Week 3 The Sun and Stars

1. Week 3The Sun and Stars Part I Light, Telescopes, Atoms and Stars

2. The Light of Astronomy • Electromagnetic Radiation • For the most part - all astronomical observations are at distance • E-M radiation is our link

3. Let there be light • Electrical wave perpendicular to Magnetic Wave • Travels 300,000 km/sec (186,000 miles/sec) always (in a vacuum) • The velocity of light is usually called ‘c’ • Wavelength – longer = ‘redder’ shorter = ‘bluer’ • The spectrum

5. Light in Astronomy • Wave Particle Duality • Depending on how you measure/observe light – it seems to act like a wave sometimes and a particle (photon) sometimes • Our intuition says this can’t happen! • Everything in the subatomic world acts like this. • Another way E=mc2 works! • Particles vs. Waves????

6. Quantum Leap

7. Quantum Tunneling

8. Picture a wall with a slit… • Put a light bulb on one side and look at the image made on the wall on the other side of the wall. • What do you expect to see?

9. One Simple Slit

10. One Slit version 2 One bright spot.

11. But Light acts as a wave too…

12. Now what about two slits in the wall?

13. The diffraction Pattern for 2 slits in the wall…

14. What is happening…

15. The truth behind 1 slit: http://www.phys.hawaii.edu/~teb/optics/java/slitdiffr/

16. What if you allow one electron a week to hit the ‘wall’ between two slits?

17. Week 1 Electrons over time Week 2 Week 3 Week 4 Week 5

18. How Light Works:

19. Light • E=hc/lamda --- Energy in Light • h=Plank’s Constant 6.6262X10-34 joule sec • lambda = wavelength, c = speed of light • Frequency (Hz) = c/lamda (m) • e.g. 89.5 MHz (FM) = 335 cm • Short wave Radio 41m = 7.1 Mhz

20. Shedding More Light on It • See figure on next frame • To the right = longer wavelengths • Below AM = Power Cycles (wall current frequency 60Hz Hz = cycles or waves per sec.) • AM-FM, VHF, UHF • Microwave • Infrared • Visible • Ultra-Violet • X- Rays • Gamma Rays • Cosmic Rays (particles)

21. Low Energy HIGH ENERGY

22. Light and Us • The Human Eye

23. Light and Astronomy Optical Telescopes optics Made to operate in 400-700nm range only • Elements of a telescope • Focal Length • Primary / objective • Eyepiece (camera/CCD/human eye)

24. The Eye and the Telescope

25. The Upside(down) of it • This needs to be corrected in binoculars or terrestrial binoculars or telescopes. • Is NOT worried about in telescopes.

26. A camera • Like the eye

27. Upside down!

28. Digital Images • This is how amost ALL astronomy is done today. • Computers can help!

29. Telescopes • Two kinds of telescopes • All based on the glass or mirror that FIRST gathers the light • Called the objective • Lens - refractors • Mirror - reflectors

30. Telescopes • Refractors • First design of telescope • Glass in end catches the light • Focuses it down to eyepiece (lenses) at the back of the tube. • One piece and sealed

31. Telescopes • Expensive and heavy • Hard to keep aligned • Chromatic Aberration

32. Telescopes • The “Power” of a telescope • NOT the most important feature of the telescope • Most important = Light Gathering Area = size of the objective (mirror or lens that first gets a hold of the light) • Larger objective = more rain by r2 relation (area of a circle) • A=pi*r2 • Comparison of light gathering power = ratio of areas • 8” vs. 4” = 82/42 = 64/16 = 4X more light gathering power • Objective size also yields resolving power • Magnification comes from • Focal length telescope/ focal length of the eyepiece (printed on the side of eyepiece) • Smaller chip of glass in eyepiece = more magnification

