Astronomy 1140 -- Autumn 2018 (Prof. Stanek) Final Exam Study Guide (Wednesday, Dec 12th, 2:00-3:45 p.m.) ----------------------------------------------------------- Please bring an OSU ID to the final exam (required). There will be 100 questions on the Final Exam, which will count for 38% of the final grade. As an option, we allow two 8.5x11 "help sheets" (two pieces of paper, both sides of each sheet can be used) of self-prepared (you can use a computer) notes. Classes to review (almost all of them): Units and Scales Mapping the Earth Sky and the Motions of the Sky The Motion of the Sun Telling Time The Motion of the Moon The Calendar The Four Seasons Eclipses The Wandering Planets Greek Astronomy Copernicus Tycho & Kepler Galileo Newton's Laws Newtonian Gravity Applying Newton's Laws; Tides Energy Light Temperature Matter Light and Matter Telescopes Solar System: Overview Age of the Earth The Earth Earth's Atmosphere Impacts The Moon Mercury Venus Mars Jupiter & Saturn Moons of Jupiter and Saturn Uranus & Neptune Kuiper Belt Comets Asteroids Formation of the Solar System Extrasolar Planets I No need to review Fate of the Solar System Extrasolar Planets II Key Concepts: The Celestial Sphere -------------------- (1) The sky as seen from Earth is divided into 88 constellations. (2) It is convenient to pretend the stars are attached to a celestial sphere. (3) The celestial sphere appears to rotate about the celestial poles (1 sidereal day). (4) The Sun appears to move west to east relative to stars (1 year), its path on the sky is called ecliptic. (5) The Moon appears to move west to east relative to stars (1 month). Season & Calendars ------------------- (1) The cause of the seasons is the tilt of the Earth's rotation axis relative to its orbit around the Sun. (2) The solar day is based on the time between one noon and the next. (3) The (tropical) year is based on the time between one vernal equinox and the next. (4) The moon (month) is based on the time between one new moon and the next. Moon Phases & Eclipses ----------------------- (1) Lunar phases change as we see more or less of the Moon's sunlit half. (2) The Moon rotates about its axis as it revolves around the Earth. (3) The sidereal month=27.3 days; the synodic month=29.5 days. (4) A lunar eclipse occurs when the Moon passes through the Earth's shadow. (5) A solar eclipse occurs when the Earth passes through the Moon's shadow. Planets, Greek Astronomy, Copernicus ------------------------------------ (1) Aristotle (4th cent BC) showed that the Earth is round. (2) Greek astronomers developed a geocentric model for the universe. (3) Ptolemy (2nd cent) used epicycles to explain retrograde motion of planers. (4) Copernicus (16th cent) proposed a heliocentric model for the universe. (5) In the model of Copernicus, retrograde motion is easily explained. Tycho, Kepler ------------- (1) Tycho Brahe made accurate measurements of planetary motion. (2) Planetary orbits are ellipses with the Sun at one focus. (3) A line between planet & Sun sweeps out equal areas in equal times. (4) The square of a planet's orbital period is proportional to the cube of its average distance from the Sun. Galileo ------------------------ (1) Galileo made telescopic observations supporting the heliocentric model, especially phases of Venus. Newton's Laws: -------------- Three Laws of Motion: (1) An object remains at rest, or moves in a straight line at constant speed, unless acted on by an outside force. (2) The acceleration of an object is directly proportional to force, and inversely proportional to mass. (3) For every action, there is an equal and opposite reaction. Law of Gravity: (4) The gravitational force between masses M and m, separated by distance r, is F=G(Mm/r^2) Applying Newton's Laws: ----------------------- (1) Newton modified and expanded Kepler's Laws of Planetary Motion. (2) Kepler described how planets move; Newton explained why they move. (3) Tides are caused by the difference between the Moon's gravitational force on different sides of the Earth. Light: ------ (1) Visible light is just one form of electromagnetic radiation. (2) Light can be though of as a wave or as a particle (photon). (3) Light forms a spectrum from short to long wavelengths. Temperature: ------------ (1) A hot, opaque object produces a continuous blackbody spectrum. (2) Stefan-Boltzmann Law and Wien's Law Matter: ------- (1) Atoms - basic structure (2) Atoms - energy levels (3) Isotopes and Radioactivity (4) Four forces of nature Spectra: -------- (1) A hot, transparent gas produces an emission spectrum. (2) A cool, transparent gas produces an absorption spectrum. (3) Every type of atom, ion, and molecule has a unique spectrum. (4) The most abundant elements in the universe are hydrogen and helium. (5) The radial velocity of an object is found from its Doppler shift. Telescopes: ---------- (1) Telescopes use either a lens or