Astro 1 - Daily Outlines ----- Key Concepts - realtime!! on OHP 2 Astro1 - Daily Review I Course Information II. Nature of science and astronomy A. Most things are 1. too tiny or vast too notice... 2. or too fast or slow to notice... 3. or outside the visual range in the electromagnetic spectrum. 4. A lot of things are just plain dark. 5. Cosmic Horizon. B. Scientific Method 1. Intuition is limited! 2. But the universe is logical 3. Notion of "Theory" ----- ----- The SKY - Review: I. Daily Motions of the Sun and Stars 1. Solar and Stellar Motions from Poles, Equator, and in Between 2. Star trails and Circumpolar Stars 3. Northern stars stay up longer. 4. One fist = 10 degrees II. The Celestial Sphere 1. Star patterns nearly fixed 2. Celestial coordinates like Earthly ones ----- The SKY - Review III. The SEASONS: 1. Sun appears to move along the "Ecliptic" great circle on Celestial Sphere 2. Sun is *up longer in summer, and shines *more directly downward 3. TOGETHER these cause the seasons! Both effects are ultimately caused by the tilt of Earth's equator (and the Celestial Equator) relative to the Earth's orbital plane (and the Ecliptic) ----- IV Motions, Faces, and Phases of the Moon Key concepts 1. Moon circles Celestial Sphere in about a month, following a Great Circles close to, but not the same as, the Ecliptic 2. Phases, moon's position in its orbit, and rise and set times are all connected. 3. Just see one side!! Moon must be ROTATING exactly as fast as it's REVOLVING! ----- V ECLIPSES 1. Lunar Eclipses: Moon in Earth's shadow umbra/penumbra 2. Solar Eclipses: Earth in Moon's shadow total/partial/annular need to be in right place at the right time! ----- VII Planetary Motions Key Concepts 1. They all stay NEAR the ecliptic 2. The Inferior ones stay near Sun, are seen in morning or evening twilight; and go through phases 3. The Superior ones circle the Celestial Sphere going West to East, except for Retrograde period. ----- CELESTIAL MECHANICS (Ch 4) I. Kepler's Laws 1. Planets orbit the Sun in ellipses, with the Sun at one focus 2. A given planet moves faster when closer to the Sun; The line joining Sun and planets "sweeps out equal area in equal times" 3. Two different orbiting bodies obey period "P" squared is proportional to the semi-major axis "a" cubed. II. Newton's Laws 1. A body stays at rest or in uniform motion unless acted on by a force 2. When a force acts, the acceleration a = F/m and it's a VECTOR equation 3. For EVERY force exerted by one body on another, the second body exerts an equal and opposite force on the first body. III. Gravity 1. There are two clues to discovering the gravity law F = G m1 m2 / d^2. The block and feather demo shows the force is proportional to the masses involved. The comparison of the apple to the Moon shows the 1/d^2 part. 2. MANY applications such as tidal forces, finding "extrasolar" planets, getting the masses for double stars, space travel, discovery of "Dark Matter," discovery of black holes. LIGHT (Ch 5) I. The Electric Force Field II. A flying force field: an electromagnetic wave. III. Opaque bodies obey the blackbody laws: Stefan-Boltzmann and Wein. IV. To understand more complex spectra we need to know that electrons are constrained to "orbit" in certain energy tracks; a photon can only be emitted or absorbed if it's energy E = hv is equal to the gap between two "orbits." V. Kirchoff's Laws for absorption and emission lines. VI. Doppler Effect ------------------------------------------------------------------------------- The PLANETS! I. Overview of the Solar System 1. Terrestrial planets are small, dense, rocky, close to the sun, warm. Jovian planets have huge amounts of light gases H and He. 2. Interstellar clouds are made of tiny rocks, snowflakes and other icy crystals, and the superabundant light gases H and He. They gravitationally contract and start rotating quickly so they end up in a pancake shape. 3. The sublimation (or "condensation") temperatures are ~2000K for the rocks and metals, and ~300K for the ices. H and He are always gaseous in space. Near the Sun, only the rocky and metallic elements were tough enough to be solid and to form into the terrestrial planets. In the outer solar system however, where the temperature was below ~300K, the "ices" also participated. Thus the outer protoplanets grew fairly massive; that plus thecold temperatures in that region allowed them to capture H and He by gravity - and thus to grow very large. The Terrestrial Planets 1. Earth convection in "mantle" layer causes plate techtonics, which has many effects on Earth's geography and recylcing of carbon dioxide. The terrestrial planet temperatures are set by the solar radiation absorbed, PLUS the extra warming of the ground due to the Greenhouse effect. This is the trapping of the infrared blackbody radiation from Earth's surface by our atmosphere. The NATURAL greenhouse effect on Earth is good and makes it livable but now we're adding substantially to it, and heating up the planet with various dire consequences beginning to occur! 2. Venus's surface is extremely hot because it has a very strong natural greenhouse effect! 3. Earth also has another severe artificial human-induced atmospheric problem, the great weakening of the ozone layer, which allows cancer-causing ultraviolet radiation to reach the surface! 