Infrared Astronomy and Activities
Dan Burns
Los Gatos High School
Lawrence Livermore National Lab
http://education.llnl.gov/academies/?page=home
Overview
• What is Infrared Radiation (IR)?
• Discovery of IR
• IR Astronomy
• IR Observatories
• Classroom Activities
NASA/JPL-Caltech
• IR is bounded by Visible Light and Microwave Radiation
• Wavelengths from about 0.7 to 350 microns
• Primary Source is Thermal Radiation
• Humans can sense it with nerves in skin
• Snakes can “see” IR with Pits (Pit Vipers)
IR Characteristics
NASA/JPL-Caltech
Thermal Radiation• Emitted by materials with relatively strong molecular
or atomic bonds (ie solids and liquids)
• Every object with a T > 0 K emits thermal radiation
• Produced by random motions of charged particles
• Radiation peak, usually in IR, can be used to determine temperature
NASA/JPL-Caltech NASA/JPL-CaltechNASA/JPL-Caltech
William Herschel
• German Immigrant to England
• Discovered Uranus in 1781
• Catalogued Night Sky with Sister Caroline
• Discovered IR in 1800
NASA/JPL-Caltech
Herschel’s IR Experiment
• Investigated heat of colors in spectrum
• Temperature increased from violet to red
• Placed a thermometer beyond red, this measured greatest temperature increase
http://www.sciencemuseum.org.uk/on-line/treasure/objects/1876-565.asp
Student Herschel Experiment
• Materials: Copy Paper Box, Smaller Box, White Paper, Tape, Equilateral Glass Prism, Black Paint, Timer, 3 Thermometers, Sunlight!
• Time Required: ~ 30 minutes
NASA/JPL-Caltech
Equipment Setup
• Paint Thermometer Bulbs Black
• Trim and Tape Thermometers Close Together
• Cut Opening for Prism and Mount it
• Tape White Sheet of Paper to Bottom of box
NASA/JPL-CaltechNASA/JPL-Caltech
Procedure Outline
• Position Box and Prism so Spectrum Shows
• Record Shade Temperature
• Place Thermometers, 1 each in Blue, Yellow, and IR
• Record Temperatures at 1 minute intervals for 5 minutes
NASA/JPL-Caltech NASA/JPL-Caltech
NASA/JPL-Caltech
Typical Results
NASA/JPL-Caltech
Why Infrared Astronomy?• Almost Everything Emits IR
• IR Passes Through Dust
• Exoplanets Easier to Detect in IR
• Distant Object’s Visible Light Redshifted
• Important Molecular Spectra in IR
Credit: ESA/ISO, SWS, A.F.M. Moorwood
IR Reveals the Invisible
Interstellar Dust Emits IRNASA/JPL-Caltech
Spitzer Shows a Warped Sombrero Galaxy
http://www.spitzer.caltech.edu/Media/mediaimages/index.shtml
Spitzer Reveals Stars and the Galloping Ghoul
http://www.spitzer.caltech.edu/Media/mediaimages/index.shtml
IR Uncovers What is Hidden
Spitzer Space Telescope Reveals Star Formation in DR21
Visible
IR
NASA/JPL-Caltech
Spitzer Zooms into the Triffid Nebula
http://www.spitzer.caltech.edu/Media/mediaimages/index.shtml
IR Discovers Dim Objects
UK IR Telescope Discovers Brown Dwarfs and Potential Free-Floating Planets in Orion
Image courtesy of the U.K. Infrared Telescope, Mauna Kea Observatory, Hawaii
IR Detects Distant Objects
Visible Light from Very Distant Galaxies is Redshifted to IR
Important Molecular Spectral Lines are in IR
IR Space Observatory Reveals Water Molecules being Produced in Orion Nebula
Spitzer Detects Structures in Polycyclic Aromatic Hydrocarbon Dust
http://www.spitzer.caltech.edu/Media/mediaimages/index.shtml
Detecting IR
• Near, Mid, and Far IR
• Atmospheric Absorption
• IR Observatories
NASA/JPL-Caltech
Image courtesy of the U.K. Infrared Telescope, Mauna Kea Observatory, Hawaii
Near, Mid, and Far IR Bands
Visible Near Mid
NASA/JPL-Caltech
NASA/JPL-Caltech
