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Chapter 28 Notes
Our Solar System
Our Solar System
The Inner Planets (and Pluto)
All the Planets (and Pluto)
The Planets and the Sun (and Pluto)
Formation of the Solar System
• Nebular Theory:a)Interstellar cloud
contracts and spinsb)Dense center begins
nuclear fusion (sun)c) Remaining material
forms planetesimals and then planets
Historical Solar System Models
• Geocentric (Earth-centered) model– One problem was how to explain
retrograde motion
• Copernicus’ heliocentric model– 1543, Polish scientist– Planets (including Earth) orbit the
Sun in circular orbits– Supporting evidence collected by
Tycho Brahe
Kepler’s laws of planetary motion
• Johannes Kepler inherited Tycho’s data after his unexpected death.
Galileo
• First person to use a telescope to observe the sky
• Discovered moons orbiting Jupiter• Also observed sun spots, phases of Venus, and
Moon craters
Newton and Gravity
• Newton’s discovery of the law of universal gravitation provided an explanation for the heliocentric model of the solar system
Zone 1: Inner Planets
• Terrestrial: “Earth-like”• Small • Composed of rock (high density)• Close to the Sun• Few or no moons• No rings
Mercury
• Smallest• Closest to the Sun • No moons • No atmosphere• Cratered like the Moon• 1 orbit = 1.5 rotations (2 years = 3 days)
Venus
• No moons• Earth’s “twin” in size• Rotates backwards• 1 day = 243 Earth days• Very high CO2 concentration in the atmosphere
causes super greenhouse effect• Surface temperature of 464C!!• Can be seen as a bright morning or evening “star”
Earth
• One moon• Tectonically active• O2 in atmosphere
• Water exists in all 3 phases• Mild greenhouse effect to
keep the planet warm enough for life
Mars
• The red planet• CO2 atmosphere
• 2 moons (Phobos and Deimos)• Has seasons like Earth, but a year is twice as
long• Largest volcano in the solar system: Olympus
Mons• Once had liquid water, has polar CO2 ice caps
Outer Planets
• Gas giants or “Jovian”: Jupiter-like• Large• Low density • Lots of moons• All have ring systems• Far from the Sun
Jupiter
• Largest planet• Banded appearance• Great red spot• Faint ring system• 4 large moons, more than 60 total• Rapid rotation (10 hours = 1 day); shortest day
of all the planets
Saturn
• Famous for ring system• More than 55 moons• Density lower than water• Largest moon, Titan, has an atmosphere of
nitrogen and methane• Another moon, Enceladus, shows evidence of
geologic activity
Uranus
• Discovered in 1781• Rotational axis is 98• At least 27 moons• Rings are dark and nearly
invisible• Appears blue because of
the way it reflects light
Neptune
• Discovered 1846• 13 moons• Distinctive clouds and belts• Predicted before it was discovered• 6 rings composed of dust particles• Largest moon, Triton, orbits backwards
Other Solar System Objects
• Dwarf planets• Asteroids• Kuiper belt objects (KBOs)• Comets (the Oort cloud)