The Planets & the Solar System Chapter 27

The Solar System Ch. 27 Sec 1 What are the 2 “planetary neighborhoods”? –inner planets –outer planets What separates these 2 “neighborhoods?” –asteroid belt

What are the inner planets? –4 closest to sun Mercury Venus Earth Mars –What is another name for the inner planets? “terrestrial” planets –b/c earthlike characteristics »rocky crusts »dense mantle layers »very dense cores Distance Between Planets Visualization The Solar System

What are asteroids? –solid, rocklike masses that orbit the sun in same direction as planets Where are asteroids located? –between Mars & Jupiter in asteroid belt that separates inner planets from outer planets The Solar System

What are the outer planets? –remaining 4 planets Jupiter Saturn Uranus Neptune What is another name for the outer planets? –“Jovian” planets or Gas Giants How do they compare to the terrestrial planets? –considerably larger than Earth –gaseous –less dense –have ring systems The Solar System

What about Pluto??? –oddity of the solar system Not dense enough to be considered “terrestrial”. Too small to be “Jovian”. The Solar System

Inner Planets: Fun Facts Mercury –surface = many craters & smooth plains formed by lava flowing from cracks in surface –extremely hot day temps (400+°C) & extremely cold night temps (-200°C) –no atmosphere b/c weak gravity

Venus –“Earth’s twin/ sister planet” similar diameter, mass, & gravity –Unlike other planets  rotates from east to west (clockwise) –day (243 Earth days) is longer than year (225 Earth days) –atmosphere = mostly carbon dioxide (CO 2 ) “runaway” greenhouse effect (~475°C) –yellow clouds = sulfuric acid Inner Planets: Fun Facts

Mars (4 th from sun) –1 st planet outside Earth’s orbit –period of rotation  1 day = ~24 ½ hrs –period of revolution (orbit)  1 yr = 687 Earth days …~2x as long as Earth’s year –Axis tilted at almost same angle & in same direction as Earth’s similar 4 seasons but ~2x as long –largest volcano in the solar system Olympus Mons –Valles Marineris canyon system (as long as the United States is wide) Inner Planets: Fun Facts

Jupiter (5 th from sun) –Largest planet More than 2x mass of all other planets combined –Colored zones & belts –“ Great Red Spot” May be calm area that rotates slowly in turbulent atmosphere Outer Planets: Fun Facts Ch. 27 Sec. 2

Saturn (6 th from sun) –lowest density (0.7 g/cm 3 ) less dense than water (1g/cm 3 ) –would float –most visible ring system believed to be chunks of ice –colored zones & belts rising & sinking gases fewer than Jupiter Outer Planets: Fun Facts

Uranus (7 th from sun) –inclination (tilt) of axis almost 90° So… rotates on its side May have been tipped by collision with Earth-sized mass early in history of the solar system –Methane gives it its blue tint Outer Planets: Fun Facts

Neptune (8 th from sun) –most distant Jovian planet occasionally outside Pluto’s orbit –b/c Pluto’s orbit sometimes brings Pluto closer to the sun than Neptune –Astronomers predicted existence mathematically in 1846 Outer Planets: Fun Facts

Pluto (9 th from sun) –occasionally 8 th “planet” b/c orbit sometimes brings it closer to Sun than Neptune –Smallest “planet” Smaller than 7 moons in our solar system (including our moon) –Pluto & Charon (one of its moons) are similar in mass »some scientists consider them to be a “double planet” rather than a planet- moon system Outer Planets: Fun Facts

Pluto (continued) –New Horizons probe to Pluto launched Jan will fly by Pluto and Charon –Will take advantage of Jupiter's gravity (planned 2007 flyby) which will boost the probe's velocity by 9,000 mph & get it to Pluto by 2015 –CBS Video of Pluto ProbeCBS Video of Pluto Probe –No longer considered a “true” planet Now considered one of over 40 “dwarf” planets –Article on Why Pluto is No Longer Considered a PlanetArticle on Why Pluto is No Longer Considered a Planet Outer Planets: Fun Facts

Planetary Satellites Ch. 27 Sec. 3 What is a satellite? –an object that orbits a planet –Example of natural satellites? moons –Example of artificial satellite? TV satellite, GPS satellite, etc.

Earth  moon = only natural satellite Mars  2 tiny irregularly shaped moons –Phobos –Deimos Jupiter  at least 63 moons –4 largest Galilean satellites (in honor of discoverer Galileo) –Io –Europa –Ganymede –Callisto Planetary Satellites

Saturn  at least 61 moons –Titan only moon known to have substantial atmosphere Uranus  at least 27 moons –5 major moons Titania Oberon Umbriel Ariel Miranda Neptune  at least 13 moons –Triton Planetary Satellites

What are comets? –“dirty snowballs” dust particles trapped in mixture of frozen water, carbon dioxide, methane, & ammonia Where are comets usually found? –spend most of their time beyond Neptune’s orbit consist only of solid main body (nucleus) What are Trans-Neptunian Objects (TNOs)? –orbit beyond Neptune in Kuiper Belt & Oort Cloud Solar System Debris Ch. 27 Sec. 4

comets (continued) –A few comets have highly elliptical orbits that take them closer to the sun can become visible at night Energy from the sun heats the comet’s icy surface –Forms a coma (cloud of gas & dust that expands into space) –solar wind pushes coma into space forming tail pointing away from the sun –Halley’s Comet (after astronomer Edmund Halley who noticed & predicted pattern of return) 76 years Solar System Debris

What are asteroids? –solid, rocklike masses probably left over from formation of solar system How do asteroids orbit? –around sun in same direction as planets most have nearly circular orbits within asteroid belt between Mars & Jupiter Solar System Debris

What are meteors, meteoroids, & meteorites? –rocky or icy fragments; smaller than asteroids meteoroid  traveling in space meteor  passing through Earth’s atmosphere –“shooting star” meteorites  hit Earth’s surface –What are the 3 basic types? »stony »iron »stony-iron Solar System Debris

What are impact craters? –bowl-shaped depressions that remain after meteor or other object hits Earth, other planet, moon one of best known = Arizona’s Barringer Meteor Crater Solar System Debris