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PH1600: Introductory Astronomy Lecture 3 What is this? PH1600: Introductory Astronomy Lecture 3: Universe Scale, and Light School: Michigan Technological University Professor: Robert Nemiroff Online Course pages: http://courses.mtu.edu/ This class can be taken online ONLY, class attendance is not required! You are responsible for… Lecture material Listed wikipedia entries But not higher math APODs posted during the semester In class, iTunes, learnoutloud.com APOD review every week during lecture Completing the Quizzes Chapter 1 quiz is now due Chapter 2 quiz is due soon See WebCT at http://courses.mtu.edu/ Wikipedia entries (Lecture 3) Black body Spectrum Spectral line Bohr model Doppler Effect 4 Black Body Spectrum A plot of intensity versus energy emitted by an object The highest intensity will usually determine the object’s color Stars of different temperatures will have different spectra The spectrum can be uncovered Pass light through a prism http://commons.wikimedia.org/wiki/Image:Blackbody-lg.png Black Body Spectra Prism (optics) From Wikipedia, the free encyclopedia An Iridescent Cloud Over Colorado Credit & Copyright: August Allen APOD: 2007 November 25 8 Stellar Spectral Types: OBAFGKM Credit & Copyright: KPNO 0.9-m Telescope, AURA, NOAO, NSF APOD: 2001 May 30 Absorption Lines Gasses absorb very specific colors of light Different gasses absorb different colors Hydrogen atoms absorb very specific colors that can be identified Helium first discovered on the Sun through its absorption lines All the Colors of the Sun Credit & Copyright: Nigel Sharp (NSF), FTS, NSO, KPNO, AURA, NSF APOD: 2007 June 24 The Bohr Atom Outdated but useful atomic model Electrons orbit a central proton Created by Neils Bohr in 1913 Much like planets orbit the Sun Only certain orbits allowed, called energy levels Electrons falling down emit a photon Electrons absorbing a photon get bumped up Bohr model From Wikipedia: http://commons.wikimedia.org/wiki/Image:Bohr-atom-PAR.svg Atomic Absorption and Emission Spectra From: http://csep10.phys.utk.edu/astr162/lect/light/absorption.html Emission Lines Same colors as absorption lines except they are bright instead of dark Emission nebulas typically appear red because They are primarily hydrogen Bright H-alpha emission line emitted in the visible range (red) when an electron falls from the n=3 energy level to the n=2 level The Rosette Nebula Credit & Copyright: Robert Gendler 2007 February 14 The N44 Emission Nebula Credit & Copyright: WFI, MPG/ESO 2.2-m Telescope, La Silla, ESO APOD: 2006 February 13 Emission and Reflection in NGC 6559 Credit: Robert Gendler APOD: 2001 October 23 Wisps Surrounding the Horsehead Nebula Credit & Copyright: Star Shadows Remote Observatory APOD: 2006 February 21 The Doppler Shift Heard with sound every day Occurs with light, too! Light is blueshifted – all photons are more energetic Source moving away from you Allows you to go bowling with a flashlight Source moving toward you Train whistles, cars whizzing past, etc. Light is redshifted – all photons are less energetic All photons always move at speed c Signed, "A Black Hole" Credit: B. Woodgate (GSFC), G. Bower(NOAO), STIS Instrument Definition Team, NASA APOD: 1997 May 16 21 This Week in APOD Next week: Observing Stars and Planets