4. Mars has no liquid water today, though it does have ice caps and subsurface ice. Topographic features and physical and chemical evidence from the rovers now on Mars show that it DID have liquid water, and more Earthlike, life- friendly conditions in the past! The Gas Giant Planets 1. The Jovian planets are thought to have rocky cores, extremely deep liquid H and He oceans, and a very thick atmosphere, also mostly made of H and He. Jupiter's blue cloud layer has temp. and pressure like Earth, and clouds of water droplets. 2. The stripes on Jupiter and Saturn are "jet streams," conveying heat from the interior to the cloud tops. 3. Saturn's rings - ice chunks, thinner than paper - snowball size to truck size. 4. Jupiter's 4 Galilean moons: Io covered with erupting volcanoes; Europa also heated tidally - seems to be icebergs on a liquid water ocean - place to look for life! 5. Saturn's moon Titan: big, with thick atmosphere, maybe hydrocarbon "rain" and "oceans." Outer moons mostly ice. ---------------------------------------------------------------------------- Key Concepts for The Sun 1. Hydrostatic equilibrium sets size 2. Huge gravity requires huge pressure. Since density is low, that means extremely high T in center 3. Energy source: Shrinkage (Kelvin-Helmholtz) viable for only 30 million years of contraction; nuclear energy efficiency 0.7% will last many billions of years. 4. Nuclear energy is from fusion of H to He; important details of how it works, 5. We can make accurate inferences (from a "mathematic model") of conditions inside Sun and stars! --------------------------------------------------------------------------- The Stars! I. d, L, R, T II. The HR Diagram III. The Main Sequence IV. Spectral Types V. Red Giants VI. Final Stages of Evolution of Low-Mass Stars: He fusion, planetary nebulae, white dwarfs. VII. Final Stages of Evolution of High-Mass Stars A. Fusion of all heavy elements up to Iron: B. Plot of mass per nuclear particle for each element C. Deaths of massive stars: Supernovae, neutron stars, and black holes VIII. Neutron Stars: A. Neutron stars observed as pulsars B. Testing Einstein's theory of gravity with a binary neutron star IX. Black Holes A. How to find them! B. General Relativity, Einstein's theory of gravity C. Spacetime near Black Holes D. The Supermassive Black Hole in the center of the Milky Way!! ----------------------------------------------------------------- Key Concepts The Stars 1. Solar and stellar models, 7 equations and 7 unknowns, including Equations of State (pressure formula), Equation for Hydrostatic Equilibrium, and Equation for nuclear energy generation 2. Hydrogen fusion into Helium 3. H-R Diagram 4. Spectral types of stars 5. Main sequence Mass/luminosity/lifetime relations 6. HR Diagram and the ages of star clusters 7. Equation of State (pressure formula) for ordinary and for degenerate gases 8. Giant branch, Horizontal branch, and Asymptotic Giant branch. Nuclear binding energy curve: fusion and fission reactions. 9. White Dwarfs and Planetary Nebulae 10. Supernovae, elemental abundances in our Solar System 11. Neutron Stars Radius 10km! Spinning magnet makes flashlight beam! 12. Black Holes Neutron degeneracy pressure failes to hold the star up for greater than 2-3 Mo. No surface! but we see effects of gravity, and infalling matter glowing in X-rays. Effects of Einstein's theory of gravity become crucial so we break for in introduction. BLACK HOLES! I. Special and General Relativity Theories A. Poserful Evidence for G.R. (Einstein's theory of gravity): the Binary Pulsar B. A Spacetime Diagram C. Flatland, key to spatial curvature D. Flatland gravity is a DIMPLE into the 3rd spatial dimension MOVIES II. Black Holes A. How to find them! B. Statement of General Relativity C. Spacetime near a Black Hole D. The supermassive black hole at the exact center of our Milky Way galaxy! Key Concepts Newton's and Einstein's theories agree for weak gravity Binary Pulsar orbit ROTATES and DECAYS as Einstein predicted Statement of GRT: Completely new type of theory for gravity! Matter follows something analogous to a straight line in "curved spacetime." Gravity is (in part) a DIMPLE into a 4th spatial dimension -stretched infinitely by a BH. Time is also stretched infinitely by a BH The Supermassive Black Hole in the Milky Way center! The MILKY WAY AND OTHER GALAXIES I. The Supermassive Black Hole at the Exact Center of the Milky Way. II. Absorption and Reddening of Starlight and Sunlight. III. Galactic Structure. Populations I and II. IV. Dark Matter in the Milky Way and Other Galaxies A. Evidence for Dark Matter B. Machos and Wimps Key Concepts 1. Population 1 and 2 2. We can infer 10^11 Mo inside the solar circle, but 10^12 Mo outside it, where there are few stars!! ----------------------------------------------------------------------- Expansion of the Universe, and the First 3 Minutes! I. Hubble's Law, and FIVE STUNNING CONSEQUENCES II. Evidence for the Big Bang (Universe is expanding and has a finite age) 1. Hubble Law 2. Olbers' Paradox 3. Cosmic Microwave Background 4. Ages of star clusters and white dwarfs 5. Various evidence for evolution with lookback time 6. Light elements III. The First 3 Minutes: Production of the light elements! Key Concepts 1. Hubble's Law, and other evidence such as the Cosmic Microwave Background for a 14 billion year age 2. Conditions in the First 3 Minutes of the Bang are perfect for cooking up the very LIGHT elements not made in stars!!!!