’s movement) Johannes Kepler (1571 – 1630) o Worked under Tycho Brahe o Argued for the Copernican model of the universe o Figured out that orbits were elliptical An ellipse is a flattened center with two centers (foci) With an ellipse a planet as a point when it is closest to the sun- perihelion- and a point when it is furthest from the sun- aphelion o Kepler’s 3 Laws of orbital motion st 1 law: the orbit of a body about the Sun (or any star) is an ellipse with the sun’s center of mass at one focus (circular orbits are super rare, but large planets have orbits close to perfect circles) 2 law: A line joining a planet and the sun sweeps out equal areas in equal tird intervals 3 law: The square of a planet’s period is proportional to the cube of its orbital radius (the time it takes to revolve around the sun depends on how close a body is to the sun) Galileo Galilei (1564-1642) o One of the first creators of the telescope, pioneer in the field of observational astronomy o Fourtelescopicobservations which disprovedAristotle’s theoryoftheuniverseand proved the heliocentric model Galilean moons (which he called the DeMedician stars) of Jupiter Phases of Venus Sunspots Mountains on the moon Isaac Newton (1643-1727) o Creator of Calculus and Physics o Interested in motion, gravity, and optics o Laws of Motion; first coherent, scientific description of motion; universal and deterministic 1 law: An object in motion stays in motion and an object at rest stays at rest unless acted upon by an outside force (law of inertia) 2 law: The acceleration of an object is proportional to the force acting on it (F=ma) 3 law: For every action there is an equal and opposite reaction from the object being acted on o Mass & Weight Mass – number of particles contained in an object Note taker: Sera ASTR 1345 Weight – force of gravity felt by an object o Gravity Gravity is universal, it exists within everything in the universe Gravityis mutual, gravitational force is “shared” by a pair of objects, which are bound to each other, exerting the same force on one another Objects orbit around a common barycenter which is the center of mass of the system
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