The Planets & the Solar System
Chapter 27300
The Solar SystemThe Inner Planets Ch. 27.1
• 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 earth-like 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
– No atmosphere (due to weak gravity)…
» So… no weather to erode craters
• smooth plains– formed by lava flowing from
cracks in surface
– extremely hot day temps (400+°C) & extremely cold night temps (-200°C)• due to lack of atmosphere
MESSENGER Orbits Mercury (AMNH Sci Bulletin)
• Venus– “Earth’s twin/sister planet”
• similar diameter, mass, gravity
– Unlike other planets rotates east to west (clockwise)
– atmosphere = mostly carbon dioxide (CO2)
• “runaway” greenhouse effect (~475°C)
– yellow clouds = sulfuric acid
Inner Planets: Fun Facts
• Mars– Axis tilted at almost
same angle & in same direction as Earth’s
• similar 4 seasons but ~2x as long (since year is ~2x longer than Earth’s)
– largest volcano in the solar system = Olympus Mons
– Valles Marineris canyon system (as long as U. S. is wide)
Inner Planets: Fun Facts
Curiosity: Searching for Carbon (AMNH Sci Bulletin)
• Jupiter– 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– less dense than water
(1g/cm3)• 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
Saturn System Is Showing Its Age (AMNH Sci Bulletin)
How Did Saturn Get Its Rings? (AMNH Sci Bulletin)
• Uranus– inclination (tilt) of axis
almost 90°• So… rotates on its side
– May have been tipped by collision early in history of solar system
– blue tint from methane
Outer Planets: Fun Facts
• Neptune– 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– No longer “true” planet
• Now one of 40+ “dwarf” planets– Not dense enough to be “terrestrial”
& too small to be “Jovian”.– Smaller than 7 moons in our solar
system (including our moon)
– New Horizons probe to Pluto launched Jan. 2006• will fly by Pluto & Charon ~2015
Outer Planets: Fun Facts
Article on Why Pluto is No Longer Considered a Planet
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
Nile-Like River Found on Moon of Saturn (AMNH Sci Bulletin)
• What are comets?– “dirty snowballs”
• dust particles trapped in mixture of frozen water, carbon dioxide, methane, & ammonia
• Where are comets usually found?– Most are Trans-Neptunian
Objects (TNOs)• spend most of their time
beyond Neptune’s orbit– Including in Kuiper Belt & Oort Cloud
Solar System Debris Ch. 27 Sec. 4
• A few comets have highly elliptical orbits taking them closer to the sun– can become visible at night
when icy surface is heated• Forms coma (cloud of gas &
dust that expands into space)– tail points away from sun due
to solar wind
– Halley’s Comet• 76 years
– Comet Ison
Solar System Debris
http://news.discovery.com/space/astronomy/comet-ison-barely-survives-thanksgiving-solar-roast-131129.htm
• 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 DebrisProtecting Earth from Asteroid Impacts (AMNH Sci Bulletin)
• 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
Solar System Debris
• What are the 3 basic types of meteorites?– stony
– iron
– stony-iron
• Give info about:– how solar
system evolved– possible effects
of impacts
Solar System Debris
Willamette Meteorite
Cape York Meteorite
(Ahnighito)
• What are impact craters?– bowl-shaped depressions
that remain after meteor or other object hits Earth, other planet, moon
• ejecta (debris) rays radiate out from crater
Solar System DebrisArizona’s Barringer Meteor Crater