Ch 16.1-6: The Solar System Hmwk: M: a- I, k- q, s, t, w & x; MC: 1, 5-15; SA: 2, 3, 5-20. Astronomy the scientific study of the universe beyond Earth s atmosphere Universe everything, all energy, matter, and space The Milky Way one of 50 billion galaxies scattered throughout the universe Solar System complex system of moving masses around Sun held together by gravitational forces 8 major planets, over 170 moons, 4 dwarf planets, and 1000 s of other objects (asteroids, comets, meteoroids, etc.) Sun supplies the energy for nearly all life on the planet earth 1
5/6/14 Astronomers use EM radia;on to study Universe Planetary Mo;on Planet: Greek for wanderer Geocentric Model everything revolved around Earth (Ptolemy, AD 140) Heliocentric Model Sun-centered model (Copernicus: 1473-1543) Kepler s 1st Law Law of Elliptical Orbits Astronomical Unit (AU): average distance b/t Earth and Sun (1.5 x 108 km; 9.3 x 107 mi) 2
Major Planet Classifica;ons Sun 99.87% mass of solar system Of remaining 0.13%, Jupiter is > 50% Terrestrial (inner) Planets: Mercury, Venus, Earth & Mars High % of more massive (non-gaseous) elements (most H and He gone) Small size, rocky & metal composition, no rings Jovian (outer) Planets: Jupiter, Saturn, Uranus, & Neptune High % of less massive gaseous elements (most H and He remains) Rocky core composed of iron and silicates Thick layers of frozen methane, ammonia, and water above core 3
Revolu;on vs. Rota;on Revolve around Sun versus rotate on axis Counterclockwise: direct/prograde mokon Clockwise rotakon: retrograde (Venus and Uranus) ssize Comparison 4
Conjunc;on & Opposi;on and conjunckon with Mars Earth Facts Solid, spherical, rocky body w/ oceans & atmosphere (21% O 2 ) Large amounts of surface H 2 O: s, liq. & gas Unique: temperate climate, O 2 -containing atmosphere, and living organisms Oxidized environment: > 90%, by volume, of the rocks/minerals in Earth s crust contain oxygen Quartz SiO 2, Calcite CaCO 3, Feldspar KAlSi 3 O 8 Oblate spheriod: bulges at equator- rotation Pole Diameter ~ 43 km < Equatorial Diameter Small fraction since ave. dia. = 12,900 km 5
Albedo: fraction of sunlight reflected by object Earth: 33% (clouds, ice & water) Moon: 7% (brightest object in night sky) Venus: 76% (2 nd brightest in sky) Earth s Movement: Rota;on and Revolu;on Difficult to Prove RotaKon: Jean Foucault in 1851 (Foucault s Pendulum) 6
Revolution about Sun Parallax apparent motion, or shift, that occurs b/t two fixed objects when observer changes position Nearby stars appear to shift w/ respect to distant stars Used to determine distance to nearby stars 7
5/6/14 Mercury: named ajer the swij messenger of the Roman gods Shortest period of revolution: 88 days 3 rotations for every 2 revolutions Temperature range: +473oC to -173oC Practically no atmosphere Density close to Earth s Venus: Roman god of beauty Closest planet to Earth Surface not visible from Earth Thick CO2 clouds; Atmos: 96% CO2 90 atm; +477 C Most surface rocks volcanic Few impact craters 8
Mars: Roman God of War Two outstanding features: polar ice caps and extinct volcanoes Ice caps: frozen CO 2 (winter); CO 2(g) & H 2 O (s) (summer) Largest known volcano in solar system: 24 km high; ~3 X as big as Mauna Loa Red color: fine grain iron oxide minerals? Jupiter: Roman Supreme God Largest planet: vol. & mass; Dia.: 11 X Earth s 318 X more massive than Earth Average density: ~1.3 g/cm 3 Covered w/ thin layer of clouds composed of H, He, methane, ammonia, and several others Great Red Spot: erratic movement, shape, color, and size sometimes even disappearing Likely a huge counterclockwise hurricane-like storm, lasting hundreds of years ~10 hour days 9
Saturn: Roman God of Agriculture Saturn Three prominent rings, seven distinct rings Most of any Jovian planet Rings inclined 27 o to orbital plane Rings thought to be composed of ice and icecoated rocks (micrometers à 10 m) Most spectacular sight that can be viewed from Earth with a small telescope Diameter is 9 times Earth s -- 95 times more mass than Earth Average density of only 0.7 g/cm 3 10
Uranus: named ajer father of Titans and grandfather of Jupiter Thin ring system composed of boulder-size particles (>1m) Average density: only 1.3 g/cm 3 Revolves around Sun on its side Rotates in a retrograde fashion Neptune: Roman God of the Sea Existence predicted due to Uranus motion Large dark spot similar to Jupiter: thought to be due to large wind systems Neptune and Uranus are similar in size and in the composition of their atmospheres Two planets often considered twins 11
Designations of Celestial Bodies International Astronomical Union (IAU) In 2006 the IAU adopted the following criteria for a solar system body to be a planet: (1) It must be in orbit about the Sun. (2) It must have sufficient mass for self-gravity to form a nearly round shape. (3) It must be the dominant body within its orbit. Pluto s orbit goes inside of Neptune s orbit- not planet Two new categories: 1) Dwarf planets: Pluto, Ceres and Eris 2) Small solar-system bodies: Kuiper Belt (beyond Neptune & into Ceres orbit) and asteroid belts 12
Ceres (goddess of agriculture): 1 st Dwarf Planet from Sun Lies in asteroid belt between Mars and Jupiter Diameter of 940 km- smallest dwarf planet Pluto (god of outer darkness): 2 nd Dwarf Planet from Sun Average density: 1.65 g/cm 3 Does not resemble either terrestrial or Jovian Planets Eris (goddess of chaos & strife): 3 rd Dwarf Planet from Sun Previously known as 2003 UB313 (or Xena) Slightly larger & ~3 X farther away from Sun than Pluto Highly elliptical orbit- takes 560 Earth yrs for one revolution Haumea mass 30% of Pluto and orbits at 43 AU Makemake mass 75% of Pluto and orbits at 75 AU Edge of Universe: ~100 AU 13