Transcript Ch 20: A Family of Planets

Ch 20: A Family of Planets
Section 1: The Nine Planets
Measuring Interplanetary Distances
 Astronomical Unit (AU)—the average
distance between the Earth and the sun
 Distances within our solar system can be
measured in light minutes and light days
– Distances between stars are measured in light
years
The Inner Planets
 Inner planets also known as Terrestrial
Planets
 Closely Spaced Orbits
 Small, dense, rocky
 Includes: Mercury, Venus, Earth, Mars
Mercury
Mercury
 Closest to the sun
 Less gravity than Earth—You’d weigh 38% less!
 Extreme Temperature Differences
– From -173°C to 427°C
 1 Day = 59 Earth days (slow rotation)
 1 Year = 88 Earth days (fast revolution)
– For every 88 days (or 1.5 Mercurian days) Mercury
completes one revolution around the sun
Venus
Venus
 Earth’s twin
– Similar size, mass, and density
 Sun rises in west, sets in the east
– (rotates in opposite direction)
 Densest (thick) atmosphere of terrestrial planets
– Carbon dioxide (traps energy, causes greenhouse effect)
– Corrosive acids
 Surface temp. of 464° C
– Hottest surface of any planet!
 Very active surface
– Massive volcanoes and lava flows
Earth
Earth
 Constantly changing weather patterns
 Formed at just right distance from sun
– Temps allow water not to completely freeze or boil away
– Liquid water is the key to life!
 Astronauts study the effects of humans on the
environment
Mars
Mars
 The red planet
 Very cold
– Summer temps -13C to -77C
 Thin atmosphere
– Low air pressure adds to low temps—liquid water boils
away
 Frozen Water found on polar caps
– Evidence of liquid water in the past—Where did it go?
 Only 2 volcanic systems
– Tharsis Region—stretches 8000 km across planet
– Olympus Mons—Enormous extinct volcano
Outer Planets
 Differ greatly in size and composition from inner
planets
 All outer planets (except Pluto) are gas giants
– Large
– No solid surface
– All have rings
Jupiter
 Largest planet
 Very high pressures
– Metallic liquid hydrogen in core
 236% of Earth’s gravity
 Surface temp is -153° C
 Great red spot—storm system
– Diameter of spot is 1 ½ times Earth!
Saturn
 2nd largest planet
 Less dense than 1 g/cm³—it would float in water!
 Gives off lots of energy
 Known for its visible rings—brightest rings
– Made of icy and rocky particles
Uranus
 Blue-green disk
– Atmosphere made of methane—absorbs red part of sunlight
 Water and rock in interior
 2.7 light-hours from the sun
 Tilted on side—rotates sideways
– Hit by massive object
Neptune
 Farthest gas planet from the sun
 Great dark spot—storm system
 Fast Rotation
– 1 day is only 16 hours
 Neptune's winds are the fastest in the solar system,
reaching 2000km/hr!
Pluto
 Furthest from the sun
 Smallest planet
 Small, Icy, Dwarf planet
 Has not yet been visited by a spacecraft, but there's
one on the way!
 Scientists are still unsure as to exactly what it's made
of.
 Its orbit crosses Neptune’s, so its sometimes the 8th
planet