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: Interstellar cloud contracts and spins Dense center begins nuclear fusion (sun) 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 464C!! 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)