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Electromagnetic Spectrum

Electromagnetic Spectrum. Visible light and color Energy, frequency, wavelength A bit on telescopes Uses. Why do we care about light?. Everything we know in astronomy comes from light We only have physical samples from the Moon, Mars, and a couple comets Even these we study using light.

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Electromagnetic Spectrum

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  1. Electromagnetic Spectrum • Visible light and color • Energy, frequency, wavelength • A bit on telescopes • Uses

  2. Why do we care about light? • Everything we know in astronomy comes from light • We only have physical samples from the Moon, Mars, and a couple comets • Even these we study using light

  3. Electromagnetic Radiation • Radiation: when things are sent out into empty space • EM radiation: light • Nuclear radiation: result of nuclear reactions, includes • Alpha particles (Helium nucleii) • Beta particles (positrons = anti-matter electrons) • Gamma “particles” (gamma EM radiation)

  4. What is Light? • Electric and magnetic fields waving • Packets of energy called photons • Energy and wavelength determine what the light can interact with

  5. http://www.yorku.ca/eye/spectrum.gif

  6. False Color Images • Pictures attempt to “translate” invisible light to what we can see. • Representative color – colors have meaning, such as specific non-visible colors or chemicals • “Touch the Universe” by Noreen Grice

  7. High EnergyHigh FrequencyShort Wavelength

  8. High EnergyHigh FrequencyShort Wavelength • Interacts with small things (cells, molecules, DNA) • Created by high energy / hot processes

  9. http://upload.wikimedia.org/wikipedia/commons/9/99/EM_Spectrum3-new.jpghttp://upload.wikimedia.org/wikipedia/commons/9/99/EM_Spectrum3-new.jpg

  10. ϒ-ray (gamma) and X-ray • High energy, short wavelengths • On Earth: radioactivity, some cancer treatment, broken bones, cavities • Astronomy: high energy processes, hot environments, colliding stars, around black holes, gas around galaxies, the Sun http://today.slac.stanford.edu/images/2007/swift-gamma-ray-lg.jpg http://www.atnf.csiro.au/people/mdahlem/img/xmmtel.gif

  11. Ultraviolet (UV) • Slightly higher frequencies and shorter wavelengths than humans can see • Some birds and insects can see in the UV • On Earth: suntans, sunburn, cancer, can be used to sterilize equipment • Astronomy: Used to study the Sun and other hot objects • Hubble is mostly visible, but does have one UV instrument http://sohowww.nascom.nasa.gov/data/realtime/eit_195/1024/latest.html

  12. Visible light and color • A small part of the total spectrum • Approximately 400-700nm, 4000-7000Å, violet to red • Each color the eye can see has a different wavelength.

  13. http://solarsystem.nasa.gov/deepimpact/images/Spect-Prism-sm.jpghttp://solarsystem.nasa.gov/deepimpact/images/Spect-Prism-sm.jpg

  14. Why do our eyes see with Visible light?

  15. Atmospheric Windows Wavelength, Energy Frequency High flying air planes or satellites Need satellites to observe

  16. Why do our eyes see with Visible light? • Atmospheric windows • Visible and Radio get through an Earth-like atmosphere • Wavelength determines size of things it can interact with • Due to evolution, sizes of our eyes, sizes of molecules in our eyes, we see visible light

  17. Low EnergyLow FrequencyLong Wavelength

  18. Low EnergyLow FrequencyLong Wavelength • Interact with larger things • Lower energy processes

  19. http://upload.wikimedia.org/wikipedia/commons/9/99/EM_Spectrum3-new.jpghttp://upload.wikimedia.org/wikipedia/commons/9/99/EM_Spectrum3-new.jpg

  20. Infrared (IR) • Slightly longer wavelength and lower frequency than the human eye can see. • Some animals including some snakes, some bats, and some insects can see IR. • On Earth: IR goggles help firefighters, soldiers, and home insulation experts; TV remote controls, Kinect • Astronomy: IR travels through dust so is good to look at young forming stars. (e.g., James Webb Space Telescope, HST’s successor) http://upload.wikimedia.org/wikipedia/en/c/cf/Ir_girl.png

  21. Microwave/Sub-mm/Radio • Low energy, long wavelength • On Earth: microwave ovens, cellphone signals, radio for stereos, (formerly) TV broadcasts, GPS, walky-talkies, satellite communications, GPS, weather radar, radar guns • Astronomy: cool objects such as clouds of dust, gas clouds, entire galaxies, SETI, Cosmic Microwave Background (light from the Big Bang) http://apod.nasa.gov/apod/image/0302/sky_wmap_big.jpg http://cache.eb.com/eb/image?id=96170&rendTypeId=4

  22. Bad Science: “Listening” to Radio Like all types of light, radio light is studied using either images or spectra (graphs of the “colors” – brightness at each wavelength)

  23. Nancay Radio Telescope

  24. http://upload.wikimedia.org/wikipedia/commons/9/99/EM_Spectrum3-new.jpghttp://upload.wikimedia.org/wikipedia/commons/9/99/EM_Spectrum3-new.jpg

  25. Each part of the wavelength tells us part of the story.Must put together all wavelengths to get the full story. http://www.thunderbolts.info/tpod/2006/image06/060123nebula.jpg

  26. Example: The Sun • http://sohowww.nascom.nasa.gov/data/realtime/realtime-update.html • Putting these together helps us understand the layers of our dynamic Sun.

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