ESO s Paranal Observatory VLT Telescopes Credit ESO B Tafreshi Course Announcements Welcome to the 2nd day of Fall Autumnal Equinox was yesterday Exam 1 will take place Wednesday 28 Sept Will cover Chapters 1 4 Study Materials Now Available Must Knows Chapter Slides and MA Study Guide Study sessions next Monday and Tuesday evenings combined with A151 A151 Primary Monday Night at 5 30 6 30 PM A152 Primary Tuesday Night at 5 30 6 30 PM Both in Room 304 Assignments Reading Assignments No new reading Parallel Lectures No new parallel lectures Mastering Astronomy Chapter 4 Homework Due Monday 26 Sept at 11 59 PM EDT Wavelengths in ngstroms Spec tral Hydr Seri ogenes n 2 Balmer Series Visible Light Photons Transitions starting or ending at the 1st Excited State n 2 Ener gy Diagr am Lyman Series UV Photons Transitions starting or ending at the Ground State n 1 n 1 Spectrum of Hydrogen A spectrum of an element gives us a view of the energy structure of that element s electron energy levels H H Hydrogen Beta H Hydrogen Alpha H The Balmer Series Visible Light Emission Absorption Atoms heavier than Hydrogen More protons more electrons more complicated energy structure more complicated spectral lines New Energy Structure More protons and electrons means different electrical structure of atom Helium Carbon Different electron orbital energy levels More electrons means more transitions means more spectral lines 2 Protons 2 Electrons 6 Protons 6 Electrons Atoms heavier than Hydrogen More protons more electrons more complicated energy structure more complicated spectral lines Hence each ion has it s own set of spectral lines Ionized spectral lines e g doubly ionized Oxygen lines or ionized He lines andNeutral spectral lines the ones we have already discussed Carbon 2 Protons 1 2 Electrons 6 Protons 5 6 Electrons 4 3 Ionization Comlications Multiple stages of ionization loss of electrons Each ionization changes the energy structure Helium Spectrum of an Emission Nebula Omega Nebula M17 nebula means gas cloud The Emission Spectrum tells us about the composition of the nebula Think of the white squiggly line as the number of photons measured of each wavelength of light More intensity means more photons of that color Hence the red glow Molecular Lines A more complex scenario A molecule is tightly bound group of atoms held together by interactions between their orbiting electrons chemical bonds More ways to absorb or release energy Still quantized Molecular Lines Spectral Line Formation Still have electronic transitions UV Visible and Near Infrared lines Molecular Vibrations bending and stretching of the chemical bonds Infrared Lines Molecular Rotations Microwave and Radio Lines Molecular Lines Atomic Hydrogen versus Molecular Hydrogen H2 Molecular Hydrogen or Diatomic Hydogen H2 Atomic Hydrogen H Spectral Line Analysis What information is contained in spectral lines Chemical Composition Temperature Rotation State Radial Velocity Density and Pressure Magnetic Field Strength Spectral Thermometer Where are the electrons How excited or ionized The presence absence and strength how bright of a spectral lines are all indicative of temperature Radial Velocity Applying the Doppler Effect Part I Motion toward or away from the observer Run Away Run Away redshifted blueshifted Blueshift Case with H change in wavelength recession velocity true wavelength wave speed It s coming right for us Line Broadening Spectral lines are not infinitesimally thin they are spread out over a small range of wavelengths Spectral lines are broadened due to 1 2 3 4 Thermal motions of particles Rotation of a macroscopic object Collisions between atoms Magnetic Fields Zeeman Effect Thermal Broadening Temperature Applying the Doppler Effect Part II Random motions of particles also affect by Doppler Effect Random motion speed and direction means atoms have some component moving toward or away an incoming photon or vice versa The Doppler Shift applied to that photon or atom spreads out the precise energy required for absorption or emission This broadens the the spectral line Most of the atoms statistically have small thermal velocities so Doppler shifted only small amount Gives shape of line Collisional Pressure Broadening Particles bump into each other with some energy which will slightly offset the specific acceptable photon energy The energy associated with the collision between two particles needs to be accounted for Number of collisions depends on the density and of the gas Hence widths of spectral lines can give us density of the gas Rotational Broadening Applying the Doppler Effect Part III A rotating body has components moving toward us or away from us Magnetic Field Broadening The Zeeman Effect A fundamental property of electron orbitals is a magnetic component the details see Quantum Mechanics The end result is when exposed to a magnetic field the electron orbital energies split due to the intrinsic magnetic moment and hence the transition energies wavelengths of photons absorbed or emitted changes How far the energy levels split depends on the strength of the magnetic field This will broaden the How split spectral lines tl dr Magnetic fields split spectral lines Why Quantum Mechanics is weird gives mag field Telescopes CHAPTER 5 Class Question What is the primary purpose of telescopes with respect to viewing astronomical objects What do we want to do to the objects we observe Top Sloan Telescope Middle 1 m robotic telescope Bottom 3 5 m Apache Point telescope Apache Point Observatory Sunspot New Mexico Class Question Answer It s not magnification making things bigger we are after but rather it s making faint things brighter We want to be able to see as much of the universe as possible and most of it is very very dim Top Sloan Telescope Middle 1 m robotic telescope Bottom 3 5 m Apache Point telescope Apache Point Observatory Sunspot New Mexico What is a telescope Basic important facts A telescope is a tool whose primary function is to capture as much light as possible from a region of the sky or object and concentrate the light focus into a narrow beam for analysis A light bucket Big thing to capture as many photons as possible Focuses light with lenses or mirrors A detector of some kind is required to analyze or capture that light Your eye photographic plates film CCDs etc Taken together a telescope is a series of lenses and or mirrors that focuses concentrates light and puts that concentrated light on a detector Refracting
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