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