33. Telescopes • Reflectors see next frame • Newtonian,Prime Focus, Cassegrain, Schmidt-Cassegrain • Newtonian = light out of side near front by diagonal mirror • Prime Focus = Big telescopes or cameras only, observer INSIDE light path • Cassegrain = light out back with parabolic mirror • Schmidt-Cassegrain = light out back with spherical mirror and corrector plate that starts the light focusing (sealed)

35. + a minor variation, Coude’

36. Telescopes • Getting through the atmosphere • Resolving power messed up by atmospheric turbulence • = Atmospheric Seeing = twinkling of stars • alpha = 11.6/D (D = mirror diameter in cm’s). • Transparency (haze and clouds and sky glow) • Light Pollution (from cities/outdoor lighting) • Wind • Local Temperature Effects • Expansion/Contraction • Dew

37. How they are used • Visual Observations (not scientifically often) • Imaging – pictures for study and beauty • Spectroscopy – looking at the makeup of the spectrum • Timing – occultations, variable stars • Visible and non-visible frequencies

38. Telescope Mounts • Alt-Az Mounts • = Altitude and Azimuth motions only • Altitude = straight up and down • Azimuth = back and forth horizontally • Lighter and cheaper • Easier to set up in the field • Easier to maintain • Harder to track the motion of the sky • Computers help with this now

39. Telescope Mounts • Equatorial Mount (German Equatorial Mounts) • One axis points to the north celestial pole = • Mount is tilted equal to your latitude • You have to adjust it when you move more than 50 miles north or south of your favorite spot • Sometime more wobbly than alt-az • Tracks the sky simply around one axis • A sidereal clock can drive the gear (no computer necessary) • Coordinates on mount can be set to match coordinates on start maps and charts • Alignment is necessary for it to work (North Pole axis right on). • Good for photography and star parties

40. Getting a better Look • Mountain Top Locations are best (less seeing and better transparency year round) • Adaptive Optics (New-Generation Telescopes) • Old telescopes = large thick blanks of glass = tons! (200 inch Hale Telescope on Mount Palomar = 14.5tons) • Temperature problems – uneven expansion • Sagging at low altitude tilt • New telescopes have a computer and laser sensor system that constantly checks the shape of the mirror and adjusts it • Segmented Mirror is one type

41. Looking good • Another type is a thin deformable mirror • Mirror shape can also be rapidly updated to reduce the effect of seeing (unblurring the star images).

42. Telescope Improvements • Photographic Plates were the standard… but now; • CCD cameras • =Charge-Coupled Device (where we get modern video cameras from) • Digitizes data which is stored rapidly on computers. The images can be manipulated later • Spectrographs are also in common use • Break the star or nebula light up into a spectrum- element lines become visible (more on this later) • Stored on film or CCD

43. The Biggest Telescopes

44. Top Scopes • The Hubble Space Telescope (and why) • 96 inch mirror • Largest orbiting telescope ever built • Not a very large telescope but it has NO seeing or transparency problems induced by the atmosphere. Also no day (except part of every ~ 90 minute orbit) or weather problems! • Places: • Mountain Tops • Airplanes

45. Other types of Telescopes • Other (research) telescopes • Radio • A big dish (larger than light due to larger wavelength) • Pointing picks up a point value of radio energy • A computer puts it together into a picture later below • Can operate in the day and under clouds • Can pick up clouds of hydrogen gas and other non-stellar emissions • Radio interferometry

46. Radio Telescopes

47. Additional Telescopes – near visible light • UV and IR • The atmosphere absorbs UV (ozone) and IR radiation (water vapor) • Space based telescopes and high mountain (Maouna Kea and Chile and airplane and balloon borne telescopes are the only useful tools • IR = IRAS (Infrared Astronomy Satellite – early 1980’s) • UV = International Ultraviolet Explorer (IUE) 1978

48. High Energy Telescopes • X-Ray & Gamma Ray Telescopes • Also space, balloon and aircraft based • X-Ray = Einstein Observatory • Metal Lenses • More details later

49. The Chandra X-Ray observatory (satellite)

50. TELESCOPES OF THE FUTURE!