Astronomy 1140 -- Autumn 2018 (Prof. Stanek) Midterm 3 Study Guide (Wednesday, Nov 16) ------------------------------------------ There will be 50 questions on the Midterm Exam, which will count for 19% of the final grade. As an option, we allow one "help sheet" (one standard 8.5x11 piece of paper, both sides can be used) of self-prepared notes to be used during this exam. Please bring your OSU ID with you. Classes to review - all classes between October 10 and November 9: 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 Rings of Giants Planets Uranus & Neptune Pluto and the Kuiper Belt Comets Asteroids Key Concepts: 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.