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William Herschel

William Herschel

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William Herschel

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  1. William Herschel Discovery of Infrared Radiation - 1800

  2. Build your own Herschel demo

  3. The full electromagnetic spectrum … Making Light of it All!

  4. The Electromagnetic Spectrum Our eyes see only part of the electromagnetic spectrum…

  5. Light is a transverse wave of electromagnetic energy The wavelength (and, reciprocally, the frequency) of light defines its radiation band (X-ray, or Visible, or Infrared, or …) Riding the Wave

  6. Light has a dual nature: It exhibits both wave-like and particle-like properties

  7. FORMULA CONNECTING WAVE & PARTICLE PROPERTIES OF EM RADIATION: E = h c / l E = energy per photon (joules, J) h = Planck’s constant c = speed of light (m s-1) l = wavelength (m)

  8. Infrared Thought of as “heat,” common in daily lives Microwaves Used for communication, cooking Radio Wavelengths of centimeters to kilometers Great for transmissions that need to go far and penetrate buildings Low-energy Light

  9. Gamma Rays Radioactive atoms, nuclear power plants X-Rays Penetrate soft tissue Ultraviolet Tans and sunburns, mostly stopped by atmosphere High-energy Light

  10. Temperature determines themain type of radiation emitted … (left to right: Compton, Chandra, Hubble, and Spitzer space observatories)

  11. “Invisible” Light in Astronomy Each part of the spectrum provides a piece of the puzzle in understanding our universe.

  12. The Pinwheel Galaxy – M101

  13. Multi-wavelength astronomy An object can appear radically different depending on the type of light collected from it: Constellation Orionleft: visual-wavelength viewright: far-infrared view

  14. Visible: dark nebula, heavily obscured by interstellar dust • Near-IR: dust is nearly transparent, embedded proto-stars can be observed • Mid- and far-IR: glow from cold dust is directly observable Visible Near Infrared Mid-Infrared


  16. There’s a problem for IR astronomy... • Earth’s atmospheric water vapor absorbs almost all incoming infrared radiation • Even mountain-top observatories get a limited view of the infrared universe

  17. thermal-IR image of Earth from a weather satellite

  18. View of troposphere / stratosphere boundary from above

  19. And a Solution... • High-flying aircraft --above 40,000 ft -- can observe most of the infrared universe • Airborne infrared telescopes can be more versatile -- and much less expensive -- than space infrared telescopes NASA’s Kuiper Airborne Observatory (KAO) C-141 with a 36-inch telescope onboard, based at NASA-Ames near San Francisco, flew from 1975 - 1995 ,

  20. SOFIA Science Center home page Spitzer Space Telescope’s award-winning infrared tutorial (includes instructions for home-made Herschel demo) Further information:

  21. “Invisible” Light in Society Each part of the spectrum impacts our daily lives… Sunscreen Communications Microwave ovens Remote controls X-rays

  22. The Tools of Our Search We collect light from distant objects, and bring together researchers from many disciplines.

  23. Where did we come from? What is our destiny? Are we alone?

  24. Our Place in the Universe

  25. Searching for Life Are we alone?

  26. JUPITER – heat from formation still escaping

  27. The Orion M42 star-forming region (left to right: visible-l, near-IR, mid-IR)

  28. Looking Back in Time To find the earliest galaxies, we will need to explore the universe in the infrared.

  29. Middle School physical science, High School physics 4 activities comparing and contrasting visual & infrared light Teachers’ guide including curricular material, pre-/post-tests, parts list available at: Active Astronomy (“AA”) classroom kit

  30. Resources • SOFIA Active Astronomy • Stanford Solar Center Spectrascopes and Colors of the Sun video • The Dynamic Sun • Project Spectra • Project Spectra

  31. SOFIA Science Center home page Spitzer Space Telescope’s award-winning infrared tutorial: (includes instructions for home-made Herschel demo) Further information: