1. Newton’s Experiments with Light

2. Electomagnetic Waves

3. Properties of Waves: Frequency and Wavelength

5. Telescopes Yerkes Refractor Arecibo Radio Disk Mauna Kea Hubble Space Telescope

6. Resolution of Telescopes

7. Sensitivity of Telescopes

8. The Earth’s Shroud The Earth’s atmosphere acts to “screen” out certain kinds, or bands, of light. Visible light and radio waves penetrate the atmosphere easiest; the IR somewhat. Most other bands are effectively blocked out. Consequently, telescopes are built at high altitude or placed in space to access these otherwise inaccessible bands.

9. Transparency of the Atmosphere

10. Transmission with Altitude

12. Flux of Light Light carries energy (e.g., perceived warmth from sunlight) How does this energy propagate through space? And how does that relate to the apparent brightness of a source? “Flux” describes how light spreads out in space: with L=luminosity (or power), and d = distance, flux is Watts/square meter = J/s/m 2

13. The Inverse Square Law

14. Kirchoff’s Laws I.A hot solid, liquid, or dense gas produces a continuous spectrum of emission. II.A thin gas seen against a cooler background produces a bright line or emission line spectrum. III.A thin gas seen against a hotter source of continuous radiation produces a dark line or absorption line spectrum.

15. Kirchoff’s Laws: Illustrations

16. Blackbodies 1. A common approximation for the continuous spectrum produced by many astrophysical objects is that a blackbody (or Planckian). 2. A blackbody (BB) is a perfect absorber of all incident light. 3. BBs also emit light!

17. Temperature Scales

18. Temperatures of Note

19. Sample Blackbody Spectra

20. Atomic Physics Atoms composed of protons, neutrons, and electrons p and n in the nucleus e resides in a “cloud” around the nucleus m p /m n ~1 m p /m e ~2000 Protonsp+1mpmp Neutronsn0mnmn Electronsememe

21. The Bohr Atom

22. Atomic Energy Level Diagram

23. Interaction of Matter and Light Absorption: Occurs when a photon of the correct energy moves an electron from a lower orbit to an upper orbit. Emission: Occurs when an electron drops from an upper orbit to a lower one, thereby ejecting a photon of corresponding energy Ionization: Occurs when a photon knocks an electron free from the atom Recombination: Capture of a free electron

24. Absorption and Emission

25. The Gross Solar Spectrum Blackbody-likeBlackbody deviations

26. Thermal Motions of Particles in Gases

27. Doppler Shift The Doppler effect is a change in,, E of light when either or both the source and detector are moving toward or away from one another. So, this is a relative effect.

28. Illustration of the Doppler Effect

29. Composition of the Universe

30. Brief Overview of Stellar Evolution Pre-Main Sequence (really short time): The phase in which a protostar forms out of a cloud of gas that is slowly contracting under gravity Main Sequence (long time): The phase in which a star-wannabe becomes hot enough to initiate and maintain nuclear fusion of hydrogen in its core to become a true star. Post-Main Sequence (sorta short time): H-burning ceases, and other kinds of burning may occur, but the star is destined to become a White Dwarf, Neutron Star, or Black Hole

31. Formation of Stars and Planets Observational Clues from the Solar System: 1.Orbits of planets lie nearly in ecliptic plane 2.The Sun’s equator lies nearly in the ecliptic 3.Inner planets are rocky and outer ones gaseous 4.All planets orbit prograde 5.Sun rotates prograde 6.Planet orbits are nearly circular 7.Big moons orbit planets in a prograde sense, with orbits in equatorial plane of the planet 8.Rings of Jovians in equatorial planes 9.S.S. mass in Sun, but angular momentum in planet orbits

36. Accretion and Sub-Accretion

38. Collection of Planetesimals into Planets

39. Solar Nebula Theory Immanuel Kant (German): 1775, suggested that a rotating cloud that contracts under gravity could explain planetary orbit characteristics Basic Modern View – 1.Oldest lunar rocks ~4.6 Gyr 2.Planets formed over brief period of 10-100 Myr 3.Gas collects into “disk”, and cools leading to formation of condensates 4.Growth of planetesimals by collisions a)Build up minor bodies and small rocky worlds b)Build up Jovian cores that sweep up outer gases

40. The Chaotic Early Solar System Recent computer models are challenging earlier views that planets formed in an orderly way at their current locations These models suggest that the jovian planets changed their orbits substantially, and that Uranus and Neptune could have changed places These chaotic motions could also explain a ‘spike’ in the number of impacts in the inner solar system ~3.8 billion years ago The Moon and terrestrial planets were bombarded by planetesimals early in solar system history.

41. The model predicts: 1.After formation, giant planet orbits were affected by gravitational ‘nudges’ from surrounding planetesimals 2. Jupiter and Saturn crossed a 1:2 orbital resonance (the ratio of orbital periods), which made their orbits more elliptical. This suddenly enlarged and tilted the orbits of Uranus and Neptune 3.Uranus / Neptune cleared away the planetesimals, sending some to the inner solar system causing a spike in impact rates Cosmic Billiards The early layout of the solar system may have changed dramatically due to gravitational interactions between the giant planets. Note how the orbits of Uranus and Neptune moved outwards, switched places, and scattered the planetesimal population. 20 AU planetesimals 100 Myr 880 Myr 883 Myr~1200 Myr J S U N

42. The Big Picture The current layout of our solar system may bear little resemblance to its original form This view is more in line with the “planetary migration” thought to occur even more dramatically in many extrasolar planet systems It may be difficult to prove or disprove these models of our early solar system. The many unexplained properties of the nature and orbits of planets, comets and asteroids may provide clues. Artist’s depiction of Neptune orbiting close to Jupiter (courtesy Michael Carroll)

43. Bode’s Law PlanetBode’sActualError Mercury0.4 <1% Venus0.7 <1% Earth1.0 Perfect Mars1.61.57% Asteroids2.8 <1% Jupiter5.2 <1% Saturn10.09.55% Uranus19.619.22% Neptune---30.0Miserable Pluto38.839.42% ??77.2---

44. Radiative Equilibrium

45. Global Temperatures of Planets PlanetPredictedActualError (K) (%) Mercury44040010 Venus23073068 Earth25028011 Mars2202105 Jupiter10512516 Saturn809516 Uranus60 <1 Neptune456025 Pluto40 <1

46. Density and Composition (kg/m 3 ) Water1000 Rock3000 Air1.3 Brass8600 Steel7830 Gold19300 (kg/m 3 ) Ices1000 Volcanic rock and stony meteorites 2800 - 3900 Iron rich minerals 5000 - 6000 iron~7900 Ex: Moon –  (surf) ~ 2800 and ~ 3300 Earth –  (surf) ~ 2800 but ~ 5500