ASTR 151 1nd Edition Lecture 4 Outline of Last Lecture II. Summary of Chapter 1III. Chapter 2, The Copernican Revolution 2.1 to 2.4Outline of Current Lecture IV. Review on concepts in Chapter 1V. Tycho BraheVI. Johannes KeplerVII. 2.5 The Laws of Planetary MotionVIII.2.6 Intro to the Dimensions of the Solar SystemCurrent LectureII. Concepts in Chapter 1a. When a parallax angle of a star is measured to be 0.002, the distance to the star is what?i. Distance=1/parallaxii. Parallax is measured in arc secondsiii. Distance is measured in parsecsiv. Parallax=57.3 degrees * Baseline / Distancev. 0.002=5.56e-7 degreesvi. Distance=1.34e12 km=0.14 light yearsb. Mars, Jupiter, and Saturn show retrograde motion because the earth moves faster in it`s orbitc. Copernicus` important contribution to astronomy was the heliocentric modelIII. Tycho Brahea. Last great “naked eye” astronomerb. Made great number of precise measurementsi. “Stellar novae” or new stars didn`t exhibit parallax lacked the parallax expected in sub-lunar phenomenaii. Comets aren`t atmospheric phenomenaiii. Atmospheric tailless comets aren`t as previously believedc. Came up with Tychonic system – a merge between Ptolemic and Copernican modelsi. He made a model where the Earth did not move however all the other planets revolved around the Sun. ii. His model widely failed to the publicThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.IV. Johannes Keplera. As a kid, he saw a comet and a lunar eclipseb. Was a vital proponent to the heliocentric modelc. Originally wanted to become a minister but chose to be a math and astronomy teacher in Graz once the job was offeredd. Assisted Tycho Brahe in Prague in various projectsV. 2.5 The Laws of Planetary Motiona. Purpose; to describe planetary motioni. Planetary orbits are ellipses with the Sun in the center1. Circle = 1 foci coincide2. Semi-major axis = aii. Imaginary line connecting Sun and planet sweeps out equal areas in equaltimes1. When closer to the Sun, you go faster in rotationiii. Square of period of planet`s orbital motion is proportional to cube of semi major axis1. In other words; p^2/a^3 = constantVI. 2.6 Dimensions of the Solar Systema. AU = Astronomical Unit – distance from Earth to the Sunb. Ration of mean radius of Venus`s orbit to that of Earth is very well knownc. Kepler`s laws were derived empirically (which means by
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