ASTR 151 1nd Edition Exam 1 Study Guide Lectures 1 2 5 and 6 1 Lecture 1 Chapter 1 a Scientific Theory must have beauty simplicity and comprehensiveness i Scientific Theories can be proven wrong but can t be proven right with 100 certainly b Scientifics Law does not explain why something works it merely states that something works with no evidence to back up the claim c Scientific Method is a constant cycle d The universe is a totality of all space time and matter measured in light years e Observation leads to theory theory is best proven by observation The Science Circle of Life f Ancient Romans grouped the stars together to form Constellations groupings that have meaning and purpose g Astronomers use the celestial sphere to gain two dimensional coordinates based on latitude and longitudinal lines of the earth h Angular Measure is used with a base of 10 It depends on the size of the star itself 2 Lecture 2 Chapter 1 a Solar day is a daily cycle in diurnal motion b Sidereal Day is stars that aren t always in the same place after one earth rotation c Earth s orbit is ecliptic where the path is tilted 23 5 degrees to celestial equator d Summer solstice northern point of the path closest to the sun Winter Solstice Southern point of path closest to the sun e Day length and sunlight makes the seasons f Precession a complete 26 000years rotation of earth s axis g Synodic Month is a complete 29 5days rotation for the moon s cycle h Moon s phases are made by different amounts of sunlit portions that are visible from Earth i Sidereal Month is two days shorter than synodic month the moons rotation around the earth j Moon s phases Waxing crescent 3rd quarter Waning Gibbons Full Moon Waxing Gibbons 1st quarter Waxing Crescent and New Moon k Lunar eclipses occurs when the earth is between the Moon and Sun light from the earth is reflected from the earth l Solar eclipses occur when the moon is between the sun and the earth m Solar eclipses partial occurs when part of the sun is blocked n Solar eclipses annular occurs when the moon is too far from earth o To measure earth s radius use measuring angle and distance between two cities 3 Lecture 3 Chapter 2 a Astronomers observe the Sun Moon Stars and five planets Mercury Venus Mars Jupiter and Saturn b Planets seemed to Undergo retrograde motion orbits in a circular motion and then randomly orbits backwards c Inferior planets are never too far from the Sun Superior planets are unattached to the sun s gravity d Geometric Model made by Claudius Ptolemy put earth in the center and needed 80 circles as orbit models e Copernicus retained perfect circles as orbit models in his model All planets revolved around the sun f Aristarchus of Samos believed the sun was the center of our universe g Heliocentric Model sun at the center with only the moon orbiting earth h Telescopes were built around 1600s i Galileo built his own telescope which later blinded him published Sidereus Nuncius and deemed a heretic 4 Lecture 4 Chapter 2 a Tycho Brahe last of the naked eye astronomer observed comets and new stars i Made the Tychonic system merge between Ptolemic and Copernican models Earth doesn t move but planets orbit the sun b Johannes Kepler created the laws of motion Kepler s Laws c Planetary Motion Laws i Planetary orbits are ellipses with the Sun in the Center ii Imaginary line connecting Sun and planet sweeps out equal areas in equal times iii Square of period of Planet s orbital motion is proportional to cube of semi major axis d Solar System Dimensions i Astronomical units measure the distance between the earth and sun AU 5 Lecture 5 Chapter 2 a Newton s 3 Law i Explains how objects interact with world and with each other Vector Direction and Magnitude ii Newton s Laws 1 An object at rest tends to stay at rest 2 F m a 3 For every action there is a reaction b Newton s Mechanics i G Gravitational force is weight aimed towards the center of the mass ii Kepler s laws are consequence of newton s laws first law should be modified iii The force keeping the planets in orbit around the Sun is the gravitational force due to the masses of the planet and sun 6 Lecture 6 Chapter 5 a Optical Telescopes collects visible light and focuses it at one point i Visible light small part of the electromagnetic spectrum energy ii Reflective 1 Reflecting mirror depends on the size of the lens 2 Large lens work best but they are very heavy a Types four i Prime ii Neurtonian iii Cassegrain iv Nasmyth coud e focus iii Refractive 1 Change in direction with a transmission medium 2 Lenses depend on energy frequency and wavelengths of light 3 Chromatic aberration iv Sizes 1 Larger mirrors can gather more information 2 Angular Resolution is the smallest distance between two resolvable objects and measured in arc seconds v Images detectors 1 Image acquisition is subdivided be 2demisional array of pixels 2 Computers analyze and process and analyze images vi Atmospheric blurring called seeing point sources out as speckle platters 1 Long exposure images 7 Lecture 7 Chapter 5 a Radio Astronomy i Adaptive Optics real time changes in atmosphere ii Telescopes Prime focus type resolution still depends on wavelength iii Advantages Less sensitive to imperfections due to longer wavelength and observes for a full 24 hours b Interferometry amount of interference depends on the direction of signal i Can be done in the light but difficult to absorb ii Electro magnetic signals combines information from widely spread plates are super imposed to get information about the waves 1 Construct in phase sound waves move in unison 2 Destruct out phase sound waves move out of unison c Space Base Astronomy 1 Infrared Telescope Produces images where visible radiation is blocked ii Gamma Rays 1 Can t be focused at all so images are blurry 2 X rays will reflect if it happens to come in fairly shallow d Full Spectrum Coverage i James Webb his telescope looks for light dating to the Big Bang of the universe also can see infrared ii Redshift wavelength changes based on motion away and toward observer as well as speed iii Cosmo Redeshift shows the universe still expanding 1 Depends on how quickly and object moves 8 Lecture 8 Chapter 6 a Eight planets were added to the official records b More than 800 extra solar planets have been found c Density m v Radius is found through observation d Radius is found from angular size e All orbits are on the same plane roughly except for Mercury f Terrestrial i Small rocky close to the Sun
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