Radiation and Matter - The Planets - Assignment 6 | ASTR 105G, Assignments of Astronomy

Download Radiation and Matter - The Planets - Assignment 6 | ASTR 105G and more Assignments Astronomy in PDF only on Docsity! Lecture 13 Telescopes ASTR 105G: The Planets March 5, 2009 Announcements 1. HOMEWORK 6: DUE TODAY 2. Tonight is your last chance to see this first set of objects as part of your homework assignment! Turn it in to Cat. 3. Lab this week - Kepler’s Laws Read it - Lab will be held in Jacobs Hall 129 4. Comments on webpage1 Last time ... • We talked about the three main types of astronomical spectra - names?? • Stefan-Boltzmann Law and Wien’s Law • What spectra can tell us about planets and stars • Doppler shifts 1 Radiation and Matter 1.1 Doppler Shift (continued) Doppler Effect • We have all experienced the changing sound of an ambulance or train as it passes by2 • Sound waves are shifted to higher frequencies (shorter wavelengths) as the train is coming towards you and shifted to lower frequencies (longer wavelengths) as it moves away • Moving source animation of Doppler effect3 • The same thing happens for waves of light and radiation - objects moving towards an observer are blue-shifted, objects moving away are red-shifted 1http://astronomy.nmsu.edu/jasonj/AST105/ 2http://www.fourmilab.ch/cship/sounds/doppler.au 3http://www.falstad.com/ripple/ex-doppler.html Lecture 13 March 5, 2009 2 / 5 Figure 1: How our eye works. Why are Doppler Shifts Important for Astronomy • From what we have already said, we know the spectra of atoms. These lines get red- or blue-shifted if the object is moving at some velocity v: v c = λshift − λrest λrest • See animation 5.22 • So we not only know the composition, we know its speed to or away from us • Rotation of an object also shifts an object’s spectrum – Doppler broadening - see drawing • So “reading” light tells us so much information about an object 2 Astronomy with Telescopes 2.1 Principles of Telescopes How Images are Formed Source of Figure 1: http://www.siepser.com/anatomy.htm