a mirror to gather light. (2) The main purposes of a telescope are to gather light and resolve detail. (3) Radio and microwave telescopes use a reflecting dish to focus waves. (4) Telescopes in orbit avoid the distorting effects of the atmosphere. (5) Ultraviolet, X-ray, gamma ray, and most infrared light is visible only from orbit. Solar System: Overview ----------------------- Age of the Earth ------------------ (1) The Earth is 4.6 billion years old; (2) Age of the Earth is determined using radioactive isotope dating; The Earth ---------- (1) The study of seismic waves tells us about the Earth's interior. (2) The Earth is layered into crust, mantle, inner core, and outer core. (3) The Earth is layered because it underwent differentiation when molten. (4) The lithosphere is broken into plates (16) that move relative to each other. (5) The motion of liquid metal in the outer core produces a magnetic field. Earth's Atmosphere ------------------ (1) The Earth's atmosphere consists mainly of nitrogen (N2) and oxygen (O2). (2) Without life, air would have no O2; without oceans, it would have much more CO2. (3) Excess CO2 can cause global warming via the greenhouse effect. Impacts ------- (1) Impacts played an essential role in the history of the Solar System. The Moon -------- (1) The Moon's surface has both smooth maria and cratered highlands. (2) The surface was shaped by heavy bombardment, followed by lava floods. (3) The Moon has a thick crust but a tiny (if any) iron-rich core. (4) The Moon most likely has been formed when a protoplanet struck the Earth. Mercury ------- (1) Mercury has a 3-to-2 spin-orbit coupling (not synchronous rotation). (2) Mercury has no permanent atmosphere because it is too hot. (3) Like the Moon, Mercury has cratered highlands and smooth plains. (4) Mercury has an extremely large iron-rich core. Venus ----- (1) The surface of Venus is hidden from us by clouds of sulfuric acid. (2) The atmosphere of Venus is hot because of a extreme (runaway) greenhouse effect. (3) The surface of Venus shows volcanic activity but no plate tectonics. (4) The interior of Venus is similar to that of the Earth. Mars ---- (1) Mars has a tenuous atmosphere, with little water vapor and few clouds. (2) Mar has large volcanoes and a huge rift valley, but no plate tectonics. (3) Robotic "rovers" and other probes have given us a close-up look at Mars. (4) Mars has two small irregular moons, Phobos and Deimos. Jupiter & Saturn ---------------- (1) Jupiter and Saturn consist mainly of hydrogen and helium. (2) Jupiter and Saturn have belts and zones of clouds, plus circular storms. (3) Jupiter and Saturn have strong magnetic fields created in metallic hydrogen. (4) Differences between Jupiter and Saturn are due to Jupiter's higher mass. Moons of Jupiter and Saturn --------------------------- The Galilean Moons of Jupiter: (1) Io: volcanically hyperactive (2) Europa: covered with smooth ice, with possible liquid water underneath (3) Ganymede: larger then Mercury (4) Callisto: heavily cratered The Giant Moon of Saturn: (5) Titan: wrapped in an atmosphere Rings of Giants Planets ----------------------- (1) All Jovian planets have rings (2) The rings are orbiting chunks of ice and dusty particles (3) Shepherd moons (4) Roche (tidal) radius Uranus and Neptune ------------------ (1) Uranus and Neptune are nearly identical in their internal structure. (2) The rotation axis of Uranus is tilted by about 90 degrees, causing extreme seasons. (3) Neptune has surprisingly strong storms, driven by internal heat. (4) Triton, the giant moon of Neptune, is a cold world with nitrogen geysers. Kuiper Belt ----------- (1) Pluto and its moon Charon are icy worlds that resemble Triton. (2) Eris, the troublemaker. (3) The Kuiper belt, beyond Neptune, contains small, icy, Pluto-like objects. (4) The icy Kuiper Belt Objects are leftover planetesimals. (5) The research on the Kuiper Belt continues. Comets ------ (1) Comets are "dirty snowballs": ice mixed with dust & carbon compounds. (2) When a comet is close to the Sun, it grows an ion tail and a dust tail; tail particles interact with Solar radiation and Solar wind; (3) Most comets are in the Kuiper belt or the Oort clod, far from the Sun. Asteroids --------- (1) Asteroids are mostly in the asteroid belt between Mars and Jupiter. (2) Asteroids are strongly influenced by the gravity of Jupiter. (3) Asteroids are made of rock, metal, or a combination of both. (4) Meteorites are usually asteroid fragments that have struck Earth. Planets Around Other Stars --------------------------- (1) Many planets have been found from the Doppler shift of their parent star. (2) Planets can be detected when they eclipse (or transit) their parent star. (3) More than 3000 planets have been found around stars other than the Sun; many more will be found soon. (4) Many planetary systems found so far are very different from the Solar System.