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Exam 2 Study Guide

Exam 2 Study Guide - ASTRONOMY 180 INTRODUCTION TO...

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ASTRONOMY 180 INTRODUCTION TO ASTRONOMY STUDY GUIDE--EXAM #2 FALL 2007 1. What are the three types of spectra? Absorption – continuous color with black lines; Continuous – all colors; Emission – dark black continuous with colored lines 2. What are Kirchhoff’s Three Laws of Spectroscopy? Be able to identify the type of spectrum produced with the characteristics of the source. Law 1 – a solid, liquid or dense gas produces a continuous spectra ; a complete rainbow of colors without any spectral lines: a blackbody spectra (light bulb) Law 2 – a rarefied (opposite of dense) gas produces an emission line spectra – a series of bright spectral lines against a dark background (neon light) Law 3 – The light from an object with a continuous spectrum that passes through a cool gas produces an absorption line spectrum – a series of dark spectral lines among the colors of the rainbow (sunlight) 3. How does the movement of electrons among the energy levels of an atom explain the formation of absorption and emission lines? As the photon is absorbed by the electron, the electron moves outward to a higher level causing absorption lines; as a photon is emitted, the electron moves inward to a lower level causing emission lines 4. What type of spectrum do we get from stars? Absorption line spectra 5. What is the Doppler Effect? What causes it? The change in wavelength of radiation due to relative motion between the source and the observer along the line of sight 6. When do you get a blueshift of the spectral lines? When do you get a redshift of the spectral lines? Blueshift - shift toward shorter wavelengths; the Doppler shift of light from an approaching source; redshift – shift toward longer wavelengths; the Doppler shift of light from a receding source 7. What is the radial velocity of a star? How is it measured? The portion of an object’s velocity parallel to the line of sight; measured by taking the speed of the source measured along the line of sight between the source and the observer and dividing it by the speed of light 8. What is proper motion? The change in the location of a star on the celestial sphere 9. Discuss three pieces of information that the spectral lines can provide about a star. The chemical composition of a star by observing the spectra; how fast the star is moving away from or toward the Earth based on Doppler shift; and the temperature of the star based on the continuum 10.What is the order of the planets outward from the Sun? Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, (Pluto) 11.Where are the asteroid belt, Oort Cloud, and Kuiper Belt? Asteroid belt – between Mars & Jupiter; Kuiper Belt – between Uranus & Pluto; Oort Cloud – outside the orbit of Pluto & Eres 12.What are the differences between the terrestrial, Jovian, and dwarf planets?
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