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. http://www.lcse.umn.edu/specs/labs/images/spectrum.gif

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

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

7. 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

8. High Energy High Frequency Short Wavelength

9. Interacts with small things (cells, molecules, DNA) Created by high energy / hot processes

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

11. ϒ -ray (gamma) and X-ray http://today.slac.stanford.edu/images/2007/swift- gamma-ray-lg.jpg http://www.atnf.csiro.au/people/mdahlem/img/xmm tel.gif 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

12. 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

13. 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.

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

15. http://wfc3.gsfc.nasa.gov/MARCONI/images-basic/spectrum.jpg

16. Why do our eyes see with Visible light?

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

18. 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

19. Low Energy Low Frequency Long Wavelength

20. Interact with larger things Lower energy processes

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

22. Infrared (IR) http://upload.wikimedia.org/wikipedia/en/c/cf/Ir_gir l.png 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)

23. Microwave/Sub-mm/Radio http://apod.nasa.gov/apod/image/0302/sky_wmap_big.j pg 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://cache.eb.com/eb/image?id=96170&rendTypeId=4

24. 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)

25. Nancay Radio Telescope

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

27. 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/image06/060123 nebula.jpg

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