Spectroscopy Astronomers can learn an immense amount from the details of lines in the spectrum of light coming from planets and stars. This tool is used by chemists, biologists, physicists and all of the other natural sciences. It is based on the quantum or particle (photon) nature of light.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Astronomers can learn an immense amount from the details of lines in the spectrum of light coming from planets and stars.
This tool is used by chemists, biologists, physicists and all of the other natural sciences.
It is based on the quantum or particle (photon) nature of light.
Introductory Spectroscopy Applet
Emission Line Spectrum
Absorption Line Spectrum
Spectra of astrophysical objects are usually combinations of these three basic types: how they arise is described by Gustav Kirchhof’s Laws.
Helium: 2 p + 2 n
Nuclei -- protons and neutrons with essentially all the mass of the atom.
Electrons are in orbitals which define atomic energy levels-- essentially fill the volume.
Carbon: 6 p + 6 n
“Classical” model -- not a very good approximation
Probabalistic electron cloud-- wave function
Emission and absorption lines from Na gas;
Yellow Doublet (two nearby wavelengths)
Hydrogen spectra: on top, molecular: H2
On bottom: simpler atomic: H
Cause of Doppler Effect
Star Motion Doppler Applet
Reflected Sunlight: Continuous spectrum of visible light is like the Sun’s except that some of the blue light has been absorbed - object must look red
Thermal Radiation: Infrared spectrum peaks at a wavelength corresponding to a temperature of 225 K
Carbon Dioxide: Absorption lines are the fingerprint of CO2 in the atmosphere
Ultraviolet Emission Lines: Indicate a hot upper atmosphere
Peer Instruction Question: from our galaxy), then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milky Way Galaxy.Suppose you observed the spectrum of sunlight reflected from Mars. Compared to the spectrum of the sun observed directly, it would