Frontiers of Astronomy Community Event " Clearing Our View of the Universe with Robo -AO,"

1. 1st Extra credit event Frontiers of Astronomy Community Event "Clearing Our View of the Universe with Robo-AO," ChristophBaranec(UHIfA) Wednesday, October 8, 2014, 7:30 p.m., UH Mānoa Art Building Auditorium (room 132). Free Admission When we peer out into the Universe with ground-based optical and infrared telescopes, Earth's atmosphere limits the clarity of our vision. Adaptive optics (AO) systems counteract the blurring effects of the atmosphere and greatly increase the acuity of our observations. In this talk, Dr. Baranec will review the technology behind adaptive optics and talk about the world's first fully automated laser adaptive optics instrument, Robo-AO. Dr. Baranec joined the faculty at the University of Hawai‘i's Institute for Astronomy in 2013. He is interested in pushing the limits of adaptive optics technology to shorter wavelengths, wider fields, and greater sky coverage, with the ultimate goal of broadening our understanding of the Universe through high-resolution imaging. His awards include a research fellowship from the Alfred P. Sloan Foundation (2014).

2. Homework #4 • A set of keys is dropped from the top of the Empire State building in New York. How fast will they be going when they hit a poor tourist on the ground 9 seconds later? • How tall is the Empire State Building? • An astronaut drops his set of keys from the same height as the Empire State Building on the Moon (1/6th the gravity of Earth), how fast is it going when it hits the Lunar surface?

3. Gravitational Potential Energy for the surface of the Earth is: (where r is the radius of the Earth) and: So, Gravitational Potential Energy

4. Escape Velocity set: ½ m v2 = GmME/r for a mass m to escape from the Earth (of mass ME) ½ v2 = GME /r vesc= 2GME /r

5. What is light?

6. Four Ways in Which Light can Interact with Matter emission – matter releases energy as light absorption – matter takes energy from light transmission – matter allows light to pass through it reflection – matter repels light in another direction

8. But, what is light? • In the 17th Century, Isaac Newton argued that light was composed of little particles while Christian Huygens suggested that light travels in the form of waves. • In the 19th Century, Thomas Young demonstrated that light bends slightly around corners and acts like interfering waves.

9. Light A vibration in an electromagnetic field through which energy is transported. Dual Nature f  = c Light as a wave Light as a particle E = hf photon E af Planck’s constant h = 6.6 x 10-34 J s

10. Scottish physicist James Clerk Maxwell showed mathematically in the 1860s that light must be a combination of electric and magnetic fields.

12. Anatomy of a Wave

13. Light as a Wave • For a wave, its speed: s = [distance/time] =  f But the speed of light is a constant c = 3 x 108 m/s • For light:  f = c and f= c /  • The higher f is, the smaller  is, and vice versa. • Our eyes recognize f (or ) as color!

14. Light as a Particle • Light can also be treated as photons – packets of energy. • The energy carried by each photon depends on its frequency (color) • E = hf = hc /  (h = 6.6 x 10-34 J s) • Bluer light carries more energy per photon.

15. Interaction ofLight with Matter Hydrogen • Remember that each electron is only allowed to have certain energies in an atom. • Electrons can absorb light and gain energy or emit light when they lose energy. • It is easiest to think of light as a photon when discussing its interaction with matter. • Only photons whose energies (colors) match the “jump” in electron energy levels can be emitted or absorbed.

16. Light as Information Bearer We can separate light into its different wavelengths (spectrum). • By studying the spectrum of an object, we can learn its: • Composition • Temperature • Velocity

18. Dividing Light Into a Spectrum Astronomers separate out light into its individual components using a diffraction grating or using a prism - then they analyze each part independently!

19. blue 460 nm 81 Filter Detector 81

20. blue 460 nm 81 Filter Detector 85 green 530 nm 85

21. blue 460 nm 81 Filter Detector 83 green 530 nm 85 yellow 580 nm 83

22. blue 460 nm 81 Filter Detector 78 green 530 nm 85 yellow 580 nm 83 orange 610 nm 78

23. blue 460 nm 81 Filter Detector 70 UV IR green 530 nm 85 yellow 580 nm 83 orange 610 nm 78 red 660 nm 70 The spectrum is continuous.

24. Natural Spectra ????

25. Änuenue (rainbow) Light from the Sun Water droplet

30. Shine Light through Hydrogen…

31. Shine Light through Hydrogen…

32. Shine Light through Hydrogen… 397 434 486 656 410

33. l (mm) = (mm=10-6m) 1.24 [mm eV] E [eV] E = hn = hc/l g l = hc/E E = hn = hc/l E = hn h=Planck’s constant;n=frequency [Hz=1/s]; l=wavelength [m]

34. 397 434 486 656 410 E(3 g 2)= 12.07-10.19 = 1.89 eV

35. l (mm) = (mm=10-6m) 1.24 [mm eV] 1.24 1.89 E [eV] l(3 g 2) = ~ 0.656 mm

36. Shine Light through Hydrogen… 397 434 486 656 410

37. Thermal Radiation

38. Rules for Emission by Opaque Objects • Hotter objects emit more total radiation per unit surface area. • Stephan-Boltzmann Law: • P/A= T4(s =5.7x10-8[Watt/m2Kelvin4]) • Hotter objects emit bluer photons (with a higher average energy.) • Wien Law: • max = 2.9 x 106 / T (K) [nm]

39. What have we learned? • What is the escape velocity of the Earth? • If an object travels fast enough, it will escape the gravitational pull of the Earth. The speed needed can be calculated by setting the gravitational potential energy at the surface of the Earth to the expression for kinetic energy and solving for the speed necessary to overcome the pull of the Earth. ½ mv2 = mgh remember 7/11 (7 mi / s or 11 km/s)

40. What have we learned? • What is universal law of gravity? F = G m1m2 r2 What does this formula mean? If you double a mass what happens to the force? If you half the distance, how does the force change?

41. What have we learned? • How are speed, wavelength, and frequency related for a wave? • The wavelength is equal to the speed divided by the frequency • What is meant by the dual nature of light? • Light sometimes behaves like a particle (photon) and at other times like a wave. This is a first hint that all things have a dual nature – behaving both as particles and waves. • What is the relationship between the energy for light and its amplitude, frequency, or speed? • The energy associated with light is independent of its amplitude. Also, since all light travels at the speed of light, Energy is also independent of speed. The energy is however directly proportional to the frequency (color) of the light.

42. What have learned? • What is light? • Light is an electromagnetic wave that also comes in individual “pieces” called photons. Each photon has a precise wavelength, frequency and energy. Forms of light listed in increasing energy are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays

43. What have we learned? • What are wavelengthand frequency for light? Wavelength is the distance between two parts of a wave that are the same and frequency is the number of waves that pass a point per second. Hertz (1/sec) is the unit of frequency. • How do light and matter interact? Matter can emit, absorb, transmit, or reflect light. You can only see your neighbor because light is reflected off of them! ln = c E = hn = hc/l

44. How does light tell us what things are made of? Every kind of atom, ion, and molecule produces a unique set of spectral lines. How does light tell use the temperatures of planets and stars? We can determine temperature from the spectrum of thermal radiation What have we learned?

45. What are the possible orbits allowed by gravity? elliptical, hyperbolic, parabolic What have we learned?