* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Our Solar System • BIG Idea: • Using the laws of motion and gravitation, astronomers can understand the orbits and the properties of the planets and other objects in the solar system. I. Models of the Solar System A. Geocentric (Earth-centered) model: the Sun, stars, and planets revolve around the Earth. – Aristotle promoted this Earth-centered model B. Heliocentric (Sun-centered) model: the Sun is the center of the universe - Copernicus proposed this Sun-centered model Kepler’s Laws: Explained planetary motion mathematically. 1. The orbits of planets are ELLIPSES (ovals) with the SUN at one FOCUS. • Because the planets’ orbits are elliptical, they are not always the same distances from the sun… – Do you remember the word to describe the point in our orbit when we are closest to the Sun? – Farthest away? 2. A planet must move more RAPIDLY when it is CLOSE to the sun and more SLOWLY when it is FAR from the sun. 3. Planets in LARGE orbits take much LONGER to orbit the sun than do planets in small orbits. • There are TWO types of planets in our solar system… • How were you taught to remember them? Planet Acronyms • My Very Excellent Mother Just Served Us Nachos • My Very Excellent Mother Just Served Us Noodles • My Very Educated Mother Just Served Us Nachos II. The Inner Planets (4 planets closest to the Sun) • Terrestrial Planets: Earth-like (rocky) A. Mercury • Closest to the Sun • Shortest orbit of 88 days • No atmosphere •Heavily cratered •Huge temperature range 427ºC in day, -173ºC at night Mariner 10 – visited the planet in 1974 and 1979 B. Venus •Hot surface: (464ºC) • Earth’s twin (size, mass, density) • Retrograde Rotation: •Dense clockwise (opposite atmosphere (96.5% CO2) that of all other planets) •Orbital period: 224.65 days •Slowest rotational period: 243 days •Brightest planet viewed from Earth •Pressure is 90xs that of Earth’s •Clouds of sulfuric acid •Trace amounts of water in atmosphere Magellan Probe C. Earth • • • • • Third planet from Sun Orbital period of 365.24 days Completes one full rotation in 23 hours 56 minutes Fifth largest planet Located between the Sun and the Asteroid Belt • One natural satellite: the moon Life on Earth is possible because… • …of the Earth’s distance from the Sun Temperature is warm enough for water to exist as a liquid Water occurs on Earth as a solid (ice), a liquid, or a gas (water vapor) The only known planet with the proper combination of water, temperature, and oxygen to support plant and animal life Earth’s Atmosphere D. Mars • • • • • Axis is tilted like Earth’s Orbit = 687 Earth days Rotation = 24 hours, 40 minutes Very thin atmosphere (mostly CO2) Olympus Mons – shield volcano Largest known volcano in our solar system 3X higher than Mt. Everest Viking 1 – first found evidence of water erosion III. The Outer Planets • Jovian Planets: Jupiter-like gas giants A. Jupiter • LARGEST planet • • • • • • Fastest rotation: every 10 hours Orbital period: 12 years Mostly hydrogen and helium More than 60 moons Largest moon in our solar system: Ganymede “Great Red Spot”: huge rotating storm (about 3 times the size of Earth); very cold (-260 degrees F) • 100 lbs. on Earth = 264 lbs. on Jupiter B. Saturn • • • • LOWEST density Average temperature: -176ºC Orbital period = 29.5 years Complex system of rings (ice) Cassini Spacecraft C. Uranus • Rotates horizontally • The ‘tipped’ planet • Orbital period = 84 years • Faint, rocky rings • Greenish color • Methane atmosphere • “Ice Giant” Voyager 2 D. Neptune • Orbital period = 164 years • 11 known satellites (moons) and possibly 4 rings • Upper atmosphere composed of white clouds of frozen methane (appear as bands moving between equator and poles) • “Great DARK Spot” violent swirling masses of gas (like a hurricane) – disappeared in 1994 • Solar system’s strongest winds – exceeding 1,000 km/hr IV. Other Solar System Objects A. Dwarf Planets: • • • • orbit the Sun, are not satellites (moons), are nearly round in shape, and have not cleared their orbits of smaller debris. 1. Pluto (now ‘asteroid #134340’) • Late to be discovered (1930) • Mostly frozen methane, rock, and ice • Demoted from planet status to “dwarf planet” in August 2006 Not always the furthest planet from the sun 2. Ceres: largest body in the Asteroid Belt 3. Eris: • • largest known dwarf planet 27% more massive than Pluto 4. Makemake 5. Haumea B. Small Solar System Bodies 1. Asteroids • thousands orbiting the Sun between Mars and Jupiter • rocky bodies • vary in diameter • pitted, irregular surfaces Asteroid Belt • between Mars and Jupiter • remains of unformed planets (planetesimals) meteoroid: small bits of rocks and metal left by a comet or asteroid collision meteor: bright streak of light produced by meteoroids burning up as they enter our atmosphere meteorite: meteoroid (or part of one) that is left after it hits the Earth • Meteor Shower “shooting stars” • Meteorite: meteoroid that makes it to Earth • When large meteorites strike Earth, they produce impact craters: • 2. Comets • small, icy bodies of rock, dust, methane and ammonia • orbit the Sun in long ellipses 1. Nucleus: small solid core, which is made up of rocks, metals, and ice 2. Tail: gas and dust In relation to the Sun, what do you notice about the tails of the comets? • The tails always point AWAY from the Sun! • Their tails of gas and dust are pushed away by radiation from the Sun.