Atmosphere Impedes IR Observation• Water Vapor Absorbs Some IR Wavelengths
• Atmosphere Emits its own IR Radiation
NASA/JPL-Caltech
Past, Present, and Future IR Observatories
IRAS
HSTESA Herschel
UKIRT
SST
NASA/JWST
SOFIA
NASA/JPL-Caltech
Image courtesy of the U.K. Infrared Telescope, Mauna Kea Observatory, Hawaii
NASA/STScI
Infrared Processing and Analysis Center, Caltech/JPL. IPAC is NASA's Infrared Astrophysics Data Center
NASA/USRA
Student Activities
• Herschel Experiment
• IR Photo Album
• Solar Cell IR Detector
• Near IR Digital Camera
• IR Detection Cards
• Red Tide Spectrometer with LabQuest
http://spaceplace.jpl.nasa.gov/en/kids/sirtf1/sirtf_action.shtml
for activity
IR Photo Album Resources
http://coolcosmos.ipac.caltech.edu/videos/more_than_your/index.html
Cool Cosmos Website
Herschel Experiment Resources
• http://coolcosmos.ipac.caltech.edu/cosmic_classroom/classroom_activities/herschel_experiment.html for detailed activity
• www.sciencekit.com for prism (catalog # WW65664M00 $8.95) and thermometers (catalog # 6638910 $13.25 for 10-Pack)
Solar Cell IR Detector Resources
• www.radioshack.com for Mini Audio Amplifier (Catalog # 2771008 $14.99), Solar Cell (Catalog # 277-1201 $13.99),
• 6’ Cable (Catalog # 42-2420 $3.29)
• http://www.sofia.usra.edu/Edu/materials/activeAstronomy/activeAstronomy.html for detailed activity information
Near IR Digital Camera• Webcams, Digital Cameras, or Camcorders
• Remove IR Blocking Filter from CCD
• Install IR only pass filter (Wratten 87c, exposed color negative, or floppy disk)
• Reassemble and view the world in Near IR
• Sony Nightshot Camcorder has switch to remove IR blocking filter
IR Filter Spectral Characteristics
IR Detection Cards
• 2 Types of Materials can Produce Visible Light When Exposed to IR from a Remote Control
• Anti-Stokes Material Absorbs 2 or More Photons for Every Visible Photon Emitted
• Phosphorescent Material Must be Exposed to Visible Light First
• See Activity from KSU Physics Education Group
Anti-Stokes Model
Phosphorescent Model
Red Tide and SpectroVis Spectrometers
•Red Tide and SpectroVis Spectrometers by Vernier•Automatically reads the wavelength calibration coefficients of the spectrometer and configures operating software•USB to PC or Mac interface; no external power requirements•The Red Tide starts at $1732, SpectroVis at $449•Optical Fibers are extra
IR Emission from a Green Laser
• Some Green Lasers allow IR at 802 nm and 1064 nm to leak out
• If IR reflects off surfaces that pass green it can be dangerous
• This IR can be measured with a simple experiment, see below for more info:
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=906138
California Science Standards• Earth Science 2d: Students know that stars differ in their
life cycles and that visual, radio, and X-ray telescopes may be used to collect data that reveal those differences.
• Physics 4e: Students know radio waves, light, and X-rays are different wavelength bands in the spectrum of electromagnetic waves.
• Chemistry 1i, 1j Students know the experimental basis for the development of the quantum theory of atomic structure and the historical importance of the Bohr model of the atom. Students know that spectral lines are the result of transitions of electrons between energy levels and that these lines correspond to photons with a frequency related hv). to the energy spacing between levels by using Planck’s relationship
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